Thesis (M.S.)--Oregon State University, 1999. / Typescript (photocopy). Includes bibliographical references. Also available online.

Over 10% of the world’s land is salt affected. Salt accumulation is a major soil constraint for agricultural sustainability in arable or newly cultivated soils. As a result of salinity, soil chemical, physical and biological properties deteriorate, plant uptake of water and nutrients, particularly P, decreases and plant growth declines. Application of plant residues can enhance the activity of soil microorganisms, the availability of nutrients, including P and the plant uptake of P and growth. Such a practice can also be economically viable as it can reduce the use of P from inorganic sources, maintaining the world’s reserve of P rocks and reducing the price of fertilizers and the environmental pollution often associated with the excessive application of inorganic N and P fertilizers. Little is known about how P, with N in proper form, added from inorganic and/or residue sources can affect wheat growth in the salt affected soils with no confounding pH or sodium adsorption ratio (SAR). Increasing microbial activity, N and P availability and wheat uptake of P by application of N and P from organic and inorganic sources may improve wheat growth and hence productivity under saline conditions. The overall aim of this study was to determine ways for enhancing the activity of microorganisms and increasing the availability of N and P, the uptake of nutrients, particularly P and the growth of wheat by management of fertilization from inorganic and organic sources in saline soils. This study therefore was conducted with the following aims: 1) to investigate the relationship between salinity and P availability; 2) to assess wheat response to combined application of N and P fertilizers under saline conditions; 3) to evaluate the effect of plant residue addition on N and P availability and microbial activity in salt affected soils; 4) to determine microbial response to addition of inorganic N rate and form, and how this will affect N and P availability in a saline soil, and 5) to determine the effect of P added from inorganic fertilizer and plant residue, compared to inorganic P fertilization, on microbial biomass and wheat nutrient composition and growth in a saline soil. In saline soils, P availability can be affected by the salt type and concentration and soil texture. Three experiments were conducted to study the relationship between P availability, soil texture and salinity. The results of the first experiment in which soil was shaken with different concentrations of NaCl or CaCl2 or Na2SO4, indicated that P solubility decreased with increasing concentration of Ca2+, but was not affected by Na+ salts. In the second experiment, P availability (after 24h shaking) decreased with increasing salt concentration up to EC1:5 3.1 dS m-1, increased with increasing P addition (0, 100, 200, 400, 600, 1200, 2500 and 5000 µg P g-1 soil), and was generally higher in sandy soil than in sandy loam soil. In the third experiment (15 days incubation), it was found that P availability significantly decreased one day after P addition which was followed by a further decrease to day 5, but then remained unchanged until day 15. It can be concluded that P availability is reduced in presence of clay, and decreases with increasing concentration of salts, particularly Ca2+, and that the availability of P stabilizes in sandy and sandy loam soils within 2 weeks after addition of P from inorganic source. Increasing N or P fertilization enhanced wheat growth in salt affected soils. Therefore combined application of N and P may enhance wheat growth in saline-non sodic soils with neutral pH. Three glasshouse experiments were carried out with the aim to determine the salinity range to be used in the subsequent experiments and to test the hypothesis that combined addition of N and P fertilizers can enhance wheat growth in a sandy loam soil with low SAR and neutral pH. The first two experiments were conducted in a sandy loam salinized to EC1:5 of 0.18, 1.36, 2.00 and 2.67 dS m-1 using NaCl and CaCl2. The wheat varieties Janz and Krichauff died in all soils to which salt was added showing that these EC levels were too high. The third experiment was conducted with Krichauff in the sandy loam soil with EC1:5 0.19, 0.32, 0.49, 0.67 and 0.86 dS m-1, equivalent to ECe 2.2, 4.4, 6.7, 9.2 and 11.8 dS m-1, respectively, and with 0, 30 and 60 mg P kg-1 soil and 50, 100 and 200 mg N kg-1 soil. Salinity reduced plant dry matter at all N and P application rates. Increasing N application rates decreased growth at low and high salinity, whereas increasing P addition improved growth at all salinity levels. The highest shoot and root dry weights were obtained with 50 mg N and 60 mg P kg-1 soil. Nitrogen and P fertilization did not increase wheat growth in soil with greater than EC1:5 0.67 dS m-1, equivalent to ECe 9.2 dS m-1. Plants are known to respond differently to N form. A glasshouse experiment was carried out to assess the effect of N form (NH4 +, NO3 - or NH4NO3) added at 50, 100 and 200 mg kg-1 soil, in addition to the control (no N), on nutrient composition and growth of Krichauff in a sandy loam soil with EC1:5 0.21, 0.48 and 0.86 dS m-1, equivalent to ECe 2.8, 6.6 and 11.8 dS m-1. Increasing soil salinity decreased shoot and root dry weights and shoot macro- and micronutrient concentrations with all forms of N. At every N addition rate and with increasing N addition from N50 to N200, compared to NH4 +, the salinity of soil solution was far higher with NO3 - and lowest with NH4NO3. Shoot and root dry weights were highest with addition of 50 mg NO3-N or 100 mg NH4-N or as NH4NO3 at all salinity treatments. Concentrations of shoot P, Fe, Mn and Zn concentrations were greater with NH4 + and NH4NO3 compared to NO3 -, but concentrations of shoot K and Ca were higher with NO3 - than with NH4 + nutrition at all salinity treatments. At a given N rate, shoot and root dry weights were greatest with NH4NO3 in the saline sandy loam soil with up to EC1:5 0.67 dS m-1. Two experiments were conducted to evaluate the effect of plant residue addition on microbial activity and biomass, and N and P availability in salt affected soils. Although the same amounts of Na+ and Ca2+ salts, EC1:5 differed between tested soils due to