Different carbon sources enhance system productivity and reduce greenhouse gas intensity

The aim of this study was to investigate the effect of biochar, straw and nitrogen (N) fertilizer on soil properties, crop yield and greenhouse gas intensity in rainfed spring wheat (Triticum aestivum L.), and to produce background dataset to improve nutrient management guidelines for semiarid environments. The two carbon sources (straw and biochar) were applied alone or combined with nitrogen fertilizer (urea, 46% N), whilst the soil without carbon amendment was fertilized by urea in the rates 0, 50 and 100 kg N/ha. The experiments were arranged in a randomized complete block design with three replicates. The greatest yields were found with 100 kg N/ha under biochar, straw and soils without carbon. Biochar treated soils produced the greatest grain yield at 1906 kg/ha, followed by straw at 1643 kg/ha, and soils without carbon at 1553 kg/ha. This was explained by increased easily oxidizable carbon and total soil nitrogen in the biochar treated soil (P < 0.05). Straw treated soils and soils without carbon increased global warming potential by 13% and 14% compared to biochar amended soils. The biochar amended treatment also improved easily oxidizable carbon and total nitrogen (P < 0.05), which supported the above results. BN100 (15 t/ha biochar + 100 kg N/ha) reduced greenhouse gas intensity by approximately 30% compared to CN100 (100 kg N/ha applied each year) and SN50 (4.5 t/ha straw applied each year + 50 kg N/ha). Based on these results, biochar could be used with N-fertilizer as a soil conditioner to improve yield and reduced greenhouse gas intensity.