Fungal contributions to soil aggregation and soil quality

Conceptual models implicate the fungi as important mechanisms in soil aggregate formation but the lack of suitable assays for routine quantification of fungal biomass make validation of these models evasive. The objectives of these studies were threefold: (1) to evaluate the effectiveness of ergosterol as an indicator of fungal biomass; (2) to evaluate interrelationships between aggregate-forming processes induced by fungi and those caused by physical and chemical factors; (3) to evaluate potential soil quality indicators under different tillage and residue management systems. Objective 1 focused on determining the efficiency of recovering ergosterol from spiked soil samples and measuring ergosterol of nine fungal species. Objective 2 involved a series of laboratory experiments using two autoclaved soils, residue additions (ground alfalfa (Medicago sativa) and reed canarygrass (Phalaris arundinacea)), and freeze/thaw and wet/dry cycles in a factorial design with three replicates for each factor (i.e., a total of 108 experimental units). Objective 3 evaluated wet aggregate stability, microbial biomass, respiration, total C and N, and soil ergosterol content as a function of tillage or residue management in field studies at three research farms. Results indicate the ergosterol assay (Objective 1) has low variability and high extraction efficiency. Fungal ergosterol content ranged from 0.38 to 10.40 mg kg[superscript]-1. Addition of Chaetomium sp. to autoclaved soil resulted in increased aggregation (Objective 2). Subjecting autoclaved soil samples to either freeze/thaw cycles, wet/dry cycles, or crop residue additions decreased aggregation, suggesting that the mechanism by which crop residues increase aggregation is through stimulation of the fungal biomass. Residue, in the absence of Chaetomium sp., actually decreased aggregation. Field study results (Objective 3) indicate that crop residue management impacts fungal populations with corresponding changes in aggregate stability. This research suggests that ergosterol is an effective indicator of living fungal biomass and that fungi are important mediators of aggregate formation and stabilization. These studies suggest that aggregate stability and ergosterol content can be used as indicators for assessing soil quality. As we strive for sustainability in our agricultural systems, an improved understanding of interactions between soil management practices and fungal populations is an important consideration

Conservation Agriculture and Household Wellbeing: A Non-Causal Comparison among Smallholder Farmers in Mozambique

This research examines the relationship between household wellbeing and the use of conservation agriculture (CA) by smallholder farmers in Mozambique. Wellbeing indicators are regressed on household demographic attributes, farm management practices, and a variable indicating farmer adoption of CA. Findings suggest that households using CA have higher wellbeing index scores related to farm tool and implement ownership and housing material quality, but lower index scores related to livestock ownership. The findings present an encouraging, baseline picture of the association between the use of CA technologies by farmers in Mozambique and household wellbeing

Cassava (Manihot esculenta Crantz) Tuber Quality as Measured by Starch and Cyanide (HCN) Affected by Nitrogen, Phosphorus, and Potassium Fertilizer Rates

Cassava (Manihot esculenta Crantz) is an important subsistence crop for many poor rural families in Africa. Cassava contains cyanogenic glucosides (linamarin and lotaustralin) which liberate hydrogen cyanide (HCN) during tuber processing. Once liberated, HCN attaches to the processed tuber. Continuous consumption of processed tuber containing high HCN concentration coupled with low protein intake causes Konzo – a paralyzing disorder that impacts children and women of childbearing age. There are ways to reduce HCN concentration during tuber processing; however, this can also reduce the overall starch content in the cassava tuber. A study comprising twenty treatments consisting of different combinations of nitrogen (N), phosphorus (P), and potassium (K) fertilizer rates was initiated in 2013 in the coastal Dondo District of Mozambique to assess cassava tuber quality as measured by starch and HCN. Significant differences were observed in starch content (CSC) of unprocessed tubers due to combined addition of N, P and K fertilizer rates, sample size, and estimation procedure. However, no significant differences were observed in HCN concentration in tubers due to the addition of N, P and K fertilizer. The HCN concentration in cassava tuber appears to be a function of the physiology of the crop or possibly cassava variety rather than the environment or conditions under which the crop is grown

A Short-Term Assessment of Carbon Dioxide Fluxes under Contrasting Agricultural and Soil Management Practices in Zimbabwe