differences between soils in clay content and water holding capacity. The first experiment aimed to assess the salinity range for microbial activity over 2 weeks in saline soils with different texture amended with glucose/nitrate (C/N ratio 16:1). The EC1:5 were 0.2, 1.26, 1.83, 2.28 and 2.99 dS m-1 in the silty loam, 0.16, 1.10, 1.98, 2.33 and 3.18 dS m-1 in the sand and 0.19, 0.82, 1.75, 2.03 and 2.79 dS m-1 in the sandy loam. Soil respiration significantly decreased with increasing salinity in the glucose/nitrate amended soils, but was not completely inhibited even at highest salinity treatment. Cumulative CO2-C increased over 2 weeks and was highest in the silty loam soil and decreased in the following order: silty loam soil < sandy loam soil < sandy soil. The second experiment was conducted to determine the effect of three different plant residues added at 2% (w/w) on microbial biomass and N and P availability over time (70 days) in saline sandy and sandy loam soils with low SAR and neutral pH. The EC1:5 was 0.21, 1.08, 1.90, 2.63 and 2.89 dS m-1 in the sand and 0.19, 0.87, 1.63, 2.32 and 2.49 dS m-1 in the sandy loam. Microbial biomass C, N and P decreased with increasing soil salinity and were highest on day 10. With residue addition, microbial biomass C and P were significantly higher in the sandy than in the sandy loam soil, whereas no significant differences were found between soils for microbial biomass P at all salinity treatments. Under all salinity treatments, compared to other residues, highest biomass N was found in canola-amended sandy loam and in lupin-amended sandy soils. With increasing soil salinity, highest microbial P was found in the sandy soil amended with lupin residue. Nitrogen availability was generally higher in the sandy soil than in the sandy loam soil, whereas the opposite was found for P availability. Compared to canola and lucerne, N and P availability were highest in lupin amended sandy and sandy loam soil. Two experiments were conducted to assess whether N addition (rate and form) can affect the microbial activity in presence of residues in a saline sandy loam soil. The first experiment aimed to evaluate the effect of N rate (0, 25, 50 and 100 mg N kg-1 soil) added as NO3 - on soil respiration over 2 weeks under non-saline conditions in presence of 2% lupin residues. The second was to determine the effect of N added at 50 mg N kg-1 soil as NH4 + or NO3 - and lupin residue added at 2 and 4% (w/w) on microbial activity and biomass and N and P availability over 45 days in a sandy loam soil with EC1:5 0.21, 0.51 and 0.85 dS m-1, equivalent to ECe 2.8, 7.0 and 11.7 dS m-1. Soil respiration and cumulative respiration were not significantly affected by N application rate over 2-week-incubation under non-saline conditions. Microbial biomass and N and P availability decreased with increasing salinity and were highest at 4% lupin residue. Soil respiration rate and cumulative CO2-C and microbial biomass C, N and P were greater with addition of 50 mg N kg-1 soil as NO3-N compared to NH4-N at every addition rate of lupin residues under saline conditions. Soil microbial biomass C, N and P were highest on day 15 and decreased over time, whereas N and P availability were lowest on day 15 and increased over time. Since addition of inorganic N and P fertilizers improved the growth of wheat (cv Krichauff) in the saline sandy loam soil at SAR 1 and neutral pH, two glasshouse experiments were conducted to determine the effects of plant residue addition on the nutrition of wheat. The first experiment was conducted under non-saline condition to determine the effect of lupin residue rate (2% and 4% w/w) on wheat growth. The second experiment was conducted under saline conditions to determine the effect of P added as lupin residue (2%) and/or KH2PO4 (0, 20 and 40 mg P kg-1 soil) with and without 50 mg N kg-1 soil added as (NH4)2.SO4 on microbial biomass, N and P availability, plant growth and nutrient composition in the saline sandy loam soil. The EC1:5 were 0.23, 0.35 and 0.51 dS m-1, equivalent to ECe 3.1, 4.8 and 7.0 dS m-1, respectively. In the first experiment under non-saline conditions, shoot dry weight was lower with addition of 4% than with 2% lupin residue with and without inorganic N. In the second experiment under saline conditions, microbial biomass C and N increased with increasing application of inorganic P, but was not as much as in presence of lupin residues. In presence of lupin residue, wheat growth increased with increasing addition of inorganic P under saline conditions. Compared to the soil with P from inorganic fertilizer and residues, inorganic P increased shoot and root dry weights and shoot P, K, Mn and Zn concentrations, but not N concentration. Addition of 50 mg inorganic N in presence of lupin residues significantly increased N and P availability and microbial biomass, but had no significant effect on wheat growth in a saline sandy loam soil. The results showed that optimal application of N and P organic and inorganic fertilizers can improve N and P availability, microbial activity and wheat growth in salt affected soils. Highest wheat dry weight was achieved by application of 60 mg P kg-1 soil in a sandy loam soil with EC1:5 0.67 dS m-1, equivalent to ECe 9.2 dS m-1. Wheat growth was also improved with application of N-NH4 + or as NH4NO3 at 100 mg N kg-1 soil. These N and P fertilization rates can potentially enhance wheat growth in the sandy loam soil with up to EC1:5 0.67 dS m-1, but with SAR 1 at neutral pH. Plant residues increased microbial activity and N and P availability in the saline soils. In the soils used here, with residue addition wheat growth was P limited due to competition with microorganisms for available P. Therefore application of residues with inorganic P is necessary to satisfy wheat requirements of N and P in the saline sandy loam soil. In the saline sandy loam soil at SAR 1 and neutral pH, application of 2% lupin residues and 40 mg KH2PO4-P kg-1 soil achieved highest microbial biomass, nutrient availability and wheat growth. However, wheat growth with these rates is not as high as with inorganic P at similar rate due to micronutrient deficiency in the saline soil with lupin residues. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1331419 / Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2008

