In Europe the views on the demand of magnesium by agricultural plants as well as on the need for magnesium fertilization are different. In European countries uses different methods for determining the available magnesium content in soil. Different assessment of soil characteristics in different countries as well as very unequal magnesium fertilization rates for crops have encouraged us to review the methods of determining available magnesium in soil and the effect of magnesium fertilizer on plants. The appropriateness of applying the magnesium determination methods commonly used in different soils in Europe was established and scientifically based as well as their relationship, recalculation algorithms for the values of available magnesium obtained by applying different determination methods were prepared. The effect of the plant available magnesium content in predominant soils of Lithuania determined by different methods and that of magnesium fertilizer on the yield of Italian ryegrass and spring barley were investigated. Summarizing the research developed the most suitable determination of available magnesium in Lithuanian soil and crop fertilization magnesium fertilizer recommendations. Different solubility of magnesium in different soils and magnesium fertilizers on agricultural plants in Lithuania was studied for the first time. / Požiūris į magnio poreikį žemės ūkio augalams, o tuo pačiu tręšimą magnio trąšomis, įvairiose šalyse nėra vienodas. Europos šalyse judrusis magnis dirvožemyje nustatomas labai įvairiais metodais. Skirtingas dirvožemio savybių vertinimas įvairiose šalyse, o taip pat labai nevienodos magnio trąšų normos augalams mus paskatino naujai peržiūrėti judriojo magnio nustatymo metodus dirvožemyje ir magnio trąšų įtaką augalams. Nustatytas ir moksliškai įvertintas dažniausiai Europoje naudojamų judriojo magnio nustatymo metodų taikymo tinkamumas įvairiuose dirvožemiuose, jų tarpusavio priklausomumas, parengti perskaičiavimo algoritmai tarp įvairiais metodais nustatytų judriojo magnio reikšmių. Vyraujančiuose Lietuvos dirvožemiuose ištirta įvairiais metodais nustatyto judriojo magnio kiekio ir magnio trąšų įtaka gausiažiedžių svidrių bei vasarinių miežių derliui ir kokybei. Apibendrinus atliktus tyrimus parengtos tinkamiausių judriojo magnio nustatymo Lietuvos dirvožemiuose metodų ir žemės ūkio augalų tręšimo magnio trąšomis rekomendacijos. Lietuvoje įvairaus tirpumo magnio kiekiai įvairiuose dirvožemiuose ir magnio trąšų įtaka žemės ūkio augalams tirta pirmą kartą.

In Limpopo Province of South Africa, poor soil fertility and low crop yields are serious problems facing resource poor smallholder farmers. A survey of over 60 farmers in 2 villages (Gabaza and GaKgoroshi) found that most of the smallholder farmers were women (68%), elderly (50% above 68 years of age) and had not attended school or only attended up to the primary level (80%). Very few farmers kept livestock (usually in small numbers) and most grew cereal and legume crops (on 1ha of land) for home consumption and livestock feed, with legumes being planted on 13% of the land. The study showed that 80% of farmers were not fully aware of the benefits of legumes in fixing nitrogen (N) and improving yield. A field study at the survey village of Gabaza found that the application of fertiliser N and grass mulch combination and fertiliser N plus guarbean mulch significantly increased plant height and maize shoot growth at 4 and 8 weeks after planting. However, when grass mulch was without N fertiliser, there was no increase in maize growth relative to the control (0N). A farming systems simulation model (Agricultural Production Systems sIMulator - APSIM) was used to simulate this field study as well as over the long-term (1971 to 2008). Simulation analysis showed poor average maize yield (<3000 kg ha⁻ ¹) with the application of grass residues even when used with 30 kg N fertiliser. However, the application of guarbean residues as mulch with or without N fertiliser and as green manure increased maize yields to >4000 kg ha⁻ ¹. Simulation showed that the grass mulch with or without the addition of N fertiliser reduced water stress and soil water evaporation but increased N stress during the reproductive phase of the crop in most seasons. When guarbean mulch was used as green manure by itself, or mulch plus N fertiliser, N stress was reduced but water stress and soil water evaporation were increased which could have been due to faster decomposition of legume mulch as compared to grass mulch. Addition of N fertiliser reduced N stress to maize but increased water stress and soil water evaporation similar to the guarbean mulch because of high soil evaporation. APSIM analysis clearly showed the importance of N x soil water interactions in determining maize growth and yield at Gabaza. Therefore, two studies were undertaken in the laboratory in Australia to determine the dynamics of carbon (C) and N where residues of different qualities [canola (C:N 43), wheat (26), pea (9) and mucuna (14)] were applied to clay loam (Tarlee) or sandy (Waikerie) soils. In experiment 1, where residues were incorporated into the two soils, the cumulative CO₂-C evolution for the wheat and canola treatments at the end of the incubation period were fairly similar but significantly higher than for pea, mucuna and the control. In general, the