The degradation of soil quality due to undesirable farming practices has reached alarming scales in the Eastern Cape and this has had negative repercussions on soil productivity and the environment in general. There is growing evidence that conservation agriculture (CA) practices involving minimal mechanical disturbance, maintaining permanent surface cover and embracing diverse crop rotations increase soil organic carbon (SOC) and therefore has potential to mitigate soil quality deterioration. A study was carried out at two sites located in two ecotopes to investigate the effects of crop residue retention and crop rotations in a no till system on overall soil quality using the Soil Management Assessment Framework (SMAF) as the soil quality assessment tool. The CA study trials were laid out in 2012 at two different locations, one at the Phandulwazi Agricultural High school within the Phandulwazi Jozini ecotope and the other one at University of Fort Hare Research Farm within the Alice Jozini ecotope. The experiment was laid out as a split-split plot arrangement in a randomized complete block design with three replicates. Tillage treatments were applied on the main plots while crop rotation treatments were applied as subplots. Crop residue retention treatments were applied as sub-sub plots. The rotational treatments were maize-fallow-maize (MFM), maize-fallow-soybean (MFS), maize-wheat-maize (MWM) and maize-wheat-soybean (MWS). The initial assessment of the overall soil quality of the two ecotopes using the SMAF soil quality index (SQI) revealed that the soils at the Alice site were functioning at 80% while the soils at the Phandulwazi site were functioning at 79 percent of their optimum capacity. The slight difference in the soil quality of the two ecotopes could be attributed to their different soil organic C contents where the Alice Jozini ecotope had significantly higher soil organic C contents than the Phandulwazi Jozini ecotope. After 3 years of continuous treatment application, crop residue retention significantly improved most of the measured soil quality parameters. Generally across the sites, more soil organic C, microbial biomass C (MBC), ß-glucosidase (BG) activity, mineral N, extractable P and K, Cu, Zn, Mn, Fe, and macro-aggregates were recorded in treatments where crop residues were retained. Crop rotations alone did not have a significant impact on most of the measured soil quality indicators. The crop rotations influenced significantly the availability of mineral N across the two sites, highlighting the importance of using a legume in rotations on available N for the subsequent crops. Most of the measured soil attributes were not significantly influenced after 3 years of continuously applying combined treatment of CA components. Mineral N (NO3 + NH4), K, Zn and Fe were significantly impacted on by the interactions of CA components at the Phandulwazi site, while N, Cu, Zn and Mn were significantly increased at the Alice site. Low response of SOC to combined CA treatments in the short-term prompted the need to examine treatment effects on individual soil carbon fractions. The interaction of crop rotation and residue management techniques were significant on the fine particulate organic matter – C fractions and microbially respired C. These soil C fractions were more sensitive to short-term treatments of combined CA components than SOC and MBC, therefore they can be used as short-term indicators of CA effects on SOM. Soil organic carbon, MBC, extractable P and K, soil pH, EC, b, AGS (aggregate stability) and BG activity were measured and the Soil Management Assessment Framework (SMAF) used to calculate soil quality index (SQI) values for each treatment. The combination of the crop rotations with crop residue retention showed the potential to significantly improve SQI values in the long term. The highest soil quality improvement at both sites was achieved by the maize-wheat-soybean (MWS) rotation with crop residue retention.

