Effects of different ratios of organic and inorganic fertilizer on rice yield and soil physicochemical properties under conventional and controlled irrigation conditions

Water and fertilizer management practices are critical in rice fields. Excessive application of fertilizer adversely affects soil physicochemical properties, consequently decreasing yield. A greenhouse experiment was conducted to determine the effect of high (L1), medium (L2) and low organic fertilizer ratios (L3) as well as chemical fertilizer alone (L4) and no fertilization (L5) under conventional (C) and controlled irrigation (M) on rice yield and soil characteristics. Statistically, the regression equation was developed by using principal component analysis to clarify the influence of different soil quality factors on rice yield. The results showed that controlled irrigation could increase soil temperature (ST), electrical conductivity (EC) and nitrogen content while decreasing soil pH. The application of organic fertilizer enhanced ST and decreased EC. Under equal nitrogen application conditions, rice yield increased with organic fertilizer application, and it was highest under L1, which was 2.7% higher than L4 and 22% higher than L5. In the case of irrigation methods, controlled irrigation application increased yield by 6% compared to conventional irrigation. The multiple linear regression equation showed that the cumulative contribution of variance of the two principal component eigenvalues reached 75%, among which soil pH, total nitrogen (TN) content and nitrate nitrogen (NO3--N) contributed positively to yield, while ammonium nitrogen (NH4+-N), soil organic carbon (SOC), EC and ST showed negative effects on rice yield. Thus, our study findings can provide a scientific basis for improving management practices.