Potassium (K) is not easily assimilated into organic matter but helps to improve rice quality. Paddy yield and its quality depend on the correct time of fertilization and harvesting (days after flowering) in the field. Changes in the grain quality of (Oryza sativa L.) were studied in a field experiment over two dry seasons using three rates of muriate of potash (MOP; 60% K2O) as 12.5, 25 and 37.5 kg/ha applied at the time of heading (7 weeks after planting—WAP). Paddy samples were harvested during 25, 30 (control), 35 and 40 days after 50% flowering (DAFF). Grain yield and physico-chemical characteristics of grain were studied after harvesting. The impact of seasons and treatments’ interactions was not statistically significant (P > 0.05) and, hence, data were averaged over two seasons. Length, breadth, true density and bulk density of rice grains were the highest with 37.5 kg MOP/ha applied at heading and harvested at 30–35 DAFF. Crude protein (6.24%) and crude fat (2.61%) contents in grains were the highest when harvested at 40 DAFF and 35–40 DAFF, respectively. Amylose content decreased with increased MOP rates at the time of heading and delayed paddy harvest. The highest average paddy yield (APY; 6.85 t/ha), head rice yield (HRY; 65%) and total rice milling yield (TMY; 67%) were recorded with 37.5 kg MOP/ha applied at heading of rice plant and paddy harvested at 35 DAFF. The APY, HRY and TMY were also 13.8, 7.7 and 5.9% higher, respectively, compared to the control. Applying K fertilizer at a rate 50% more (18.75 kg K/ha) than the recommended rate at the time of heading (7 WAP) and harvesting paddy at optimum maturity (35 DAFF), which is 5 days later than the recommendation, increase the yield and grain quality of direct seeded rice. Harvesting later than 35 DAFF resulted in a 10.5% loss of HRY (P < 0.05). The present study showed that K fertilizer applied at the rate of 37.5 kg MOP/ha at the time of heading 50% higher than the recommended rate is the best among K fertilizer treatments to obtain the highest HRY.

中文翻译：

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抽穗时钾肥用量的增加可提高直播稻的品质

钾（K）不易被有机物吸收，但有助于改善稻米质量。稻田的产量及其质量取决于田间施肥和收获（开花后的天数）的正确时间。（Oryza sativa L.）的谷物品质在两个干旱季节的田间试验中进行了研究，使用了三种钾肥（MOP； 60％K2O）的三种比率，分别为12.5、25和37.5 kg / ha。抽穗（播种后7周-WAP）。50％开花（DAFF）后25、30（对照），35和40天收获稻田样品。收获后研究了籽粒的产量和理化特性。季节和处理间相互作用的影响在统计学上不显着（P> 0.05），因此，将两个季节的数据进行平均。长度，宽度 抽穗时施用37.5 kg MOP / ha，并在30-35 DAFF收获时，稻谷的真实密度和堆积密度最高。当分别以40 DAFF和35-40 DAFF收获时，谷物中的粗蛋白（6.24％）和粗脂肪（2.61％）含量最高。抽穗和收割稻谷时，直链淀粉含量随MOP速率的增加而降低。水稻和稻谷抽穗施施37.5 kg MOP / ha的最高平均水稻产量（APY； 6.85吨/公顷），糙米产量（HRY； 65％）和碾米总产量（TMY； 67％）最高。在35 DAFF收获。与对照组相比，APY，HRY和TMY分别也分别高13.8％，7.7％和5.9％。抽穗时（7 WAP）施用的钾肥的比例比建议的施用量高出50％（18.75 kg K / ha），并以最佳成熟度（35 DAFF）收获水稻 比建议的时间晚5天，可以提高直播稻的产量和谷物品质。收获晚于35 DAFF会导致HRY损失10.5％（P <0.05）。目前的研究表明，钾肥以37.5 kg MOP / ha的比例施用时，比推荐的施用量高出50％，这是获得最高HRY的K肥料中最好的。