application of residues increased microbial biomass C more than the control, with highest increases up to 1.48 and 1.56 mg C g⁻ ¹ soil for canola and wheat in Tarlee soil, respectively and 0.82 mg C g⁻ ¹ soil for pea in Waikerie soil. Even though the Tarlee soil showed greater C release than Waikerie soil, the C turnover from the residues between the 2 soils was not significantly different except for pea residues. Canola and wheat residues were found to immobilise N whereas N content increased in both soils with the application of legumes (pea and mucuna). In experiment 2, mucuna, pea and wheat residues were either incorporated or applied as surface mulches on Waikerie soil. Initially the CO₂-C release was higher for incorporated than mulched residues and CO₂-C released was higher for pea residues. However, at the end of the incubation more CO₂-C was released with the application of wheat residue indicating differences between residue types in the pattern of soil respiration. Microbial biomass C was higher for incorporated than mulched residue treatments; pea residue showed the highest biomass C for incorporated (0.78 mg C g⁻ ¹ soil) whereas mucuna had the highest microbial biomass (0.11 mg C g⁻ ¹ soil) treatments. The method of residue application resulted in a significant difference in C turnover between residues, with pea residue showing significant increase in C utilisation than mucuna and wheat. The pea residues, which had the lowest C:N, increased soil mineral N more than other treatments in both incorporated and mulched treatments. Lower mineralisation of N observed in residues of high C:N ratio compared to the control could be due to immobilisation of N. Therefore, understanding the nutrient dynamics of different crop residues could play an important role in the management of residues in different soil types. Based on these results it can be concluded that legume residues have the potential to improve soil fertility and crop yields in dryland farmers’ fields in Limpopo. Extension programs aimed at increasing farmers’ knowledge of the benefits of N fixation by legumes may increase their adoption and thereby improve soil fertility and maize yield. / Thesis (M.Ag.Sc.) -- University of Adelaide, School of Agriculture, Food and Wine, 2010

Surges of Sargassum have become more severe and at the time of writing the largest surge yet is set to hit the Caribbean islands, affecting tourism and marine life negatively. Tourism is Grenada’s single handedly largest economic sector, which is why it is important to research the use of Sargassum. Furthermore, for its fertiliser needs, Grenada relies largely on importing inorganic fertiliser, which has become more expensive in recent years. Sargassum as feedstock for biogas digesters and utilising the digestate as fertiliser could be a viable option, but challenges include high heavy metal content and low concentration of nutrients compared to inorganic fertiliser. The aim of this project is to examine heavy metals contents in digestate derived from Sargassum and gaining knowledge about the current agricultural situation, with regards to fertiliser, through interviewing farmers and relevant political figures. The results from the heavy metal analysis of the liquid digestate showed that the concentration of both arsenic and cadmium were below the average for commercial organic fertilisers. However, further testing is considered to be required to conclude whether the product is suitable to use. Gathered from the interviews was that many farmers were concerned about the impact inorganic fertiliser had on the land, however, the choice of fertiliser was, in general heavily dependent on which type was available. Sargassum-based digestate could be viable on the island but challenges of reducing, transporting and separating heavy metals from the digestate have to be solved making it difficult for the Sargassum to be cost-effective. Furthermore, the farmers were very clear that they wanted a product which was safe to use. / Sargassumblomningar har blivit allvarligare och i skrivande stund väntas den största vågen hittills att drabba de karibiska öarna, vilket har en negativ påverkan på turismen och det marina livet. Turismen är Grenadas enskilt största ekonomiska sektor, och därför är det viktigt att undersöka användningsområdet för Sargassum. Dessutom är Grenada, för sitt gödselbehov, till stor del beroende av import av oorganiskt gödningsmedel, vilket har ökat i pris de senaste åren. Sargassum som inmatning för biogasrötningsanläggningar och användning av rötrester som gödningsmedel skulle kunna vara ett lönsamt alternativ, men utmaningarna är bland annat det höga innehållet av tungmetaller och den låga koncentrationen av näringsämnen jämfört med oorganiska gödningsmedel. Syftet med detta projekt är att undersöka innehållet av tungmetaller i digestat från Sargassum och att få kunskap om den nuvarande jordbrukssituationen gällande gödningsmedel genom att intervjua jordbrukare och relevanta politiker. Resultatet av den tungmetallanalys som genomfördes av det vätskeformiga digestatet visade ett innehåll av kadmium och arsenik som låg under medelvärdet för kommersiella organiska gödningsmedel. Däremot är vidare testning är nödvändig för att säkerställa att produkten är lämplig att använda. Intervjustudien visade att många jordbrukare var oroade över hur oorganiska gödselmedel påverkar marken, men att valet av gödselmedel i allmänhet var starkt beroende av vilken typ av gödningsmedel som fanns tillgängligt. Sargassumbaserat digestat skulle kunna vara lönsamt för användning på ön, men problemen med reducering, transport och separering av tungmetaller från digestatet måste lösas, vilket gör det svårt för Sargassum att vara kostnadseffektivt. Bönderna var slutligen tydliga med att digestatet från Sargassum behövde generera en ökning eller likvärdig produktion av deras grödor.

