Interactive Effects of Maize Straw-Derived Biochar and N Fertilization on Soil Bulk Density and Porosity, Maize Productivity and Nitrogen Use Efficiency in Arid Areas

Many of published studies have focused on the application of organic amendments such as straw and biochar to dryland agricultural soils with respect to soil properties, crop production, and soil carbon sequestration. Nevertheless, the relative effects of straw and straw-derived biochar application on soil structure, water and fertilizer use efficiency, and yield of maize under drip irrigation are yet to be explored. A 2-year field experiment was conducted to evaluate the influence of straw and biochar application on soil bulk density, soil porosity, and hydro-physical properties and to optimize an agronomic strategy for enhancing maize productivity and water and nitrogen utilization efficiency in arid areas. Three straw incorporation methods, (i) no straw incorporation (T), (ii) straw incorporation (S), and (iii) straw-derived biochar application (B), and four nitrogen fertilizer rates, (i) no nitrogen application (N-0), (ii) medium nitrogen (N-225, 225 kg ha(-1)), (iii) traditional nitrogen (N-300, 300 kg ha(-1)), and (iv) high nitrogen (N-375, 375 kg ha(-1)), were used as treatments. Our results indicated that both S and B improved soil structure (soil porosity) and water storage in 0-60 cm soil profile. Compared with T, the average grain yield increased by 3.7-7.1% and 5.8-15.6% under S and B treatments, respectively, while water use efficiency (WUE) was improved by 2.0-13.0% and 6.2-17.5%. Compared to S, B effectively improved the soil structure, soil water consumption from deep layers (80-200 cm), and dry matter accumulation at later growth stage (V12-R6). Nitrogen application significantly enhanced the water consumption in 0-200 cm soil layer and increased straw and grain yield, which increased with increasing the N rates. A positive interactive effect between straw incorporation methods and nitrogen application rates was observed. Under straw-derived biochar application, medium dose of N recorded significantly the highest grain yield (average 13.78 t ha(-1)), WUE (average 21.2 kg ha(-1) mm(-1)), and nitrogen agronomic efficiency (NAE) in comparison with T with traditional N application rate. Straw-derived biochar application with 225 kg ha(-1) N could be an efficient strategy leading to improved water and N use efficiency and productivity of spring maize under drip irrigation. However, due to the high economic input of biochar compared with straw, widespread use of biochar in agriculture still needs more institutional and technical support.