水旱轮作条件下不同类型土壤供钾能力及钾素动态变化研究

POTASSIUM SUPPLY CAPACITY OF AND POTASSIUM DYNAMICS IN DIFFERENT TYPES OF SOILS UNDER PADDY RICE-RYEGRASS ROTATION

采用盆栽试验,研究了黑麦草-水稻轮作条件下不同类型土壤供钾能力及钾素动态变化,以期为土壤供钾机制研究及合理的钾素调控提供依据。结果表明:不施钾条件下(NP处理),潮土上种植作物的生物量和吸钾量最高,黄褐土次之,红壤最低;施钾条件下(NPK处理),3种土壤上种植作物的生物量无显著差异,作物吸钾量为黄褐土>潮土>红壤。整个轮作期,红壤、黄褐土和潮土NPK处理的作物生物量较NP处理分别增加55.6%、45.2%和23.2%,作物吸钾量分别增加368.8%、166.8%和74.5%。轮作前季(黑麦草季),NP处理的3种土壤水溶性钾含量和交换性钾含量均降低,潮土非交换性钾含量明显降低,红壤和黄褐土非交换性钾含量在前期变化不大,中期有升高的趋势,后期显著降低;NPK处理的土壤钾含量均高于NP处理,且各种形态钾含量的变化趋势与NP处理基本相同。轮作后季(水稻季),NP处理的3种土壤水溶性钾含量变化不大,交换性钾含量呈先降低后升高的趋势,非交换性钾含量呈先升高后降低的趋势;NPK处理的土壤交换性钾含量在水稻生长前期明显升高,中期下降,后期有略微上升,水溶性钾和非交换性钾含量有先升高后降低的变化趋势。综上所述,在不施钾条件下,轮作期内各土壤钾素消耗量较大,水溶性钾和交换性钾含量降低,并促进了非交换性钾的释放;施钾能提高土壤水溶性钾和交换性钾含量,并向非交换性钾方向转化,施钾对黑麦草和水稻有显著增产效果,可以有效地提高土壤供钾水平。

A pot experiment was carried out using different types of soils to study their potassium （K） supply capacities and K dynamics under a ryegrass-rice rotation system, with a view to providing scientific basis for the research on mechanism of soil supplying K and reasonable K control. Results show that both aboveground biomass and K uptake of the crops in the group without K treatment （NP） were the highest in fluvo-aquic soil （FS）, which was followed by yellow cinnamon soil （ YCS）, then red soil （RS） , while in the group with K, fertilization, no significant difference （p 〉 0.05 ） between the soils was observed in aboveground biomass and a decreasing order of YCS 〉 FS 〉 RS was in terms of K uptake. Treatment NPK was 55.6% , 45.2% and 23.2% higher than treatment NP for red soil, yellow cinnamon soil and fluvoaquic soil, respectively, in biomass and 368.8% , 166.8% and 74.5% , higher, respectively in K uptake. In the ryegrass growth season, the concentrations of water soluble K and exchangeable K in treatment NP decreased in all the soils. The concentration of non-exchangeable K decreased significantly in fluvo-aquie, but remained almost unchanged in the early season, rose in the middle season and dropped in the late season in yellow cinnamon soil and red soil. Soil K was much higher in treatment NPK than in treatment NP, but varied in a similar pattern in all the three soils, regardless of treatments and K forms. During the rice growing period, in treatment NP, water soluble K in all the soils did not change much soil exchangeable K declined first and then rose, but non-exchangeable K showed a reverse trend, while in treatment NPK, soil exchangeable K rose significantly in the early, and declined in the middle and then turned slightly back again in the late period, whereas soil water soluble K and non-exchangeable K showed a rising and then failing trend. To sum up, In treatment NP, K consumption was higher in all the soils and in all the periods of the rotation, thus decreasing both soil water soluble K and exchangeable K and in turn triggering release of non-exchangeable K. Application of K fertilizer increases the concentrations of water soluble K and exchangeable K and the ratio of K transformed into non-exchangeable K, thus effectively improving K supply capacity of the soil, and eventually increasing the yield of ryegrass and rice signifi- cantly.