Over 10% of the world’s land is salt affected. Salt accumulation is a major soil constraint for agricultural sustainability in arable or newly cultivated soils. As a result of salinity, soil chemical, physical and biological properties deteriorate, plant uptake of water and nutrients, particularly P, decreases and plant growth declines. Application of plant residues can enhance the activity of soil microorganisms, the availability of nutrients, including P and the plant uptake of P and growth. Such a practice can also be economically viable as it can reduce the use of P from inorganic sources, maintaining the world’s reserve of P rocks and reducing the price of fertilizers and the environmental pollution often associated with the excessive application of inorganic N and P fertilizers. Little is known about how P, with N in proper form, added from inorganic and/or residue sources can affect wheat growth in the salt affected soils with no confounding pH or sodium adsorption ratio (SAR). Increasing microbial activity, N and P availability and wheat uptake of P by application of N and P from organic and inorganic sources may improve wheat growth and hence productivity under saline conditions. The overall aim of this study was to determine ways for enhancing the activity of microorganisms and increasing the availability of N and P, the uptake of nutrients, particularly P and the growth of wheat by management of fertilization from inorganic and organic sources in saline soils. This study therefore was conducted with the following aims: 1) to investigate the relationship between salinity and P availability; 2) to assess wheat response to combined application of N and P fertilizers under saline conditions; 3) to evaluate the effect of plant residue addition on N and P availability and microbial activity in salt affected soils; 4) to determine microbial response to addition of inorganic N rate and form, and how this will affect N and P availability in a saline soil, and 5) to determine the effect of P added from inorganic fertilizer and plant residue, compared to inorganic P fertilization, on microbial biomass and wheat nutrient composition and growth in a saline soil. In saline soils, P availability can be affected by the salt type and concentration and soil texture. Three experiments were conducted to study the relationship between P availability, soil texture and salinity. The results of the first experiment in which soil was shaken with different concentrations of NaCl or CaCl2 or Na2SO4, indicated that P solubility decreased with increasing concentration of Ca2+, but was not affected by Na+ salts. In the second experiment, P availability (after 24h shaking) decreased with increasing salt concentration up to EC1:5 3.1 dS m-1, increased with increasing P addition (0, 100, 200, 400, 600, 1200, 2500 and 5000 µg P g-1 soil), and was generally higher in sandy soil than in sandy loam soil. In the third experiment (15 days incubation), it was found that P availability significantly decreased one day after P addition which was followed by a further decrease to day 5, but then remained unchanged until day 15. It can be concluded that P availability is reduced in presence of clay, and decreases with increasing concentration of salts, particularly Ca2+, and that the availability of P stabilizes in sandy and sandy loam soils within 2 weeks after addition of P from inorganic source. Increasing N or P fertilization enhanced wheat growth in salt affected soils. Therefore combined application of N and P may enhance wheat growth in saline-non sodic soils with neutral pH. Three glasshouse experiments were carried out with the aim to determine the salinity range to be used in the subsequent experiments and to test the hypothesis that combined addition of N and P fertilizers can enhance wheat growth in a sandy loam soil with low SAR and neutral pH. The first two experiments were conducted in a sandy loam salinized to EC1:5 of 0.18, 1.36, 2.00 and 2.67 dS m-1 using NaCl and CaCl2. The wheat varieties Janz and Krichauff died in all soils to which salt was added showing that these EC levels were too high. The third experiment was conducted with Krichauff in the sandy loam soil with EC1:5 0.19, 0.32, 0.49, 0.67 and 0.86 dS m-1, equivalent to ECe 2.2, 4.4, 6.7, 9.2 and 11.8 dS m-1, respectively, and with 0, 30 and 60 mg P kg-1 soil and 50, 100 and 200 mg N kg-1 soil. Salinity reduced plant dry matter at all N and P application rates. Increasing N application rates decreased growth at low and high salinity, whereas increasing P addition improved growth at all salinity levels. The highest shoot and root dry weights were obtained with 50 mg N and 60 mg P kg-1 soil. Nitrogen and P fertilization did not increase wheat growth in soil with greater than EC1:5 0.67 dS m-1, equivalent to ECe 9.2 dS m-1. Plants are known to respond differently to N form. A glasshouse experiment was carried out to assess the effect of N form (NH4 +, NO3 - or NH4NO3) added at 50, 100 and 200 mg kg-1 soil, in addition to the control (no N), on nutrient composition and growth of Krichauff in a sandy loam soil with EC1:5 0.21, 0.48 and 0.86 dS m-1, equivalent to ECe 2.8, 6.6 and 11.8 dS m-1. Increasing soil salinity decreased shoot and root dry weights and shoot macro- and micronutrient concentrations with all forms of N. At every N addition rate and with increasing N addition from N50 to N200, compared to NH4 +, the salinity of soil solution was far higher with NO3 - and lowest with NH4NO3. Shoot and root dry weights were highest with addition of 50 mg NO3-N or 100 mg NH4-N or as NH4NO3 at all salinity treatments. Concentrations of shoot P, Fe, Mn and Zn concentrations were greater with NH4 + and NH4NO3 compared to NO3 -, but concentrations of shoot K and Ca were higher with NO3 - than with NH4 + nutrition at all salinity treatments. At a given N rate, shoot and root dry weights were greatest with NH4NO3 in the saline sandy loam soil with up to EC1:5 0.67 dS m-1. Two experiments were conducted to evaluate the effect of plant residue addition on microbial activity and biomass, and N and P availability in salt affected soils. Although the same amounts of Na+ and Ca2+ salts, EC1:5 differed between tested soils due to differences between soils in clay content and water holding capacity. The first experiment aimed to assess the salinity range for microbial activity over 2 weeks