Thesis (MSc. Agriculture(Soil Science) -- University of Limpopo, 2018 / Soil acidity is one of the abiotic stress factors that greatly limit the productivity of crops on farmers’ fields. A greenhouse study was carried out over two summer growing seasons to evaluate the effect of lime and phosphorus (P) application rates on the growth, yield and root attributes of a determinate cowpea variety on acid soil. The experiment was laid out as a 4x5 factorial arrangement with 4 replications. Treatment factors comprised of variable rates of Vaalburg dolomitic lime (0, 2, 4 and 6 t ha-1) and P (0, 15, 30, 45 and 60 kg ha-1) using single super phosphate, 10.5% P. The two treatment factors were combined resulting in a total of 20 treatment combinations. Data collected included cowpea growth parameters, crop phenology, yield attributes and root characteristics. While cowpea plants with no P application consistently gave the least plant height, stem diameter, number and length of trifoliate leaves, the 6 t ha1 lime rate appears to be completely disadvantaged for all measured parameters with generally lower values than in soil filled pots without lime application. Results showed that soil pH was increased with 6 t ha-1 lime application while soil electrical conductivity (EC), percent of organic matter (OM) and total organic carbon (TOC) were all increased with increasing P and lime rates. All measured cowpea growth attributes such as plant height, stem diameter, number of trifoliate leaves, and leaf area were significantly increased (p≤0.05) with increasing P and lime rates. During the two planting seasons, P and lime application resulted in reduced (p≤0.05) duration to flowering, pod formation and physiological maturity. The 6 t ha-1 lime application produced higher number of pods (2.50) compared to the other rates. Application rates of 45 kg P ha-1 and 6 t ha-1 of lime produced superior number of seeds per pod with high values of (13.71) and (12.85), respectively. However, cowpea root attributes namely number of nodules per plant, the third branching root diameter, angle of adventitious root, tap root diameter at 5 and 10 cm, shallow and deep score were significantly increased at moderate P rate of 30 kg P ha-1. Overall, findings of this study revealed that application of both P fertiliser and lime were able to ameliorate the negative effect of P deficiency from soil acidity on the evaluated cowpea variety and promoted increased yield. Keywords: Acid soil, grain cowpea, P fertiliser, lime, growth, root characteristics, yield / National Research Foundation (NRF) and Department of Agriculture, Forestry and Fisheries (DAFF)

In Mediterranean-type climates, topsoil frequently dries out during spring. Problems associated with reduced nutrient (P, K) availability in dry topsoil may be overcome by placing fertilisers deeper in the soil, where the soil is more likely to remain moist for longer periods as opposed to conventional fertiliser placement. Deep-P placement has resulted in significant yield improvements for lupin crops in Mediterranean environments because lupin crops generally require soil P supply during spring (throughout the flowering stage); in contrast, wheat yields have seldom improved with deep P placement, presumably because plants have accumulated sufficient P prior to spring (grain filling stage) for maximum grain yields. The P and K accumulation patterns of canola had not been investigated, and therefore any potential yield benefits of deep placed fertilisers were unknown. This study aimed to define the P and K demands of canola throughout the growing season, and assess the viability of deep placement of fertiliser in matching soil P and K supply to crop demand. The study further investigated the impact of deep placement of P fertiliser on root growth and distribution throughout the soil profile. Initial glasshouse studies compared the P and K accumulation patterns of several canola cultivars with wheat, and found that the P and K demand of canola continued until later into the season than wheat, but there was little difference in the P and K accumulation patterns of the various canola cultivars. Further experiments in sand culture determined that regardless of the level of K supply, canola plants had accumulated sufficient K for maximum seed yields by early flowering. Under high P supply, canola plants had accumulated enough P for maximum seed yields by early flowering, but when P supply during vegetative growth was just adequate, plants required a continual P supply until mid silique-filling to attain maximum yields. Because plants had accumulated sufficient K for maximum seed yields by early flowering (therefore topsoil drying in spring was unlikely to affect yields), further field experiments examined only deep placement of P fertiliser to improve P uptake and yields.

