N-K Management in Machine-Transplanted Rice Effects of N-K management strategies on nutrient uptake efficiency, lodging resistance, and yield in machine-transplanted rice

Zhixin LiMingMing HuTao LiuYuan TangRuhongji LiuZhenbo PengCheng WangZhenlan PengZhonglin WangZongkui ChenZhiyuan YangYong-jian SunJun Ma^*

• 四川农业大学成都校区, 成都市, China

Introduction: Imbalanced N-K ratios reduce nutrient uptake efficiency while elevating lodging susceptibility, thereby destabilizing yield potential. Optimizing N-K ratios is therefore crucial for enhancing nutrient efficiency, lodging resistance, and yield potential. Methods: This study employed the hybrid indica rice cultivar F-you 498 as experimental material. Two K management strategies (basal:panicle = 10:0 and 5:5, denoted as K1 and K2) and three N application regimes (basal:tiller:panicle = 7:3:0, 5:3:2, and 3:3:4, denoted as N1, N2, and N3) were established. Both fertilizers were applied at identical total rates of 150 kg ha-1 for N and K, to investigate N-K interactions on rice growth and nutrient utilization. Results: N-K interactive effects on dry matter accumulation, nutrient uptake, lodging resistance, and yield. Split potassium application (K2) increased grain yield by 3.06% over basal-only application (K1), with higher productive panicles, spikelets per panicle, total spikelets, and seed-setting rate. K2 enhanced post-heading dry matter translocation and improved N-K uptake, elevating panicle N and K accumulation by 5.01% and 13.70%, respectively. Furthermore, K2 significantly enhanced lodging resistance. Under K2, the N3 treatment increased yield by enhancing the number of effective panicles, grains per panicle, and total spikelets, with average yield increases of 12.17% and 4.77% over N1 and N2, respectively. Post-heading dry matter accumulation, remobilization ratio, and contribution rate in N3 were higher than in N1 and N2, with two-year average increases of 25.54%, 5.37%, and 7.42% over N1 and 12.68%, 2.76%, and 2.57% over N2. N3 also promoted the translocation of N and K. Compared to N1 and N2, N3 increased whole-plant N translocation and N transferred to the panicle by 38.09%, 27.45% and 14.53%, 12.45%, respectively; whole-plant K translocation and K transferred to the panicle increased by 11.46%, 28.26% and 13.35%, 18.35%, respectively. Additionally, N3 improved lodging resistance by thickening internodes and stem-N-K Management in Machine-Transplanted Rice sheath walls, and the lodging index was significantly negatively correlated with N and K accumulation in stem-sheaths. Discussion: Overall, the K2N3 combination enhances post-heading assimilate allocation and nutrient translocation in machine-transplanted rice, strengthens stem mechanical properties, optimizes panicle traits, and ultimately achieves stable and high yields.