Soil physico-chemical properties and water productivity of maize as affected by biochar application under different irrigation regimes in northwest India

Application of biochar as an amendment not only improves water retention in soil but also improves overall soil physical environment. To test this hypothesis, a field study was conducted for 2 years, i.e., 2019 and 2020, in an ongoing experiment on maize-based system at the Research Farm, Department of Soil Science, Punjab Agricultural University, Ludhiana, in a sandy loam soil. The parameters tested include soil water-holding capacity, moisture retention, water transmission characteristics, aggregate stability, bulk density, and penetration resistance of soil. Six biochar (B), farmyard manure (fym), and nitrogen (N) combinations were tested, which includes BN1 (biochar @ 7.5 t ha(-1) + N @ 75 kg ha(-1)), BN2 (biochar @ 7.5 t ha(-1) + N @ 150 kg ha(-1)), FN1 (fym @ 20 t ha(-1) + N @ 75 kg ha(-1)), FN2 (fym @ 20 t ha(-1) + N @ 150 kg ha(-1)), N1 (N @ 75 kg ha(-1)), and N2 (N @ 150 kg ha(-1)) in main plots and two irrigation regimes IW/CPE ratio 0.6 (I-0.6) and 0.9 (I-0.9) (irrigation water over cumulative open pan evaporation), i.e., deficit and full irrigation were in subplots. Moisture retention at 0.3 bar was significantly higher under biochar treatment BN1, i.e., 30.0%, while the lowest was recorded under N2, i.e., 25.5% at the end of spring 2020. Biochar and fym-amended soils decreased penetration resistance of soil by 22.57% and 20.85% at 10 cm soil depth as compared to unamended soil. BN1 showed increased mean weight diameter by 43.90% over N1 (control). Deficit irrigation, i.e., I-0.6, resulted in 6.11% and 18.78% higher water productivity of both kharif and spring maize, respectively, over I-0.9. It is also concluded that biochar as soil amendment may retain more water due to its porous nature and more surface area and also reduce the frequency of irrigation, hence sustaining and optimizing the limited water available for crop production in northwest India.