Effect of combining organic and chemical fertilizer plus water-saving system on greenhouse gas emissions, runoff, apple yield and quality in a hilly rainfed apple orchard

Combining organic and inorganic fertilizers is critical for increasing yield, reducing greenhouse gas (GHG) emissions, and improving soil fertility. However, the effect of combined organic and inorganic fertilizers on GHG emissions in hilly apple orchards is not clear. Furthermore, studies on slope agriculture mostly ignore slope runoff. Hence, a two-year field experiment was conducted in the hilly apple orchard in north Shaanxi to explore the effects of orchard management practices on surface soil water and temperature, GHG emissions, runoff, apple yield, and fruit quality. Three management practices were implemented: (1) combined organic and chemical fertilizer plus water-saving (OCWS) system; (2) chemical fertilizer plus water-saving (CWS) system; (3) conventional practice plus chemical fertilizer without water-saving system (CC). The results showed that, relative to CWS and CC treatments, the OCWS treatment decreased the average surface soil temperature during the apple growing period by 5.54% and 4.54% and increased surface soil water by 8.39% and 10.42%, respectively. Seasonal variation in N2O, CO2, and CH4 followed similar trends across treatments, but the amplitude of change varied. Soil water and temperature affected GHG emissions. Cumulative N2O, CO2, and CH4 emissions varied non-significantly among treatments. Furthermore, the OCWS treatment had a similar global warming potential (GWP) to the CC treatment. The OCWS treatment had a 39.33% lower greenhouse gas intensity (GHGI) than the CC treatment. Averaged across two years, the OCWS and CWS treatments significantly reduced runoff by 49.18% and 43.90% and sediment yield by 72.13% and 68.65% compared to the CC treatment. Furthermore, precipitation had a significant positive correlation with runoff and erosive sediment. Averaged across two years, the OCWS treatment had the highest apple yield (37,550 kg hm–2), crop water production (CWP) (69.40 kg hm–2 mm–1), transverse diameter (84.27 mm), single fruit weight (261.49 g), vitamin C (29.45 mg kg–1), soluble solids (14.28%), soluble sugars (10.74%), and sugar: acid ratio (54.95). The OCWS treatment is an effective management practice for increasing apple yield, improving fruit quality, and reducing adverse environmental impacts on the Loess Plateau in northwest China.