The current silvicultural regimes of Pinus radiata plantations in New Zealand with wider initial tree spacings have created the potential for increased growth of understorey vegetation. A consequence of this is that the response of P. radiata to P fertiliser is expected to be more influenced by the interaction between the P fertiliser, the tree and the understorey vegetation than was the case in the past. The objectives of this study were to investigate the influence of different rates of a soluble and a sparingly-soluble P fertiliser (Triple superphosphate and Ben-Geurier phosphate rock) and weed control, and their interactions, on soil P chemistry and the growth and P uptake of 4-5-year-old second-rotation P. radiata on an Allophanic Soil (Kaweka forest) and a Pumice Soil (Kinleith forest). The results showed that the application of P fertilisers had no effect on P. radiata growth at both field trial sites two years after this treatment, although it increased radiata needle P concentration. However, at both sites, the understorey vegetation removal treatment increased tree diameter at breast height and basal area. At the highly P-deficient (Bray-2 P 4 µg g-1) Kaweka forest, the presence of understorey (bracken fern and some manuka) reduced resin-Pi and Olsen P concentrations, but at the moderate P fertility (Bray-2 P 13 µg g-1) Kinleith forest, the understorey (Himalayan honeysuckle, buddleia and some toetoe) increased Bray-2 P, resin-Pi, and Olsen P concentrations. A glasshouse study on P. radiata seedlings was conducted to test the hypothesis that when ryegrass (Lolium multiflorum) is grown with P. radiata, it increases radiata needle P concentration, while when broom (Cytisus scoparius L.) is grown with P. radiata, it has no effect. The acid phosphatase activity in the rhizosphere of P. radiata was higher when radiata was grown with broom than that when it was grown with ryegrass. This is consistent with the higher P concentration in needles of radiata grown with broom than that of radiata grown with ryegrass, in the absence of P fertiliser addition. However, when P fertiliser was added (50 and 100 µg P g-1 soil) the needle P concentration of radiata grown with broom was lower than that when radiata was grown with ryegrass.

Nutrients for plant growth are often limited in soil systems and additions are required in the form of fertiliser. Potassium is an essential macro-nutrient for plants and demands for K are expected to increase in the future. Glaucony is an abundant marine mineral which may provide an alternative K-rich fertiliser resource. The South Island of New Zealand contains deposits of glaucony-rich rocks which were deposited in the Early- to Mid-Cenozoic during periods of low sedimentation to the seafloor. Here, the geochemistry of glaucony from the Waitaki Basin (Otago), the Waipara Greensand (North Canterbury) and the Stoney Creek Limestone (Karamea) was examined using spatially resolved geochemical analysis and dissolution experiments. Grain-by-grain analysis using Laser Ablation Induction Coupled Plasma Mass Spectrscopy (LA-ICP-MS) and Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM + EDS) revealed that glaucony from all deposits were of the mature type and were enriched in K. Glaucony derived from growth inside faecal pellets was found to contain elevated K and Fe concentrations compared to bioclast hosted glaucony. These variations can be explained by the physical properties of host grains and sea-floor redox conditions at the time of precipitation, both of which increased ionic mobility into the zone of glauconitisation. Solubility analysis showed that K^{+} was released from glaucony more rapidly than any other element. Additionally, decreasing the pH and introducing an oxidising agent (i.e, birnessite which is ubiquitous in soil environments) accelerated K^{+} release 13-fold. Trace metals including Cr, Zn, Cu and Ni were present in the solid phase analysis, however further investigation revealed that these elements were released into solution in low concentrations and may present a source of micro-nutrients, not a soil contaminant. These results suggest that glaucony may offer a source of slow releasing K fertiliser, and the South Island of New Zealand is ideally situated as a place to consider using glaucony as a locally sourced, environmentally sustainable K resource for agriculture.