in saline soils with different texture amended with glucose/nitrate (C/N ratio 16:1). The EC1:5 were 0.2, 1.26, 1.83, 2.28 and 2.99 dS m-1 in the silty loam, 0.16, 1.10, 1.98, 2.33 and 3.18 dS m-1 in the sand and 0.19, 0.82, 1.75, 2.03 and 2.79 dS m-1 in the sandy loam. Soil respiration significantly decreased with increasing salinity in the glucose/nitrate amended soils, but was not completely inhibited even at highest salinity treatment. Cumulative CO2-C increased over 2 weeks and was highest in the silty loam soil and decreased in the following order: silty loam soil < sandy loam soil < sandy soil. The second experiment was conducted to determine the effect of three different plant residues added at 2% (w/w) on microbial biomass and N and P availability over time (70 days) in saline sandy and sandy loam soils with low SAR and neutral pH. The EC1:5 was 0.21, 1.08, 1.90, 2.63 and 2.89 dS m-1 in the sand and 0.19, 0.87, 1.63, 2.32 and 2.49 dS m-1 in the sandy loam. Microbial biomass C, N and P decreased with increasing soil salinity and were highest on day 10. With residue addition, microbial biomass C and P were significantly higher in the sandy than in the sandy loam soil, whereas no significant differences were found between soils for microbial biomass P at all salinity treatments. Under all salinity treatments, compared to other residues, highest biomass N was found in canola-amended sandy loam and in lupin-amended sandy soils. With increasing soil salinity, highest microbial P was found in the sandy soil amended with lupin residue. Nitrogen availability was generally higher in the sandy soil than in the sandy loam soil, whereas the opposite was found for P availability. Compared to canola and lucerne, N and P availability were highest in lupin amended sandy and sandy loam soil. Two experiments were conducted to assess whether N addition (rate and form) can affect the microbial activity in presence of residues in a saline sandy loam soil. The first experiment aimed to evaluate the effect of N rate (0, 25, 50 and 100 mg N kg-1 soil) added as NO3 - on soil respiration over 2 weeks under non-saline conditions in presence of 2% lupin residues. The second was to determine the effect of N added at 50 mg N kg-1 soil as NH4 + or NO3 - and lupin residue added at 2 and 4% (w/w) on microbial activity and biomass and N and P availability over 45 days in a sandy loam soil with EC1:5 0.21, 0.51 and 0.85 dS m-1, equivalent to ECe 2.8, 7.0 and 11.7 dS m-1. Soil respiration and cumulative respiration were not significantly affected by N application rate over 2-week-incubation under non-saline conditions. Microbial biomass and N and P availability decreased with increasing salinity and were highest at 4% lupin residue. Soil respiration rate and cumulative CO2-C and microbial biomass C, N and P were greater with addition of 50 mg N kg-1 soil as NO3-N compared to NH4-N at every addition rate of lupin residues under saline conditions. Soil microbial biomass C, N and P were highest on day 15 and decreased over time, whereas N and P availability were lowest on day 15 and increased over time. Since addition of inorganic N and P fertilizers improved the growth of wheat (cv Krichauff) in the saline sandy loam soil at SAR 1 and neutral pH, two glasshouse experiments were conducted to determine the effects of plant residue addition on the nutrition of wheat. The first experiment was conducted under non-saline condition to determine the effect of lupin residue rate (2% and 4% w/w) on wheat growth. The second experiment was conducted under saline conditions to determine the effect of P added as lupin residue (2%) and/or KH2PO4 (0, 20 and 40 mg P kg-1 soil) with and without 50 mg N kg-1 soil added as (NH4)2.SO4 on microbial biomass, N and P availability, plant growth and nutrient composition in the saline sandy loam soil. The EC1:5 were 0.23, 0.35 and 0.51 dS m-1, equivalent to ECe 3.1, 4.8 and 7.0 dS m-1, respectively. In the first experiment under non-saline conditions, shoot dry weight was lower with addition of 4% than with 2% lupin residue with and without inorganic N. In the second experiment under saline conditions, microbial biomass C and N increased with increasing application of inorganic P, but was not as much as in presence of lupin residues. In presence of lupin residue, wheat growth increased with increasing addition of inorganic P under saline conditions. Compared to the soil with P from inorganic fertilizer and residues, inorganic P increased shoot and root dry weights and shoot P, K, Mn and Zn concentrations, but not N concentration. Addition of 50 mg inorganic N in presence of lupin residues significantly increased N and P availability and microbial biomass, but had no significant effect on wheat growth in a saline sandy loam soil. The results showed that optimal application of N and P organic and inorganic fertilizers can improve N and P availability, microbial activity and wheat growth in salt affected soils. Highest wheat dry weight was achieved by application of 60 mg P kg-1 soil in a sandy loam soil with EC1:5 0.67 dS m-1, equivalent to ECe 9.2 dS m-1. Wheat growth was also improved with application of N-NH4 + or as NH4NO3 at 100 mg N kg-1 soil. These N and P fertilization rates can potentially enhance wheat growth in the sandy loam soil with up to EC1:5 0.67 dS m-1, but with SAR 1 at neutral pH. Plant residues increased microbial activity and N and P availability in the saline soils. In the soils used here, with residue addition wheat growth was P limited due to competition with microorganisms for available P. Therefore application of residues with inorganic P is necessary to satisfy wheat requirements of N and P in the saline sandy loam soil. In the saline sandy loam soil at SAR 1 and neutral pH, application of 2% lupin residues and 40 mg KH2PO4-P kg-1 soil achieved highest microbial biomass, nutrient availability and wheat growth. However, wheat growth with these rates is not as high as with inorganic P at similar rate due to micronutrient deficiency in the saline soil with lupin residues. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1331419 / Thesis (Ph.D.) -- University of Adelaide, School of Earth and Environmental Sciences, 2008

Thesis (M.S.)--Oregon State University, 2008. / Printout. Includes bibliographical references (leaves 159-167). Also available on the World Wide Web.

