Productivity gains in vegetables from rice husk biochar application in nutrient-poor soils in Timor-Leste.

Response to fertilisation with biochar is greatest in field crops on acidic tropical soils, but limited information is available for vegetable crops. As a case-study using vegetable production in Timor-Leste, we assessed if biochar alleviates nutritional constraints to vegetables in low-nutrient soils. Field trials on vegetable crops were conducted with fertiliser combinations of rice husk biochar, phosphate and local fertiliser at three sites. A pot soil incubation trial of biochar was undertaken with soil from the acid site, where rice husk biochar had a larger effect on productivity than the other fertilisers in chili pepper, tomato and soybean with an average yield increase with biochar of 230% over control. Combining phosphate with biochar augmented the yield over biochar alone in chili pepper, tomato and soybean. At neutral and alkaline sites, fertilisation with biochar lifted mean yield over the control. Soil constraints alleviated by fertiliser were primarily from P and Zn deficiencies. Marked increases in vegetable yields, among the highest globally, were achieved with fertilisation with biochar individually and in combination with phosphate in low nutrient soil in Timor-Leste. Clearly, rice husk biochar is a promising avenue to fertilise the soil with P and Zn and increase crop productivity in Timor-Leste.

Genetic aluminium resistance coupled with foliar magnesium application enhances wheat growth in acidic soil.

BACKGROUND: Soil acidity causes an increase in the solubility of toxic aluminium (Al), inhibiting root growth and limiting plant access to soil water and nutrients. Toxicity of Al decreases growth and development more in Al-sensitive than Al-resistant wheat (Triticum aestivum L.) genotypes. Applying magnesium (Mg) may alleviate Al toxicity in acidic soil. It is unclear if growing Al-resistant wheat, coupled with Mg application, will enhance wheat growth and physiological responses in acidic soil. Wheat was grown in the reconstituted acidic soil profile in a three-factor glasshouse experiment comprising foliar Mg at [Mg] = 0 and 200 mg L-1 (using magnesium sulfate), wheat genotypes ES8 (Al sensitive) and ET8 (Al resistant), and four soil treatments [non-amended soil (pH0.1 M CaCl2 4.0); 100% of the recommended lime dose in subsoil to raise pH to 6.0; or 20 mg Mg kg-1 soil to the whole soil profile (as magnesium sulfate or magnesium chloride)]. RESULTS: Applying foliar Mg to Al-resistant wheat significantly increased shoot dry weight (24%), subsoil root dry weight (12%), subsoil coarse (>0.2 mm in diameter) root length (12%), net photosynthetic rate (28%), and total leaf area (10%) compared with plants not treated with foliar Mg. Combining foliar Mg application with subsoil liming increased the subsoil total root length by 1.3-fold compared with zero foliar Mg. Without foliar Mg, subsoil liming and soil Mg amendment significantly (by 10%) enhanced shoot growth and total leaf area compared with non-amended soil. CONCLUSION: Growing an Al-resistant genotype coupled with applying Mg foliarly and to soil improved wheat growth in an acidic soil. © 2021 Society of Chemical Industry.

Global Research Alliance N2 O chamber methodology guidelines: Guidelines for gap-filling missing measurements.

Nitrous oxide (N2 O) is a potent greenhouse gas that is primarily emitted from agriculture. Sampling limitations have generally resulted in discontinuous N2 O observations over the course of any given year. The status quo for interpolating between sampling points has been to use a simple linear interpolation. This can be problematic with N2 O emissions, since they are highly variable and sampling bias around these peak emission periods can have dramatic impacts on cumulative emissions. Here, we outline five gap-filling practices: linear interpolation, generalized additive models (GAMs), autoregressive integrated moving average (ARIMA), random forest (RF), and neural networks (NNs) that have been used for gap-filling soil N2 O emissions. To facilitate the use of improved gap-filling methods, we describe the five methods and then provide strengths and challenges or weaknesses of each method so that model selection can be improved. We then outline a protocol that details data organization and selection, splitting of data into training and testing datasets, building and testing models, and reporting results. Use of advanced gap-filling methods within a standardized protocol is likely to increase transparency, improve emission estimates, reduce uncertainty, and increase capacity to quantify the impact of mitigation practices.

Simulating response of N2O emissions to fertiliser N application and climatic variability from a rain-fed and wheat-cropped soil in Western Australia.

BACKGROUND: Besides land management and soil properties, nitrous oxide (N(2)O) emissions from the soil may be responsive to climatic variation. In this study the Water and Nitrogen Management Model (WNMM) was calibrated and validated to simulate N(2)O emissions from a rain-fed and wheat-cropped system on a sandy duplex soil at Cunderdin, Western Australia, from May 2005 to May 2007, then it was deployed to simulate N(2)O emissions for seven scenarios of fertiliser N application under various climatic conditions (1970-2006). RESULTS: The WNMM satisfactorily simulated crop growth, soil water content and mineral N contents of the surface soil (0-10 cm), soil temperatures at depths and N(2)O emissions from the soil compared with field observations in two fertiliser treatments during calibration and validation. About 70% of total N(2)O emissions were estimated as nitrification-induced. The scenario analysis indicated that the WNMM-simulated annual N(2)O emissions for this rain-fed and wheat-cropped system were significantly correlated with annual average minimum air temperature (r = 0.21), annual pan evaporation (r = 0.20) and fertiliser N application rate (r = 0.80). Both annual rainfall and wheat yield had weak and negative correlations with annual N(2)O emissions. Multiple linear regression models for estimating annual N(2)O emissions were developed to account for the impacts of climatic variation (including temperature and rainfall), fertiliser N application and crop yield for this rain-fed and wheat-cropped system in Western Australia, which explained 64-74% of yearly variations of the WNMM-estimated annual N(2) O emissions. CONCLUSION: The WNMM was tested and capable of simulating N(2) O emissions from the rain-fed and wheat-cropped system. The inclusion of climatic variables as predictors in multiple linear regression models improved their accuracy in predicting inter-annual N(2)O emissions.

Biodiesel production in a semiarid environment: a life cycle assessment approach.

While the use of biodiesel appears to be a promising alternative to petroleum fuel, the replacement of fossil fuel by biofuel may not bring about the intended climate cooling because of the increased soil N2O emissions due to N-fertilizer applications. Using a life cycle assessment approach, we assessed the influence of soil nitrous oxide (N2O) emissions on the life cycle global warming potential of the production and combustion of biodiesel from canola oil produced in a semiarid climate. Utilizing locally measured soil N2O emissions, rather than the Intergovernmental Panel on Climate Change (IPCC) default values, decreased greenhouse gas (GHG) emissions from the production and combustion of 1 GJ biodiesel from 63 to 37 carbon dioxide equivalents (CO2-e)/GJ. GHG were 1.1 to 2.1 times lower than those from petroleum or petroleum-based diesel depending on which soil N2O emission factors were included in the analysis. The advantages of utilizing biodiesel rapidly declined when blended with petroleum diesel. Mitigation strategies that decrease emissions from the production and application of N fertilizers may further decrease the life cycle GHG emissions in the production and combustion of biodiesel.