Despite being different cultivars of the same plant species (Zea mays L.), maize and sweet corn have contrasting P fertiliser recommendations in New Zealand, that are reflected in different target Olsen P values of 10-15 mg P/kg soil for optimum maize growth and 26-35 mg P/kg soil for optimum sweet corn growth. Three key hypotheses were developed in this study to explain why these differences may exist: i) maize and sweet corn differ in their responsiveness to P fertiliser i.e. maize is more internally P efficient and requires less P than sweet corn to grow, ii) both cultivars differ in external P efficiency i.e. their ability to take P up from soil iii) both cultivars differ in external P efficiency because they have different root system structure. Two field experiments evaluated the growth and yield responses of maize and sweet to different rates of P fertiliser application. The first experiment was conducted in Hawke's Bay (2001-02) and second in the Manawatu (2002-03) with P application rates of 0, 100 and 200 kg P/ha in the Hawke's Bay and 0, 15 and 70 kg P/ha in the Manawatu. Both experiments were conducted on soils of low available P status. The Olsen P test values of 13 mg P/kg soil in the Hawke's Bay and 11 mg P/kg soil in the Manawatu were far below the recommended values for sweet corn (25-35 mg P/kg soil). In both experiments and across all P treatments maize produced significantly higher dry matter yields than sweet corn during all sampling stages. In the Hawke's Bay experiment at 100 days after sowing (DAS), the maize (87719 plants/ha, 20.9 t/ha) produced 43% more dry matter than sweet corn (71124 plants/ha, 14.6 t/ha), whereas, in the Manawatu experiment (140 DAS), maize (71124 plants/ha, 15.2 t/ha) had a 39% higher dry matter yield than sweet corn (71124 plants/ha, 10.9 t/ha). In both the field experiments, the sweet corn fresh cob yield of 27 and 28 t/ha in the Hawke's Bay and the Manawatu regions and maize grain yields of 16 and 10 t/ha, respectively, were within the range of the reported commercial yields for each region. In both experiments, the P fertiliser application raised the soil P status (Olsen P test values) but caused no significant increases in either maize or sweet corn yields (total dry matter, sweet corn fresh cob or maize grain). Commercially viable yields of both cultivars were able to be achieved without P fertiliser application with Olsen P soil test in the range of 10-15 mg P/kg soil. Sweet corn reached harvestable maturity at 115 DAS in the Hawke's Bay and 140 DAS in the Manawatu experiments. By this time maize had produced 4-6 t/ha more total dry matter yield than sweet corn, yet maize and sweet corn had achieved similar total P uptake (32-37 kg P/ha at 100 DAS in the Hawke's Bay and 18-19 kg P/ha at 140 DAS in the Manawatu). At silking (after 75 DAS in the Hawke's Bay and approximately 110 DAS in the Manawatu), both cultivar's total leaf P concentrations (0.21-0.25%) were within the sufficiency range values for maize crops in New Zealand (0.18-0.33 %). Maize, however was more internally P efficient growing more dry matter per unit P taken up, which was more noticeable in the drier season. Fertiliser P application increased P uptake with both cultivars under moist conditions in the Hawke's Bay experiment (2001-02). However, the dry conditions in the Manawatu (2002-03) limited P uptake as well as restricted dry matter yields with both cultivars. Further, there were no significant differences between maize and sweet corn P uptake efficiency (kg P/kg root) despite significant differences in the root system structure (biomass) for both cultivars at all stages, which lead to different temporal patterns of P uptake. The lack of maize yield response to fertiliser P in both field experiments is consistent with the New Zealand recommendations for growing a maize grain crop (because soil Olsen P was in the range of 10-15 mg P/kg). However, the lack of sweet corn yield response in both field experiments does not support the New Zealand recommendations for growing sweet corn (which assume optimal Olsen P values are 26-35 mg P/kg).