Fertility-building crops (FBCs) offer the opportunity to alleviate the costs of inorganic fertiliser by providing an alternative supply of available nitrogen (N) in soils. A survey of relevant literature reviewed the types of FBCs, their nitrogen accumulation potentials, residue characteristics, and subsequent release patterns. It also identified a paucity of data concerning the response of different species to UK climatic, soil, and management conditions. In order to investigate these relationships further pot and field trials were established in 2007 at the Royal Agricultural College, Cirencester (SP 00481 01382) and at Coates Manor Farm (SO 98473 00402) on Sherborne series (typical Cotswold) soils, to investigate the biology and morphology of FBCs potentially suitable for short term fertility-building, their accumulation of N under field conditions, and its subsequent recovery within test crops. Data so obtained was used as a verification and refinement tool for the FBC model (Cuttle et al, 2003), a simple, commercially applicable, rotation-based model which can be applied to both organic and conventional production systems. Nine leguminous and two non-leguminous FBC treatments were established in April 2007 by straight sowing, followed by mulching at the conclusion of the nitrogen accumulation phase and by undersowing in spring barley (Hordeum sativum). The recovery test crops (winter and spring wheat Triticum aestivum L.) were established in September 2007 and March 2008. All FBCs established successfully. Above-ground dry matter (DM) yield and residue quality (C:N ratio) of FBCs varied significantly (P<0.05) between crops and cropping regimes with a significant correlation (r2=0.418) between DM yields and C:N ratios. FBCs and cropping regimes had significant effects (P<0.001 and P<0.05 respectively) on potential mineralisable nitrogen (PMN) levels in the soil and on the grain yields of winter and spring wheat test crops. Straight sown Lupinus albus, Trifolium pratense, Trifolium repens and a legume mixture resulted in higher winter wheat grain yields. However, the opportunity cost associated with straight sowing (i.e. the gross margin foregone from a spring barley crop) meant that the rotation would probably not be viable economically. Undersown Medicago lupulina, Vicia villosa, T. pratense, T. repens and the legume mixture gave worthwhile yield increases in spring wheat without incurring a yield penalty in the spring barley cover crop. Following enhancement and using actual data from the trials, the FBC model (Cuttle et al, 2003) provided encouraging predictions (R>0.6) for soil mineral nitrogen (SMN) and key parameters were identified for future use. It was concluded that FBCs established for short term soil fertility building could provide a worthwhile enhancement of soil N levels and grain yields in a conventional arable rotation, particularly in spring wheat following FBCs undersown in spring barley. It was also concluded that the FBC model (Cuttle et al, 2003), following further enhancement, and using additional data from these and other similar trials, could provide reasonably accurate estimates of SMN to aid more precise applications of N fertiliser in the future.

