Organic and inorganic fertilizers combined with a water-saving technique increased soil fertilities and apple production in a rainfed hilly orchard

A high and stable apple yield is critical for rainfed hilly apple orchards; however, many factors threaten apple yield and sustainable apple production, including water shortage, soil erosion, and chemical fertilizer overuse. Therefore, we undertook a field trial with three treatments— (1) organic and inorganic fertilizer combining a water-saving technique (OIWS), (2) inorganic fertilizer combining a water-saving technique (IWS), and (3) inorganic fertilizer alone (CK)—to determine how to alleviate these yield-limiting factors and improve soil fertility. Averaged across five years (2016–2020), the OIWS treatment increased apple yield the most, by 24.87% and 67.34% relative to IWS and CK, respectively. The OIWS treatment also had the highest apple yield stability, despite no significant differences between treatments, indicating OIWS treatment could produce higher apple yield year by year relative to IWS and CK. In comparison to IWS and CK, OIWS treatment showed greater 0–1 m by 12.21% and 26.08% and 0–3 m soil water storage (SWS) by 14.81% and 19.12%, as well as the highest abundance of 0–1 m soil microaggregates (0.053–0.2 mm) and macroaggregates (0.2–2 mm). Moreover, relative to IWS and CK averaged across the five years and 0–2 m soil layers, OIWS treatment substantially enhanced soil organic carbon (SOC) by 4.23 and 3.93 g kg⁻¹ and total nitrogen (TN) by 0.09 and 0.11 g kg⁻¹, respectively. Furthermore, Changes in apple production were positively linked with variations in 0–1 m SWS, soil microaggregate and macroaggregate abundance, and SOC and TN. And the most relevant factor to apple yield is 0–1 m SWS. Overall, on the Loess Plateau, OIWS system is a sustainable approach for increasing apple productivity and soil fertilities in rainfed hilly orchards.