Hedgerows of the fodder tree legume Leucaena leucocephala (Lam.) de Wit ssp. glabrata (Rose Zárate) (leucaena) planted with companion grass (leucaena-grass pasture) form a productive, profitable and sustainable tropical pasture in northern Australia. Leucaena is renowned for its longevity (>30 years) and productivity under regular grazing, and this is a key factor in its profitability. To-date graziers and researchers have not been concerned about the sustainability of commercial leucaena-grass pastures, which are rarely fertilized. However, nutrient depletion could be expected after many years of nutrient removal under heavy grazing without replenishment, even on soils of moderate initial fertility. This study investigated the long-term productivity of leucaena-grass pastures in relation to nutrient depletion in Queensland. Experimental trials were conducted at 3 research stations and 6 commercial cattle properties. Prior to conducting field trials, a postal survey of leucaena growers ascertained perceived changes in leucaena, grass and livestock productivity over time. Physical and management factors influencing long-term pasture productivity were also explored. Graziers reported that leucaena productivity had declined in 58% of aging pastures. Lower livestock productivity was associated with declining leucaena growth, even though grass growth remained vigorous. Leucaena growth decline was more frequent on soil types of marginal initial fertility. Maintenance fertilizer was not applied to most (98%) leucaena pastures surveyed despite significant amounts of nutrient removal, particularly phosphorus (P) and sulphur (S), occurring over prolonged periods of moderate to high grazing pressure. It was predicted that under current management practices large areas of commercial leucaena pasture will be affected by soil nutrient depletion over the next 10 years. The effect of age of leucaena plants on pasture productivity was investigated in pastures aged from 8 to 38 years. Leucaena growth, expressed as rainfall use efficiency (RUE), declined with age (from 4.0 to 1.9 kg total dry matter (DM)/ha/mm), as did leaf nitrogen (N), P and S concentrations. Leucaena productivity decline was attributed to P and S deficiency restricting growth and symbiotic dinitrogen (N2) fixation. Composition of interrow grass changed from native grass dominance before leucaena establishment to green panic (Panicum maximum var. trichoglume) dominance in the aging leucaena pastures, particularly adjacent to leucaena hedgerows. This was attributed to increased soil Navailability. Leucaena and grass roots were concentrated in the topsoil; however, leucaena roots did extend beyond 1 m depth while grass roots did not. Changes in topsoil organic carbon (OC) and total nitrogen (TN) resulting from the planting of leucaena hedgerows into native grass pastures and previously cropped soils were studied. Topsoil OC and TN contents increased significantly under leucaena pasture (OC from 81-290 kg/ha/year and TN from 12-24 kg/ha/yr). Since TN and OC showed similar trends, there was no significant effect on carbon:N ratios. Leucaena contributed to soil OC both directly via plant part decomposition, and indirectly, via enhanced grass growth in the inter-row. Lower topsoil OC accumulation rates (81 kg/ha/yr) were observed in the older leucaena-grass pastures related to the decline in yield and vigour of leucaena in these aging pastures. The amount of carbon dioxide equivalent (CO2-e) accumulated in soil OC in productive leucaena-grass pasture was estimated to be higher than the amount of CO2-e emitted in methane from beef production from these pastures, thus positively impacting on their greenhouse gas balance. Leucaena responses to P and/or S applications were evaluated in a 30 year-old leucaenagrass pasture. Leucaena RUE and symbiotic N2 fixation were restricted by S deficiency. Sulfur concentration in leaf tissue and high N:S ratio were useful indicators of S deficiency. Although leucaena growth and its nutritional status were little affected by P application, symbiotic N2 fixation did respond significantly to P application. Leucaena and grass responses to fertiliser applications were further evaluated at a variety of soil types and environments on 8 sites in Queensland. Increased leucaena RUE (from 3.1 to 4.6 kg total DM/ha/mm) and enhanced nutritional status at most sites showed that leucaena plants were restricted by P and/or S deficiency. The major factors contributing to the P and S deficiencies were: a) inherent low soil P and/or S fertility, b) nutrient removal by cropping and grazing, c) shallow soils, d) acid soils, and e) grass competition for available water and nutrients. Inter-row cultivation (with or without fertiliser) had little effect on leucaena growth but significantly increased grass RUE (from 4.7 to 7.0 kg total DM/ha/mm) at some sites probably due to enhanced mineralization of N. Leaf P and S concentrations were not reliable indicators of deficiencies of these