Development of DNDC-BC model to estimate greenhouse gas emissions from rice paddy fields under combination of biochar and controlled irrigation management.

Acknowledgments This work was supported by the National Natural Science Foundation of China 608 (51879076), SuperG (Nr: 774124; funded under EU Horizon 2020 programme), the Fundamental Research Funds for the Central Universities (B220203009), the Postgraduate Research & Practice Program of Jiangsu Province (KYCX22_0669), the Water Conservancy Science and Technology Project of Jiangxi Province 12 (202124ZDKT09). Thanks to the late Professor Changsheng Li who provided the source code of DNDC and corresponding support. We thank the China Scholarship Council (CSC) for providing a scholarship to Zewei Jiang.Peer reviewedPublisher PD

Are there environmental or agricultural benefits in using forest residue biochar in boreal agricultural clay soil?

Short-term agronomic and environmental benefits are fundamental factors in encouraging farmers to use biochar on a broad scale. The short-term impacts of forest residue biochar (BC) on the productivity and carbon (C) storage of arable boreal clay soil were studied in a field experiment. In addition, rain simulations and aggregate stability tests were carried out to investigate the potential of BC to reduce nutrient export to surface waters. A BC addition of 30 t ha−1 increased soil test phosphorus and decreased bulk density in the surface soil but did not significantly change pH or water retention properties, and most importantly, did not increase the yield. There were no changes in the bacterial or fungal communities, or biomasses. Soil basal respiration was higher in BC-amended plots in the spring, but no differences in respiration rates were detected in the fall two years after the application. Rain simulation experiments did not support the use of BC in reducing erosion or the export of nutrients from the field. Of the C added, on average 80% was discovered in the 0–45 cm soil layer one year after the application. Amendment of boreal clay soil with a high rate of BC characterized by a moderately alkaline pH, low surface functionalities, and a recalcitrant nature, did not induce such positive impacts that would unambiguously motivate farmers to invest in BC. BC use seems unviable from the farmer's perspective but could play a role in climate change mitigation, as it will likely serve as long-term C storage.202

Innovative Water Management Using Advanced Irrigation Systems and Biochar

Two approaches to water optimization in agriculture are to increase soil water retention and improve the efficiency of irrigation. A soil amendment that has received attention for its ability to increase soil water retention is biochar, the remaining biomass after high C materials have been pyrolyzed (burned with limited oxygen and heat). Two studies were conducted at a total of 10 site-years in Utah from 2018 to 2020 to evaluate how wood biochar influences the productivity and crop quality of irrigated alfalfa (Medicago Sativa L.), corn (Zea mays L.), and wheat (Triticum L.), along with soil water tension. One study included a single biochar rate of 22 Mg ha-1 at two irrigation levels (full vs. partial), where soil-incorporated biochar increased silage corn yield by 12% in 2018 and reduced yield by 10% in 2019. Top-dressed biochar had no impact on alfalfa yield from 2018-2020, in either irrigation rate. The other trial had six to seven biochar rates (0 – 67 Mg ha-1), plus the addition of wood chips at a single rate (22 Mg ha-1) at one site. This trial displayed a yield decrease of 0.01 Mg ha-1 of wheat grain for each additional Mg ha-1 of biochar applied, however there were no impacts on silage corn production. Data obtained over ten site years showed minimal impacts from biochar on crop yield, quality, or soil water tension, leading us to conclude that wood biochar was not an effective tool for enhancing crop production or conserving irrigation water in arid agriculture. Most pivot sprinkler package in the Intermountain West are classified as mid-elevation sprinkler application (MESA). Several studies of low elevation spray application (LESA), low energy precision application (LEPA), and mobile drip irrigation (MDI) have demonstrated greater efficiency than MESA, due to less loss between the time that the irrigation water leaves the nozzle and enters the rootzone. However, these advanced sprinkler packages have rarely been tested at a reduced application rate. Eight site-years of data were collected at four Utah farms from 2018 to 2020, to evaluate crop yield and quality responses to full and reduced rates of each system in alfalfa, corn, and small grains. Soil water tension was also measured. Data showed that the advanced systems were sometimes able to maintain yield and quality while applying 15 to 25% less water, yet there were situations where MESA outperformed the advanced systems. This led us to conclude that there is not one style that will have the best results all the time, but that tailoring the package to the field characteristics is where the optimization with these packages can occur. Therefore, this chapter is being published as an Extension Guidebook for farmers

Innovative use of Rice Husk Biochar for Rice Cultivation in Salt-affected Soils with Alternated Wetting and Drying Irrigation

Nakhon Ratchasima, Thailand, is the most severely salt-affected area in the country’s Northeast region caused by the underlying geology and human activities. In this condition, evaporation of groundwater with salt to the soil surface is an important issue that affects the use of the area primarily for agricultural purposes. This research aimed to improve saline soil quality using rice husk biochar (RHB) to enable rice cultivation. The experiment was designed to limit the evaporation of salty groundwater by cultivating rice in the cement pond. A mixture of different amounts of RHB with four replicates at 0%, 1%, 1.5%, and 2.0% by weight (wt.%) and 500 g dried cow manure were used for rice cultivation. Jasmine rice variety KDML 105 was planted in cement ponds filled with saline sodic soil at pH 10.6, with a total sodium content of 0.83%, electrical conductivity of 68.6 dS/m, and SAR of 11,707. The results indicated that RHB could significantly reduce the soil salinity, EC, Na+ content, and SAR value while elevating the levels of available macronutrients within just one crop of rice cultivation (120 days). In addition, salt evaporation from groundwater to the soil surface can be limited. The study demonstrated that mixing RHB at 1.5% wt into the saline soil can improve the salted soil and yield the highest rice production. Applying RHB in saline sodic soil for rice cultivated in cement pond is an alternative way for salt-affected areas to reach food security and long-term salted soil revitalization