Combining organic and chemical fertilizer plus water-saving system reduces environmental impacts and improves apple yield in rainfed apple orchards

Combining organic and inorganic fertilizers is critical for increasing yield and improving soil fertility. However, the specific effects of this combination on greenhouse gas (GHG) emissions in hilly apple orchards remain unclear. Furthermore, studies on slope agriculture often overlook slope runoff, a significant factor to consider. Hence, we conducted a two-year field trial in a hilly apple orchard in north Shaanxi to investigate the impact of practical orchard measures on GHG emissions, runoff, apple yield, and fruit quality. Three management practices were implemented: (1) OCWS: combined organic and chemical fertilizers (substituting 60% chemical fertilizer with organic fertilizer) plus a water-saving system comprising a fish scale pit (FSP) and rainwater collection pit (RCP); (2) CWS: chemical fertilizer alone plus water-saving system; (3) CC: chemical fertilizer alone without water-saving system (the conventional practice based on local farmers' practices), serving as the control treatment. The results revealed that the OCWS treatment had the lowest average surface temperature (22.5 celcius), which was 5.5% and 4.5% lower than the CWS and CC treatments, and the highest surface soil volumetric water content (21.7%), which was 8.4% and 10.4% higher than the CWS and CC treatments during apple growing season. Seasonal variation in N2O, CO2, and CH4 emissions followed similar trends across treatments, although the magnitude of change varied. Cumulative N2O, CO2, and CH4 emissions did not differ significantly among treatments. Furthermore, the OCWS treatment had a similar global warming potential (GWP) to the CC treatment but a 62.6% lower greenhouse gas intensity (GHGI) than the CC treatment. Averaged across two years, the OCWS and CWS treatments significantly reduced runoff by 49.2% and 43.9% and sediment yield by 72.1% and 68.7%, respectively, compared to the CC treatment. Moreover, precipitation positively correlated 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 (69.4 kg hm-2 mm-1), transverse diameter (84.3 mm), single fruit weight (261.5 g), vitamin C (29.5 mg kg-1), soluble solids (14.3%), soluble sugars (10.7%), and sugar/acid ratio (55.0). Thus, the OCWS system is an effective management practice for improving apple yield and fruit quality and mitigating adverse environmental impacts on the Loess Plateau, with great potential in sustainable orchard management.

Automated summary

The combination of organic and inorganic fertilizers is crucial for increasing yield and improving soil fertility. This study conducted a field trial in hilly apple orchards and found that the use of organic fertilizers in a water-saving system can reduce greenhouse gas emissions, decrease runoff and sediment yield, and improve apple yield and fruit quality.