The environmental impact of anthropogenic disturbances such as agriculture, on the soil ecosystem, and particularly on soil microbial structural and functional diversity, is of great importance to soil health, conservation and remediation. Therefore, this study assessed the effects of various land use and management practices on both the structural (genetic) and functional (catabolic) diversity of the soil bacterial and fungal communities, at two long-term sites in KwaZulu-Natal. The first site is situated at Baynesfield Estate, and the second at Mount Edgecombe Sugarcane Research Institute. At site 1, the land uses investigated included soils under pre-harvest burnt sugarcane (Saccharum officinarum, Linn.) (SC); maize (Zea mays, Linn.) under conventional tillage (M); permanent kikuyu (Pennisetum clandestinum, Chiov) pasture (KIK); pine (Pinus patula, Schiede) plantation (PF); and wattle (Acacia mearnsii, De Wild) plantation (W), all fertilized; and undisturbed native grassland (NAT) that had never been cultivated or fertilized. At site 2, a sugarcane (Saccharum officinarum × S. spontaneum var. N27) pre-harvest burning and crop residue retention trial was investigated. The treatments studied included conventional pre-harvest burning of sugarcane with the tops removed (Bto), and green cane harvesting with retention of crop residues on the soil surface as a trash blanket (T). Each of these treatments was either fertilized (F) or unfertilized (Fo). The polymerase chain reaction (PCR), followed by denaturing gradient gel electrophoresis (DGGE) were used to determine the structural diversity, and community level physiological profiling (CLPP) using BIOLOG plates, the catabolic diversity. In addition, the soils were analysed with respect to selected physicochemical variables, and the effects of these on the soil microbial communities were determined. Replicate soil samples (0–5 cm) were randomly collected from three independent locations within each land use and management, at both sites. Soil suspensions for the CLPP analyses were prepared from fresh soil subsamples (within 24 h of collection) for the bacterial community analyses, and from 8-day-old soil subsamples (incubated at 4°C to allow for spore germination) for the fungal community analyses. BIOLOG EcoPlates™ were used for the bacterial CLPP study and SF-N2 MicroPlates™ for the fungal analysis, the protocols being adapted and optimized for local conditions. This data was log [X+1]-transformed and analysed by principal component analysis (PCA) and redundancy analysis (RDA). For PCRDGGE, total genomic DNA was isolated directly from each soil subsample, and purified using the MO BIO UltraClean™ soil DNA Isolation kit. Protocols were developed and optimized, and fragments of 16S rDNA from soil bacterial communities were PCR-amplified, using the universal bacterial primer pair 341fGC/534r. Different size 18S rDNA sequences were amplified from soil fungal communities, using the universal fungus-specific primer pairs NS1/FR1GC and FF390/FR1GC. Amplicons from both the bacterial and fungal communities were fingerprinted by DGGE, and bands in the fungal DGGE gels were excised and sequenced. The DGGE profiles were analysed by Bio-Rad Quantity One™ Image analysis software, with respect to band number, position, and relative intensity. Statistical analyses of this data then followed. Soil properties [organic C; pH (KCl); exchangeable acidity; total cations (ECEC); exchangeable K, Ca and Mg; and extractable P] were determined by PCA and were shown to have affected the structural and catabolic diversity of the resident microbial communities. At Baynesfield, canonical correspondence analysis (CCA) relating the selected soil variables to bacterial community structural diversity, indicated that ECEC, K, P and acidity were correlated with CCA1, accounting for 33.3% of the variance, whereas Mg and organic C were correlated with CCA2 and accounted for 22.9% of the variance. In the fungal structural diversity study, pH was correlated with CCA1, accounting for 43.8% of the variance, whereas P, ECEC and organic C were correlated with CCA2, and accounted for 30.4% of the variance. The RDA of the catabolic diversity data showed that the same soil variables affecting fungal structural diversity (organic C, P, ECEC and pH) had influenced both the bacterial and fungal catabolic diversity. In both the bacterial and fungal RDAs, organic C, P and ECEC were aligned with RDA1, and pH with RDA2. However in the bacterial analysis, RDA1 accounted for 46.0%, and RDA2 for 27.5% of the variance, whereas in the fungal RDA, RDA1 accounted for only 21.7%, and RDA2 for only 15.0% of the variance. The higher extractable P and exchangeable K concentrations under SC and M, were important in differentiating the structural diversity of these soil bacterial and fungal communities from those under the other land uses. High P concentrations under M were also associated with bacterial catabolic diversity and to a lesser extent with that of the soil fungal communities under M. Similarly, the higher organic C and exchangeable Mg concentrations under KIK and NAT, possibly contributed to the differentiation of these soil bacterial and fungal communities from those under the other land uses, whereas under PF, the high exchangeable acidity and low pH were possibly influencing factors. Under W, low concentrations of P and K were noted. Other factors, such as the presence/absence and frequency of tillage and irrigation, and the diversity of organic inputs due to the diversity of the above-ground plant community, (in NAT, for example) were considered potentially important influences on the nature and diversity of the various land use bacterial and fungal communities. At Mount Edgecombe, CCA showed that organic C and Mg had a significant effect on soil bacterial structural diversity. Organic C was closely correlated with CCA1, accounting for 58.7% of the variance, whereas Mg was associated with CCA2, and accounted for 41.3% of the variance. In the fungal structural diversity study, ECEC and pH were strongly correlated with CCA1 and accounted for 49.1% of the variance, while organic C was associated with CCA2, accounting for 29.6% of the variance. In the functional diversity studies, RDA showed that both bacterial and fungal community catabolic diversity was influenced by soil organic C, pH, and ECEC. In the bacterial analysis, RDA1 was associated with organic C and pH, and accounted for 43.1% of the variance, whereas ECEC was correlated with RDA2, accounting for 36.9% of the variance. In the fungal analysis, RDA1 was correlated with ECEC and accounted for 47.1% of the variance, while RDA2 was associated with pH and organic C, accounting for 35.8% of the variance. The retention of sugarcane harvest residues on the soil surface in the trashed treatments caused an accumulation of organic matter in the surface soil, which did not occur in the pre-harvest burnt sugarcane. This difference in organic C content was a factor in differentiating both bacterial and fungal communities between the trashed and the burnt treatments. Soil acidification under long-term N fertilizer applications caused an increase in exchangeable acidity and a loss of exchangeable Mg and Ca. Thus, as shown by CCA, a considerably lower exchangeable Mg concentration under F compared to Fo plots resulted, which was influential in differentiating the bacterial and fungal communities under these two treatments. In the structural diversity study at Baynesfield, differences were found in bacterial community species richness and diversity but not in evenness, whereas in the fungal analysis, differences in community species richness, evenness and diversity were shown. The soil bacterial and fungal communities associated with each land use were clearly differentiated. Trends for bacterial and fungal diversity followed the same order, namely: M < SC < KIK < NAT < PF < W. At Mount Edgecombe, no significant difference (p > 0.05) in bacterial structural diversity was found with oneway analysis of variance (ANOVA), but two-way ANOVA showed a slight significant difference in bacterial community species richness (p = 0.05), as an effect of fertilizer applications. A significant difference in fungal species richness (p = 0.02) as a result of management effects was detected, with the highest values recorded for the burnt/fertilized plots and the lowest for the burnt/unfertilized treatments. No significant difference was shown in species evenness, or diversity (p > 0.05), in either the bacterial or the fungal communities. In the catabolic diversity study at site 1, the non-parametric Kruskal-Wallis ANOVA showed that land use had not affected bacterial catabolic richness, evenness, or diversity. In contrast, while fungal catabolic richness had not been affected by land use, the soil fungal community catabolic evenness and diversity had. At site 2, the land treatments had a significant effect on soil bacterial community catabolic richness (p = 0.046), but not on evenness (p = 0.74) or diversity (p = 0.135). In the fungal study, land management had no significant effect on the catabolic richness (p = 0.706), evenness (p = 0.536) or diversity (p = 0.826). It was concluded, that the microbial communities under the different land use and trash management regimes had been successfully differentiated, using the optimized protocols for the PCR-DGGE of 16S rDNA (bacteria) and 18S rDNA (fungi). Sequencing bands produced in the 18S rDNA DGGE, enabled some of the soil fungal communities to be identified. CLPP of the soil microbial communities using BIOLOG plates showed that, on the basis of C substrate utilization, the soil bacterial and fungal communities’ catabolic profiles differed markedly. Thus, it was shown that the different land use and management practices had indeed influenced the structural and catabolic diversity of both the bacterial and fungal populations in the soil. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2011.