Two of the biggest problems facing humankind are feeding an exponentially growing human population and preventing the accumulation of atmospheric greenhouse gases and its climate change consequences. Refined agricultural practices could address both of these problems. The research addressed here is an exploration of the efficacy of alternative agricultural practices in sequestering carbon (C). The study was conducted in Zimbabwe with the intent to (a) demonstrate the utility of micrometeorological methods for measuring carbon dioxide (CO2) exchange between the surface and the atmosphere in the short-term, and (b) to quantify differences in such exchange rates for a variety of agricultural practices. Four Bowen ratio energy balance (BREB) systems were established on the following agricultural management practices: (1) no-till (NT) followed by planting of winter wheat (Triticum aestivum), (2) NT followed by planting of blue lupin (Lupinus angustifolios L.), (3) maize crop residue (Zea mays L.) left on the surface, and (4) maize crop residue incorporated with tillage. Over a period of 139 days (from 15 June to 31 October 2013) the winter wheat cover crop produced a net accumulation of 257 g CO2-C m-2, while the tilled plot with no cover crop produced a net emission of 197 g CO2-C m-2 and the untilled plot with no cover emitted 235 g CO2-C m-2. The blue lupin cover crop emitted 58 g CO2-C m-2, indicating that winter cover crops can sequester carbon and reduce emissions over land left fallow through the non-growing season. The micrometeorological methods described in this work can detect significant differences between treatments over a period of a few months, an outcome important to determine which smallholder soil management practices can contribute towards mitigating climate change

Abiotic Stresses Management in Citrus

Citrus production is affected globally by several environmental stresses. Some citrus-producing regions suffer from severe ecological abiotic stresses, including cold, soil salinity and sodicity, extreme temperature, and drought. These abiotic stresses can alleviate the growth, fruit yield, and quality of citrus. Strategies that attempt to sustain and increase tolerance of citrus against the negative effect of abiotic stresses are the use of antiperspirant compounds, phytohormones, synthetic and natural growth regulators, soil and plant moisture retaining tools and structures, nutrition management, application of organic fertilizers, rootstocks breeding in citriculture, and others. These strategies increase the yield and growth of the plant along with the relative improvement of the fruit quality during the growth and fruiting period, increasing the absorption of water and nutrients, the extensive accumulation of osmolytes and the increase of antioxidant enzymes, changes in the amount of signaling substances, and the expression of genes under stress, increase tolerance to abiotic stresses in citrus fruits. In this review, we tried to provide a summary of the abiotic stress management in citrus by literature

Associated health risks from heavy metal-laden effluent into point drainage channels in Faisalabad, Pakistan

Industrial effluent discharge has increased due to rapid urbanization and industrialization. Irrational use of this water for irrigation has caused environmental and health issues. The objective of the current study is to evaluate the treated effluents of textile, ghee and chemical industries for major heavy metals (Cd, Cr, Ni, Pb and Fe) and other basic analysis (pH, EC, TSS and TDS). Effluent samples were collected from the discharge of industries entering into main wastewater collecting channel located in Faisalabad city. Heavy metals contents were determined via atomic absorption spectrophotometry. Results showed that the highest pH (11.06) was recorded in textile effluent while EC (7.89mS/cm), TSS (1185.55mg/L) and TDS (6317.33mg/L) were found highest in chemical industrial effluents. Heavy metals contents were determined through atomic absorption spectrophotometer. The mean comparison of heavy metal concentration (mg/L) showed the concentration of Cd, Cr and Ni were within the safe limits; however, Fe and Pb were higher than the safe limits in all industrial effluents. The highest/unsafe concentration of metal Fe was recorded 4.093, 2.979 and 2.959 mg/L in the effluents of chemical, textile and ghee mill respectively. While the highest/unsafe concentration of metal Pb was recorded 0.643, 0.578 and 0.286 mg/L in the effluents of textile, chemical and ghee mill respectively. The permissible limits of heavy metals Fe and Pb is 0.5 and 2 mg/L respectively. We conclude that before discharge into a receiving stream, the effluents must be treated more time with a treatment method that removes Pb and Fe within standard limits else the discharge will pose pollution and health risks to human beings

