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Introduction Previous studies have shown that straw returning combined with potassium (K) fertilization improves grain yield and K use efficiency (KUE) in transplanted rice. However, in rice–wheat rotation systems, the synergistic effects of wheat-straw returning and optimized K fertilization on yield, rice quality, and KUE of direct-seeded rice remain poorly understood. In particular, the relationships among photosynthetic material production, source–sink coordination, and K balance, in relation to grain yield and rice quality, have not been clearly elucidated. Methods A two-factor field experiment was conducted using super hybrid indica rice Fyou 498 to investigate the combined effects of wheat-straw management and K fertilization on yield, rice quality, and KUE in mechanically direct-seeded rice. Two straw treatments were set: no wheat-straw returning (M 0 ) and wheat-straw returning (M 1 ), with each straw treatment crossed with five elemental K application rates: 0, 62.5, 125, 187.5, and 250 kg K ha -1 . Results Wheat-straw returning showed a statistically significant effect. Compared with M 0 , M 1 significantly increased the photosynthetic potential from jointing to full heading by 1.83%–22.34%, improved postheading dry matter accumulation by 2.06%–36.56%, and increased yield by 1.06%–14.36%. Under M 1 combined with 125 kg K ha -1 , dry matter accumulation increased by 9.76%–86.53%, K translocation amount and contribution rate stem sheath (leaf) increased by 0.78%–38.34%, yield improved by 4.79%–19.95%, KUE increased by 3.61–15.15 kg kg -1 , grain chalkiness reduced by 0.03%–2.97%, taste value increased by 0.64–5.14, and soil K depletion was reduced by 39.25–52.13 kg ha -1 . Notably, correlation analysis showed that an increase in the contribution rate of K translocation from the stem sheath from full heading to maturity ( r = 0.50 * –0.96 ** ) is a key pathway for achieving synergistic high yield, high quality, and high KUE in direct-seeded rice under combined wheat-straw returning and K fertilizer application. Discussion This optimized management strategy of wheat-straw incorporation (fresh straw incorporation rate: 5,050–5,440 kg ha -1 , straw moisture content: 28.9%–30.1%) combined with 125 kg K ha -1 represents a promising approach for sustaining rice production in rice–wheat rotation systems under humid subtropical monsoon pedoclimatic conditions, delivering synergistic improvements in grain yield, rice quality, resource-use efficiency, and economic benefits for mechanically direct-seeded rice.
Sun et al. (Wed,) studied this question.