Thesis (Ph.D.)--University of Western Australia, 2006.

Dryland salinity is a major and expanding threat to agricultural land in Australia. Animal production from forages grown on saline land is perhaps its most promising economic use. Glycophytic forage legumes have been evaluated under saline conditions mainly for agronomic characteristics and, to a lesser extent, for nutritive quality to animals. Plant growth and its nutritive quality are interrelated, but a decline in yield in response to salinity may be associated with effects on the chemical constituents of the plant since soil salinity affects plant metabolism. This research aimed to investigate changes in the components of yield and nutritive value of two legumes species. Lucerne ( Medicago sativa ) and Melilotus ( Melilotus albus ) were exposed to different levels of NaCl in the range of 0 to 110 mM NaCl. The research tested the hypothesis that the components of plant nutritive value are not as sensitive to salinity as shoot biomass production since the adaptive mechanisms of the plant lessen harmful effects of the salts. For both plant species, salinity decreased leaf and stem dry matter production, but increased leaf - to - stem ratio. In addition, salinity resulted in earlier flowering in Melilotus. Mineral composition was the most sensitive component of forage quality. Calculated sodium chloride concentrations were up to 125 g / kg DM in lucerne and 39 g / kg DM in Melilotus when irrigated with 110 mM NaCl. The concentrations of calcium and magnesium decreased in both species and approached the marginal range for animal production. Zinc concentration also decreased while potassium decreased in stems of lucerne only. The digestible organic matter ( DOMD ) in response to salinity varied between species. At the highest salt concentration, the whole shoot ( i.e., leaf and stem ) of lucerne decreased up to 4 percentage units while Melilotus increased by 6 percentage units. In lucerne, DOMD was influenced by a high concentration of soluble ash in leaf and stem and, in Melilotus, by an increase in the organic matter content of leaf and a reduction in lignin concentration in stem, which favoured higher digestibility. These results were supported by a histological study in which an increase in starch in Melilotus leaf, and a lower proportion of xylem in relation to parenchyma in stems, was measured. Crude protein concentration was not compromised and, in relation to Melilotus, coumarin concentration did not increase with salinity. In conclusion, the reduction in DM production of species with similar salt tolerance does not necessarily correspond to an equivalent reduction in nutritive value. This research represents the most detailed study into effects of salinity on glycophytic forage legumes. Results show that while some aspects of forage quality ( e.g., minerals composition and energy ) are strongly influenced by salinity, other aspects ( e.g., protein ) remain relatively unaffected. These findings have implications for development of productive grazing systems on saline agricultural land. / Thesis (Ph.D.)--School of Agriculture, Food and Wine, 2006.

