Soil water, nutrient distribution and use efficiencies under different water and fertilizer coupling in an apple–maize alley cropping system in the Loess Plateau, China

Soil Moisture, Nutrients, and Plant Growths under Various Irrigation and Fertilization Regimes during the Crop Replacement Period in an Alley Intercropping System on the Loess Plateau of China

“…This result was consistent with a previous study, which also revealed that the yield of intercropped soybean decreases instead of increasing when the irrigation amount exceeds 80% of the field capacity. The study provided possible explanations for this phenomenon, including a decrease in soil porosity, leaching of nutrients, and increased ecological niche overlap between the surface crop roots and deep tree roots due to excessive irrigation [20]. We also found that the maximum values of soybean plant height were observed in treatments DI 1 F 0 , FI 2 F 0 , and DI 2 F 2 during the three growth stages of branching, podding, and filling, respectively.…”

“…Based on the soil moisture range suitable for growing apples and crops [23,24], three irrigation levels were set: rain-fed (I 0 ), 50% of the average field capacity (after irrigation) (I 1 ), and 80% of the average field capacity (upper limit of irrigation) (I 2 ), respectively. There were not many days during the crop growing season when the average soil moisture content at 0-60 cm depth in the area was below 50% of the field capacity [20,23]. We used two irrigation methods, drip irrigation (DI) and flood irrigation (FI), and tested three fertilizer application rates: no fertilizer (F 0 ), 50% of the locally applied fertilizer rate (375 kg/hm 2 (F 1 )), and 100% of the locally applied fertilizer rate (750 kg/hm 2 (F 2 )).…”

“…After washing away the soil, apple tree and crop roots were separated using a 2 mm sieve and scanned using the WinRHIZO software (v. 2007, Reagent Instruments Inc., Quebec, QC, Canada) to measure total root length (mm), total root surface area (cm 2 ), average root diameter (cm), and total root volume (cm 3 ) (Figure 8). We used linear regression analyses and quadratic function fitting (Q) between crop photosynthetic parameters and soil nutrient values at four distances from the trees to investigate the interactions between apple trees and crops, and crop distances from the trees [20]. The linear regression coefficients of each treatment were calculated to characterize the effects of each treatment on interspecific competition.…”

“…We used linear regression analyses and quadratic function fitting (Q) between crop photosynthetic parameters and soil nutrient values at four distances from the trees to investigate the interactions between apple trees and crops, and crop distances from the trees [20]. The linear regression coefficients of each treatment were calculated to characterize the effects of each treatment on interspecific competition.…”

“…Our team has previously conducted research on water and nutrient regulation in flood and drip irrigation systems in the Loess Plateau region, and the results showed that both irrigation methods can improve productivity under suitable water and nutrient input levels [20,21]. However, our previous studies were carried out on continuous cropping systems, and it remains unclear how best to regulate water and fertilizer inputs during the crop replacement period because crop replacement may create more uncertainty in soil water and nutrient changes [22].…”