Revegetation is a reclamation method used to stabilize land that has been disturbed (i.e. Uranium contamination) by mining in an effort to establish a sustainable plant community. During 1986-88, large amounts of topsoil were removed at the site adjacent to the Tuba City disposal cell to remove windblown contaminated soil and construct the Uranium disposal cell. Re-establishing a sustainable plant community is critical to minimizing dust emissions, controlling erosion, and improving rangeland condition, and enhancing evapotranspiration. The objective of this study was to evaluate the long-term effectiveness of revegetation efforts by 1) comparing plant species composition and abundance on the reclaimed area and native rangeland protected from grazing, 2) current rangeland condition by comparing plant communities on grazed and protected native rangeland 3) differences in soil fertility, particle size distribution, and morphology that could be influencing vegetation differences in the three areas, 4) landscape-scale evapotranspiration rates and effects on groundwater recharge in the three plant communities, and 5) the value of using relatively undisturbed Legacy Management parcels as reference areas. Plant cover in the revegetated area was greater in 2014 (24%) than in 1998 (15%); however, plant species composition and diversity in the revegetated area and in the reference area remained markedly different. The effectiveness of revegetation is improving, but given the extended amount of time the improvement is not matching the protected area’s percent cover. The reference area showed highest cover during the early cool-season. However, the grazed area possessed the highest plant species composition and highest foliar cover in the late warm-season. The vegetation relevé estimate and foliar cover statistics show the revegetated area (24%) was significantly less than the surrounding vegetation (35%), even after 26 years since original revegetation. These results are critical in assisting Legacy Management to identify environmentally sustainable methods for the continuous management of this site and others in the area.

Agriculture is facing increasing pressures to produce food that meets specific market and/or nutrition requirements, while using inputs in such a way that can ensure economic and environmental goals more efficiently. Two field experiments were conducted in 2013 and 2014 at the Royal Agricultural University’s Harnhill’ Manor Farm, Cirencester, UK to evaluate the influence of selected cultivation techniques, N fertilisation and undersowing legumes on spring wheat growth and development. To explore, in particular, the yield components contributing to grain yield and quality, as well as weed pressure influences together with changes in soil mineral N (SMN) content. Cultivation techniques included conventional tillage (CT), high intensity non-inversion tillage (HINiT) and low intensity non-inversion tillage (LINiT); mineral N fertilisation rates of 0, 70, 140 and 210 kg N ha-1 and two undersown legume species, black medic and white clover, plus no undersowing treatment. The performance of the management practices was strongly influenced by the weather. In 2013, under dry weather conditions, LINiT seems to be a suitable alternative to CT, while N fertilisation did not encourage greater grain yield. In 2014, CT appears to be a more reliable practice, while the application of up to 140 kg N ha-1 seemed to be enough to increase grain yield. Dry weather conditions at the time of broadcasting did not allow the undersowing species to be fully established, resulting in no effects on weed control and crop growth. In 2013, the initial poor plant establishment and slow crop growth under LINiT was compensated for by the soils ability to retain moisture, and thereby reducing crop water stress during the dry periods. This finally resulted in statistically similar grain yield to CT. In 2014 when water was not a limiting factor, poor plant establishment and crop growth, low SMN content and high weed pressure under LINiT resulted in lower grain yield than CT. In both years, HINiT resulted in low SMN content and high weed pressure resulting in poor grain yield. Across experiments, HINiT and LINiT saved energy-use and production costs, but CT could be more energy-use efficient and have high economic return if higher grain yield is assured. N fertilisation significantly promoted wheat growth, although under dry conditions with higher residual soil N, the N fertilisation did not increase yield. Under low SMN level applying up to 140 kg N ha-1 increased grain yield produced, but N fertilisation is energy consuming and its use does not always ensure a higher economic return.

No description available.