Nutrient Source and Tillage Effects on Maize: II. Yield, Soil Carbon, and Carbon Dioxide Emissions

There is a need to understand the potential benefits of using the biotechnology waste by‐product from manufacturing as a fertilizer replacement in agriculture, by quantifying the economic value for the farmer and measuring the environmental impact. Measuring CO2 emissions can be used to assess environmental impact, including three widely used micrometeorological methodologies: (i) the Bowen Ratio Energy Balance (BREB), (ii) aerodynamic flux‐gradient theory, and (iii) eddy covariance (EC). As a first step in quantifying benefits of applying biotechnology waste in agriculture, a detailed examination of these three methods was conducted to understand their effectiveness in quantifying CO2 emissions for this specific circumstance. The study measured micrometeorological properties over a field planted to maize (Zea mays L. var. indentata ), one plot treated with biotechnology waste applied as a nutrient amendment, and one plot treated with a typical farmer fertilizer practice. Carbon dioxide flux measurements took place over 1 yr, using both BREB and EC systems. The aerodynamic method was used to gap‐fill BREB system measurements, and those flux estimates were compared with estimates produced separately by the aerodynamic and EC methods. All methods found greater emissions over the biotechnology waste application. The aerodynamic method CO2 flux estimates were considerably greater than both the EC and a combined BREB‐aerodynamic approach. During the day, the EC and BREB methods agree. At night, the aerodynamic approach detects and accounts for buildup of CO2 at the surface during stable periods. The BREB systems combined with aerodynamic approaches provide alternate methods to EC in examining micrometeorological properties near the surface

Nutrient Source and Tillage Effects on Maize: I. Micrometeorological Methods for Measuring Carbon Dioxide Emissions

There is a need to understand the potential benefits of using the biotechnology waste by‐product from manufacturing as a fertilizer replacement in agriculture, by quantifying the economic value for the farmer and measuring the environmental impact. Measuring CO2 emissions can be used to assess environmental impact, including three widely used micrometeorological methodologies: (i) the Bowen Ratio Energy Balance (BREB), (ii) aerodynamic flux‐gradient theory, and (iii) eddy covariance (EC). As a first step in quantifying benefits of applying biotechnology waste in agriculture, a detailed examination of these three methods was conducted to understand their effectiveness in quantifying CO2 emissions for this specific circumstance. The study measured micrometeorological properties over a field planted to maize (Zea mays L. var. indentata ), one plot treated with biotechnology waste applied as a nutrient amendment, and one plot treated with a typical farmer fertilizer practice. Carbon dioxide flux measurements took place over 1 yr, using both BREB and EC systems. The aerodynamic method was used to gap‐fill BREB system measurements, and those flux estimates were compared with estimates produced separately by the aerodynamic and EC methods. All methods found greater emissions over the biotechnology waste application. The aerodynamic method CO2 flux estimates were considerably greater than both the EC and a combined BREB‐aerodynamic approach. During the day, the EC and BREB methods agree. At night, the aerodynamic approach detects and accounts for buildup of CO2 at the surface during stable periods. The BREB systems combined with aerodynamic approaches provide alternate methods to EC in examining micrometeorological properties near the surface

Conservation agriculture as a climate change mitigation strategy in Zimbabwe

There is a need to quantify agriculture’s potential to sequester carbon (C) to inform global approaches aimed at mitigating climate change effects. Many factors including climate, crop, soil management practices, and soil type can influence the contribution of agriculture to the global carbon cycle. The objective of this study was to investigate the C sequestration potential of conservation agriculture (CA) (defined by minimal soil disturbance, maintaining permanent soil cover, and crop rotations). This study used micrometeorological methods to measure carbon dioxide (CO2) flux from several alternative CA practices in Harare, central Zimbabwe. Micrometeorological methods can detect differences in total CO2 emissions of agricultural management practices; our results show that CA practices produce less CO2 emissions. Over three years of measurement, the mean and standard error (SE) of CO2 emissions for the plot with the most consistent CA practices was 0.564 ± 0.0122 g CO2 m-2 h-1, significantly less than 0.928 ± 0.00859 g CO2 m-2 h-1 for the conventional tillage practice. Overall CA practices of no-till with the use of cover crops produced fewer CO2 emissions than conventional tillage or fallow