Soil amendments improved physiological characteristics, grain yield, and water use efficiency of common buckwheat under multi-year continuous cropping
Wang, Qi；Han, Xiaoyi；Wang, Qixuan；Du, Minlong；Lei, Xinyue；Ge, Jiahao；Zhong, Rong；Wan, Chenxi；Gao, Xiaoli;Yang, Pu；Gao, Jinfeng
EUROPEAN JOURNAL OF AGRONOMY
DOI：10.1016/j.eja.2026.128029
Abstract
Continuous cropping disrupts farmland ecosystems, leading to aggravated soil-borne diseases and substantial crop yield losses. Soil amendments are considered promising strategies to alleviate continuous cropping obstacles. However, the effects of chemical fertilizers combined with organic manure and biochar amendments on soil water content (SWC), soil nitrogen pool levels, plant physiological traits, yield, and resource utilization efficiency in continuous common buckwheat cropping systems remain poorly understood. To address this knowledge gap, we conducted a four-year (2022-2025) field positioning experiment on the Loess Plateau with a completely randomized design including five treatments with four replicates: (a) no fertilizer (CK), (b) chemical fertilizers (NPK: 180 kg ha-1 N, 75 kg ha-1 P2O5, and 37.5 kg ha-1 K2O), (c) chemical fertilizers combined with organic manure (NPKM: 180 kg ha-1 N, 75 kg ha-1 P2O5, 37.5 kg ha-1 K2O, and 22500 kg ha-1 organic manure), (d) chemical fertilizers combined with biochar (NPKB: 180 kg ha-1 N, 75 kg ha-1 P2O5, 37.5 kg ha-1 K2O, and 10000 kg ha-1 biochar), and (e) chemical fertilizers combined with organic manure and biochar (NPKMB: 180 kg ha-1 N, 75 kg ha-1 P2O5, 37.5 kg ha-1 K2O, 11250 kg ha-1 organic manure, and 5000 kg ha-1 biochar). Results showed that compared to other treatments, NPKMB elevated SWC in the 0-100 cm soil layer (9.66-67.16 %) and increased total nitrogen (TN) (7.95-209.13 %) and alkali-hydrolyzable nitrogen (AN) (4.84-187.41 %) contents, thus creating a suitable soil environment for common buckwheat growth under continuous cropping stress. Meanwhile, NPKMB significantly enhanced the activities of root superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) by 3.47-45.31 %, 1.04-63.29 %, and 2.15-78.84 %, respectively, while increasing the contents of root proline, soluble sugar, and soluble protein by 6.90-83.67 %, 7.13-75.04 %, and 4.04-110.93 %, delaying root senescence and facilitating water and nitrogen absorption. Additionally, NPKMB improved leaf net photosynthetic rate (Pn, 9.78-95.52 %), stomatal conductance (Gs, 5.90-112.36 %), transpiration rate (Tr, 6.66-62.28 %), and chlorophyll content (SPAD value, 6.51-25.76 %), thereby promoting crop growth. Consequently, after three years of continuous cropping, NPKMB effectively alleviated growth constraints, achieving the highest dry matter weight (29.25 g plant-1), grain yield (1082.65 kg ha-1), N uptake (99.49 kg ha-1), and water use efficiency (WUE, 5.77 kg ha-1 mm-1). Overall, NPKMB fertilization strategy alleviated continuous cropping growth constraints of common buckwheat induced by long-term chemical fertilization via optimizing soil water-nitrogen environment, regulating plant physiological characteristics, and enhancing yield and resource absorption. These findings provide practical technical guidance for addressing continuous common buckwheat cropping challenges in rain-fed areas of the Loess Plateau amid global agricultural intensification.