Biochar amendment to agricultural soils has been promoted for use in agricultural systems, both to mitigate global warming by increasing long-term soil carbon (C) sequestration and to enhance soil fertility and crop productivity. The objective of this study was to evaluate the effects of a single biochar application from peanut shell (Arachis hypogea L.) and mixed pine (Pinus spp.) wood to a Typic Hapludults in Blacksburg (VA, USA) and from peanut shell and eucalyptus (Eucalyptus camaldulensis) wood to a tropical, sandy, salt-affected soil in Ndoff (Fatick, Senegal) at 0, 10, and 20 Mg ha⁻¹ on soil chemical properties, inorganic nitrogen supply, and pearl millet production responses under field conditions for two growing seasons (2014 and 2015). Biochar application to temperate soils (Blacksburg) significantly increased total soil carbon, nitrogen, and plant available potassium in both years. In addition, pearl millet yields significant increased (53%) at the 20 Mg ha⁻¹ rate of peanut shell biochar in 2014 but did not persist in year 2. Beneficial effects largely appeared due to nutrient additions. Biochar treatment to tropical, sandy, salt-affected soils (Ndoff) had no effect on soil chemical properties. These results suggest that biochar application could improve soil fertility and crop productivity in temperate soils but had limited effects on tropical, sandy, salt-stressed soils in this study. The disparate results between these two field studies could be explained by differences in soil properties and climate, biomass feedstock, pyrolysis processes, and biochar handling, as well as experimental set-up. / Master of Science

Nitrification, the process whereby ammonical-nitrogen (NH i+4 - N) is changed into nitrate- nitrogen (NO3-N), is one of the more important biochemical processes associated with agriculture. Nitrate appears to be the form of N that most crops can most readily utilize.

No description available.

The purpose of this study was to analyze the different soils in Denton, Texas. For the purpose of this study, the soils of Denton County are divided into three general groups with respect to origin: 1)those formed in place by the weathering of consolidated rocks, 2) those formed from the weathering of unconsolidated rocks, and 3) alluvial soils. A chemical analysis of representative samples of Bell Clay, Kirvin fine sandy loam, and San Saba clay has been made, and shown to have a strict correlation with their respective geological origins.

A field experiment was conducted to evaluate the possibility of using shallow reservoirs containing aquatic plants to reduce excess nutrient levels of agricultural drainage effluent from organic soils. The reservoir systems consisted of three small reservoirs in series, containing separate stands of Eichhornia crassipes, Egeria densa and Typha sp., and a single large reservoir containing equal areas of all three aquatic plants. A control reservoir without plants was included. Drainage water from organic soils was pumped through each reservoir at 39.6 l/sec., 6 hours per day, 6 days per week. the major nutrients monitored in theses flow-through systems included nitrate-N, ammonium-N, total-N, ortho-P (soluble reactive phosphorus) and total-P. Temperature, pH, alkalinity, dissolved oxygen, carbon dioxide and turbidity were also monitored at the inflow and outflow of each reservoir system. Standing crop measurements and plant tissue analysis for nitrogen and phosphorus were conducted every 21 days. When a single large reservoir was used, effluent nitrate-N, ammonium-N, ortho-P and total-P concentrations decreased by 65%, 57.9%, 70.3% and 51% respectively, while organic-N concentrations increased by 7.2%. In the a series of small reservoirs the concentrations of nutrients decreased by 80%, 73%, 33%, 74%, and 70% for nitrate-N, ammonium-N organic-N, ortho-P and total-P respectively. The dissolved oxygen increased and turbidity was reduced in both reservoir systems. The bicarbonate and carbonate equilibrium in the series of reservoirs and control reservoir shifted to the carbonate sides as carbon dioxide was reduced. The carbon dioxide in the large reservoir remained at the same concentration throughout the study. The standing crop in both reservoir systems was similar with an average of 11.6 mt/ha grown in R-1 and 11.2 mt/ha grown in the series of reservoirs. The nitrogen retained during the study was 1017 kg/ha and 750 kg/ha in the series and the large reservoir respectively. Phosphorus retained in the series was 249 kg/ha while the large reservoir retained 211 kg/ha of phosphorus. The series of reservoirs was more effective in reducing the nutrient levels of the drainage effluent than the large single reservoir. The results obtained from this study indicated that reservoirs in series can be used to reduce excess nutrient levels of agricultural drainage waters. However, further studies are necessary to increase the efficiency of the system and to accelerate plant removal. The physical, chemical, and biological processes involved in removal of the nitrogen and phosphate should be optimized in future applications.

M.S.