Soil Science Division, Nepal Agricultural Research Council, Khumaltar, Lalitpur, Nepal.
Department of Biosystems Engineering and Soil Science, University of Tennessee-Knoxville, Knoxville, TN, United States of America.
PLoS One. 2021 Mar 18;16(3):e0248837. doi: 10.1371/journal.pone.0248837. eCollection 2021.
Most of the soils of Nepal had a higher potassium (K, expressed as K2O) level inherently. Later in 1976, the Government of Nepal has recommended K fertilizer rate at 30 kg K2O ha-1 in rice-wheat cropping systems. However, those crops began showing K deficiency symptoms in recent decades, which could be due to a large portion of soils with depleted K level or the insufficient input of K fertilizer for crop production. This study explored a limitation of K nutrient in the crops by establishing field trials from 2009-2014 at three agro-ecozones i.e., inner-Terai (2009-2010), high-Hills (2011-2012), and Terai (2012-2014) in Nepal. Seven rates of K fertilizer at 0, 15, 30, 45, 60, 75, and 90 kg K2O ha-1 were replicated four times in a randomized complete block design, where crop yields and yield-attributing parameters of rice-wheat cropping system were recorded. Results revealed that an increase in K rates from 45 to 75 kg K2O ha-1 under inner-Terai and Terai conditions and 45 to 60 kg ha-1 under high-Hills conditions produced significantly higher grain yields compared to the recommended K dose. Economically, the optimum rate of K fertilizer should not exceed 68 kg K2O ha-1 for rice in all agro-ecozones, or 73 kg K2O ha-1 for wheat in inner-Terai and 60 kg K2O ha-1 for wheat in high-Hills and Terai. Our findings suggest to increase potassium application in between 1.5 to 2.5 times of the current K fertilizer rate in rice-wheat cropping system of Nepal that need to be tested further in different locations and crop varieties.
尼泊尔的大部分土壤本身就具有较高的钾（K，以 K2O 表示）含量。后来在 1976 年，尼泊尔政府建议在水稻-小麦轮作系统中每公顷施用 30 公斤 K2O 的 K 肥。然而，近几十年来，这些作物开始出现 K 缺乏症，这可能是由于大部分土壤的 K 含量下降，或者作物生产中 K 肥的投入不足。本研究通过 2009-2014 年在尼泊尔三个农业生态区（内特莱 2009-2010 年、高山区 2011-2012 年和特莱 2012-2014 年）建立田间试验，探讨了作物中 K 养分的限制。在随机完全区组设计中，7 个 K 肥用量（0、15、30、45、60、75 和 90 kg K2O ha-1）重复 4 次，记录了水稻-小麦轮作系统的作物产量和产量构成参数。结果表明，在内特莱和特莱地区，K 肥用量从 45 增加到 75 kg K2O ha-1，高山区从 45 增加到 60 kg K2O ha-1，与推荐的 K 用量相比，稻谷产量显著提高。从经济角度来看，在所有农业生态区，水稻的最佳 K 肥用量不应超过 68 kg K2O ha-1，内特莱的小麦不应超过 73 kg K2O ha-1，高山区和特莱的小麦不应超过 60 kg K2O ha-1。我们的研究结果表明，需要在不同的地点和作物品种中进一步测试，在尼泊尔的水稻-小麦轮作系统中，钾的施用量应增加到目前 K 肥用量的 1.5 到 2.5 倍。