Dryland salinity is a major and expanding threat to agricultural land in Australia. Animal production from forages grown on saline land is perhaps its most promising economic use. Glycophytic forage legumes have been evaluated under saline conditions mainly for agronomic characteristics and, to a lesser extent, for nutritive quality to animals. Plant growth and its nutritive quality are interrelated, but a decline in yield in response to salinity may be associated with effects on the chemical constituents of the plant since soil salinity affects plant metabolism. This research aimed to investigate changes in the components of yield and nutritive value of two legumes species. Lucerne ( Medicago sativa ) and Melilotus ( Melilotus albus ) were exposed to different levels of NaCl in the range of 0 to 110 mM NaCl. The research tested the hypothesis that the components of plant nutritive value are not as sensitive to salinity as shoot biomass production since the adaptive mechanisms of the plant lessen harmful effects of the salts. For both plant species, salinity decreased leaf and stem dry matter production, but increased leaf - to - stem ratio. In addition, salinity resulted in earlier flowering in Melilotus. Mineral composition was the most sensitive component of forage quality. Calculated sodium chloride concentrations were up to 125 g / kg DM in lucerne and 39 g / kg DM in Melilotus when irrigated with 110 mM NaCl. The concentrations of calcium and magnesium decreased in both species and approached the marginal range for animal production. Zinc concentration also decreased while potassium decreased in stems of lucerne only. The digestible organic matter ( DOMD ) in response to salinity varied between species. At the highest salt concentration, the whole shoot ( i.e., leaf and stem ) of lucerne decreased up to 4 percentage units while Melilotus increased by 6 percentage units. In lucerne, DOMD was influenced by a high concentration of soluble ash in leaf and stem and, in Melilotus, by an increase in the organic matter content of leaf and a reduction in lignin concentration in stem, which favoured higher digestibility. These results were supported by a histological study in which an increase in starch in Melilotus leaf, and a lower proportion of xylem in relation to parenchyma in stems, was measured. Crude protein concentration was not compromised and, in relation to Melilotus, coumarin concentration did not increase with salinity. In conclusion, the reduction in DM production of species with similar salt tolerance does not necessarily correspond to an equivalent reduction in nutritive value. This research represents the most detailed study into effects of salinity on glycophytic forage legumes. Results show that while some aspects of forage quality ( e.g., minerals composition and energy ) are strongly influenced by salinity, other aspects ( e.g., protein ) remain relatively unaffected. These findings have implications for development of productive grazing systems on saline agricultural land. / Thesis (Ph.D.)--School of Agriculture, Food and Wine, 2006.

Submitted by Claudia Rocha (claudia.rocha@udesc.br) on 2018-03-05T15:11:45Z No. of bitstreams: 1 PGCS15MA133.pdf: 896441 bytes, checksum: ec545b22c2ffa4326a04252cacd54157 (MD5) / Made available in DSpace on 2018-03-05T15:11:45Z (GMT). No. of bitstreams: 1 PGCS15MA133.pdf: 896441 bytes, checksum: ec545b22c2ffa4326a04252cacd54157 (MD5) Previous issue date: 2015-10-22 / CNPq / Different soil management systems may cause chemical, physical and biological changes in the soil. The objective of this research was to evaluate chemical and physical soil attributes in an experiment involving crops rotations and no-tillage system for onion productions and its relationship with bulbs production. This experiment was conducted at an Experimental Station belonging to EPAGRI and located in Ituporanga, SC in a Humic Dystrophic Cambisol, 8 years after the implantation of the no-tillage system and crops rotation for onion, the treatments evaluated were: T1: maize-onion (succession), T2: commercial rotation-biennial onion, T3: maize-biennial onion, T4:maize-velvet-onion, T5: soil coverage grass–annual onion, T6: legumes coverage-annual onion, conventional tillage system (CTS): coverage crops rotation-annual onion and T8: coverage crops consortium-annual onion. The soil samples for the analysis were collected at the layers of 0-5, 5-10 and 10-20 cm. The physical attributes evaluated were: stability of soil aggregates, total porosity, macroporosity, microporosity, bulk density, clays flocculation degree, saturated hydraulic conductivity, resistance to soil penetration and the chemical attributes were: total organic carbon, particulate carbon, carbon associated to minerals, total nitrogen, phosphorus, potassium, magnesium, calcium, aluminium, pH-H2O and pH-CaCl2, potential acidity. The treatments had different effects on the physical attributes, the increase of the resistance to soil penetration and bulk density reduced the macroporosity and the total porosity, at the layer of 0-5 cm, the conventional tillage system had lower aggregate stability than the no-tillage system. The concentrations of Ca, Mg, K, total organic carbon and carbon associated to minerals were similar in all the treatments. The no-tillage system when associated to crops rotations may improve the soil structure and increase the total organic carbon at the layer of 0-5 cm. The treatment T6 presented the highest yield of onion and PC the lowest / Diferentes sistemas de manejo do solo podem causar alterações químicas, físicas e biológicas do solo. O objetivo desta pesquisa foi avaliar atributos físicos e químicos do solo em um experimento envolvendo rotação de culturas e plantio direto de cebola e sua relação com a produtividade de bulbos. Este experimento foi conduzido na Estação Experimental da Epagri em Ituporanga, SC, em Cambissolo Húmico Distrófico, após 8 anos da implantação do sistema de plantio direto e rotação de culturas para a cebola. Os tratamentos foram: T1: sucessão milho-cebola, T2: rotação comercial-cebola bienal, T3: milho-cebola bienal, T4: milho-mucuna-cebola bienal, T5: gramíneas de cobertura-cebola anual, T6: leguminosas de cobertura-cebola anual, PC (preparo convencional): rotação de coberturas e cebola anual e T8: consórcio de coberturas-cebola anual. As amostras para o estudo foram coletadas nas camadas de 0-5, 5-10 e 10-20 cm. Os atributos físicos avaliados foram: resistência a penetração, densidade do solo, porosidade total, macroporosidade, microporosidade, grau de floculação, condutividade hidráulica saturada, estabilidade de agregados e os atributos químicos foram: Ca, Mg, K, P, N, Al trocável, acidez potencial, pH-H2O, pH-CaCl2, carbono orgânico total (COt), carbono orgânico particulado (COp), carbono orgânico associado aos minerais (COam). A estabilidade de agregados na camada de 0-5 cm foi menor no sistema convencional em relação aos sistemas conservacionistas. Para os atributos químicos do solo, os teores de Ca, Mg, K, COt e COam foram semelhantes em todas as camadas avaliadas. O sistema plantio direto quando associado a rotação de culturas pode contribuir para a melhoria da estrutura do solo e manutenção dos teores de matéria orgânica na camada superficial do solo