nutrients, possibly due to inadequate leaf sampling conditions. The effects of ambient temperature, water stress and phenological development of plant on nutrient concentrations in leucaena leaf was investigated to determine whether leaf tissueanalysis can reliably predict nutrient deficiencies. The youngest fully expanded leaf (YFEL) was established as the most appropriate leaf tissue for predicting nutritional status of leucaena plants since the YFEL: (a) was an easily identifiable tissue in which nutrient shifts were at a minimum; (b) provided information for readily mobile (N, P and potassium) and variably mobile (S, copper and zinc) nutrients, thus simplifying leaf collection; and (c) facilitated comparison of data from leaves of similar physiological age in different growing conditions and sites. Nutrient concentrations in YFEL were significantly influenced by water stress and phenological stage of plant development (particularly flowering and pod filling) through the mechanism of rate of leaf appearance. Chronological age of the YFEL, an indicator of leaf appearance, varied from 12 to >70 days depending upon plant phenological stage, being >140 days under prolonged water stress. It was found that nutrient concentrations in leucaena YFEL can only be interpreted against critical concentrations if plants are actively growing (October-April) in a vegetative stage and YFEL are <20 days old. This will occur if there is no water stress for ≥28 days prior to sampling. A close correlation existed between chronological age of YFEL and leaf calcium (Ca) concentration. Calcium concentration could be used to assess the age of YFEL and thereby determine the suitability of tissue samples for nutrient analysis and interpretation. Leaves with Ca concentrations >0.7% DM should be discarded as they are likely to be too old (>20 days). The research program has identified that leucaena established on non-alluvial soils need to be provided with regular maintenance P and S fertiliser to promote symbiotic N2 fixation and to maintain high RUE. At present, many leucaena pastures are likely to be suffering undiagnosed nutrient deficiencies that will be limiting pasture and animal productivity and enterprise profitability. Youngest fully expanded leaf analysis can be used as a predictive tool to diagnose nutrient deficiencies provided the recommended protocol is followed. Further investigation is required to: a) assess the duration of responses to applied fertiliser to determine frequency of application; b) investigate the rate of maintenance fertiliser P and S that has to be applied to maintain leucaena symbiotic N2 fixation and RUE at a desired level to benefit both forage quality and quantity, and soil fertility; c) study methods of fertiliser placement for adequate and timely supply of nutrients, particularly P, to leucaena roots; and d) confirm the use of Ca concentration in YFEL as a predictor of optimum leaf age for the range of soils and areas where leucaena is grown.

A range of Proteaceous shrubs and other nursery plants were grown in containers with soilless media and various N levels. Plants demonstrated a range of responsiveness. Supplying soilless media with Osmocote (26% N) and other short term fertilisers proved to be a satisfactory method of studying the comparative nutrition of a wide range of container grown nursery plants using factorial experiments incorporating N, P, K and lime. Nutrient response surfaces were obtained using a central composite incomplete block design. Most Proteaceous shrubs were intolerant of high P levels due to excessive luxury consumption resulting in toxic foliar nutrient levels, especially in the presence of high N. Phosphorus sensitivity in plants appeared to correspond with the soil nutrient levels in their native habitat. This applied to species studied in the 2 main sub-families in the Proteaceae while similar findings were indicated for other Australian genera. A range of optimum N requirements in the Proteaceae was found – lowest needs for Protea which also had the greatest tolerance of very low fertiliser additions, compared to Grevillea robusta with much higher N requirements and strong foliage growth inhibition if nutrient levels are very low. Proteoid root growth on Grevillea rosmarinifolia only occurred at low nutrient levels and was not required for satisfactory foliage growth of container grown plants. Pot plants and seedlings, especially tomato, responded strongly to N and often there were positive NK interactions influencing foliage growth. Lime requirements were studied and in erica increasing lime rates depressed foliage growth. Comparative nutrition studies indicate that general or broad spectrum container media may be unsuitable for some groups of nursery plants and that they could be replaced by potting mixes designed to meet the widely differing needs of the species often grown. The number of specialist mixes would depend on the range of plants and be governed by management considerations.