长期水稻-冬油菜轮作模式下钾肥的适宜用量

Optimum Amount of Potassium Fertilizer Applied under Continuous Ricerapeseed Rotation

研究长期施用钾肥对水稻-冬油菜轮作系统作物生产力、钾肥利用率和土壤供钾能力的影响,为水旱轮作区钾肥的统筹分配提供科学依据。2011—2016年在湖北省粮油主要生产区江汉平原布置中稻-冬油菜轮作定位田间试验。共设5个钾肥用量处理,分别为0 kg hm^(-2)(K0),45 kg hm^(-2)(K1),90 kg hm^(-2)(K2),135 kg hm^(-2)(K3)和180 kg hm^(-2)(K4),其中K2处理为当地测土配方推荐钾肥用量(K2O 90 kg hm^(-2))。在土壤供钾能力较高情况下,水稻和油菜年均产量分别为6.87 t hm^(-2)和2.25 t hm^(-2),经过一个轮作周期后施用钾肥具有明显的增产效果,且冬油菜季的产量和地上部吸钾量增幅最为明显,分别为16.9%和63.8%。长期施用推荐钾肥用量后,水稻和冬油菜的钾肥农学利用率年均分别为5.1kg kg–1和3.2 kg kg–1,而钾肥吸收利用率和钾肥贡献率水稻季明显低于冬油菜,这表明水稻吸收的钾素主要来自土壤,而冬油菜则需要较多的外源钾来满足自身对养分的需求。通过线性加平台肥效模型拟合得出,水稻季适宜钾肥用量为70.5~100.9 kg hm^(-2),平均96.6 kg hm^(-2),比推荐用量提高了7.3%;冬油菜季适宜钾肥用量为75.6~118.2 kg hm^(-2),平均107.0 kg hm^(-2),比推荐用量提高18.9%,且冬油菜对钾肥需求高于水稻。因此,在本试验条件下,长期施用年均推荐钾肥用量(180 kg hm^(-2))不仅影响作物产量的稳定性,还导致轮作系统钾素持续亏缺和土壤有效钾含量降低,故钾肥应优先施用于油菜季并且重视作物秸秆还田、归还秸秆钾素,以维持农田钾素平衡和生产力可持续性。

In order to provide a scientific basis for K fertilization in paddy-upland rotation,effects of K fertilizer rate on cropproduction,K efficiency,and soil K status were studied.A long-term(2011–2016)field experiment was conducted in the JianghanPlain,Hubei province,China.Five treatments were applied with three replications each:0kg ha–1(K0),45kg ha–1(K1),90kgha–1(K2),135kg ha–1(K3)and180kg ha–1(K4),where K2treatment was the recommended amount of K fertilizer(90kg ha–1).The yields of rice and rapeseed were6.87t ha–1and2.25t ha–1respectively,in the condition without K fertilizer and with highersoil available K content.Application of K fertilizer could significantly increase the yield after one crop rotation;the increase inrapeseed season was higher than that in the rice season,accounting for16.9%and63.8%,respectively.With the application of therecommended amount of K fertilizer,the agronomic K efficiency(KAE)of rice and rapeseed was5.1kg kg–1and3.2kg kg–1,respectively;however,the K recovery efficiency(KRE)and K contribution rate(KCR)of rice were lower than those of rapeseed,which indicated that K absorbed by rice was mainly from the soil,and more external supply of K fertilizer was needed to meet the nutrient demand of rapeseed.According to the fertilizer efficiency model,the optimum annual amounts of K fertilizer(K2O)were70.5–100.9kg ha–1for rice,with an average of96.6kg ha–1,and75.6–118.2kg ha–1for rapeseed,with an average of107.0kg ha–1,which were7.3%and18.9%higher,respectively,than the recommended amount in this region.Under the soil K condition in thisstudy,long-term application of recommended K fertilizer rate(180kg ha–1per year)could not only affect yield stability,but alsodecrease crop system K balance and soil available K content.Therefore,K fertilizer should be preferentially applied in the rapeseedseason rather than the rice season and straw returning to field should also be taken into consideration to maintain the soil Kbalance and sustainable high-yield production in the crop rotation system.