土壤pH对不同酸性敏感型水稻品种氮利用效率与根际土壤生物学特性的影响

为探讨酸化土壤影响水稻氮利用效率的土壤生物学机制,以酸性敏感型品种五优308和酸性特异型品种荆楚优148为材料,采用盆栽试验考察不同土壤pH条件下水稻的氮利用效率指标与根际土壤酶活性及微生物数量的关系。结果表明,在土壤pH值3.5~6.5范围内,五优308氮素稻谷生产效率(NGPE)与氮生理效率(NPE)随土壤pH值的下降显著降低,氮收获指数(NHI)变化不明显;而荆楚优148中3个指标在pH值5.0时最大。土壤pH值的下降均降低了2个品种的根际土壤酶活性,但品种间、时期间降幅稍有差异。五优308各时期磷脂脂肪酸(PLFA)含量随土壤pH值降低而降低,而荆楚优148各时期PLFA含量在pH值5.0时最高。五优308的NGPE、NPE与3种土壤酶活性均呈显著正相关,而NHI仅与蔗糖酶活性呈极显著正相关;荆楚优148氮利用效率指标与土壤酶活性呈负相关,与土壤蔗糖酶和脲酶活性的相关性较显著;五优308氮利用效率指标与微生物数量呈正相关,但其显著性在不同生育时期间与微生物间有一定差异;而荆楚优148氮利用效率指标与分蘖~孕穗期土壤微生物数量呈极显著正相关,与齐穗期土壤微生物数量呈极显著负相关。由此可见,酸性敏感型水稻品种氮利用效率随土壤pH下降显著降低,且主要由根际土壤酶活性与微生物数量显著下降所致;而酸性特异型水稻品种氮利用效率在pH值5.0时最大,且其与土壤生物学特性指标的相关性表现与酸性敏感型水稻品种不同。本研究初步明确了酸化稻田影响水稻氮利用效率的土壤生物学机制,为酸化稻田适宜水稻品种选择提供了参考。

Effect of Soil pH on Nitrogen Utilization Efficiency and Biological Characters of Rhizosphere Soil of Rice Varieties With Different Acid-sensitivity

In order to discuss the soil biological mechanism of nitrogen utilization efficiency of rice affected by acidified soil,the correlation between nitrogen utilization efficiency indexes of rice and enzyme activities and microbe quantity in rhizosphere soil under different soil pH was studied by pot experiment.Wuyou308,an acid-sensitive rice variety and Jingchuyou 148,an acid-special rice variety were selected as experimental materials.The results showed that nitrogen grain production efficiency (NGPE) and nitrogen physiological efficiency (NPE) of Wuyou 308 significantly decreased with the decline of soil pH in range of 6.5 to 3.5,while its nitrogen harvest index (NHI) changed inconspicuously,and three indexes of nitrogen utilization efficiency of Jingchuyou 148 reached the maximum when soil pH was 5.0.Enzyme activity in rhizosphere soil of two varieties decreased with the decline of soil pH,while there were differences in two varieties and among different stages.Content of phosphate fatty acid (PLFA) at all stages of Wuyou 308 decreased with the decrease of soil pH,while that of Jingchuyou 148 reached the maximum when soil pH was 5.0.There was a significantly positive correlation between NGPE and NPE of Wuyou308 and activities of three kinds of soil enzyme,and there was a very significantly positive correlation between NHI and invertase activity.As for Jingchuyou 148,there was negative correlation between nitrogen utilization efficiency indexes and soil enzyme activities,and significant correlation was found between nitrogen utilization efficiency and activities of invertase and urease.It was also found a positive correlation between nitrogen utilization efficiency indexes of Wuyou 308 and soil microbe quantity,while the significance showed different among different stages and microbes.As for Jingchuyou148,there was a very significantly positive correlation between nitrogen utilization efficiency indexes and soil microbe quantity at tillering to booting stage,while the very significantly negative correlation existed between nitrogen utilization efficiency and soil microbe quantity at full heading stage.These results indicated that nitrogen utilization efficiency of acid-sensitive rice variety significantly decreased with the decline of soil pH,which mainly deduced by significant decrease of soil enzyme activities and soil microbe quantity,while nitrogen utilization efficiency of acid-special rice variety reached the maximum at pH value 5.0,and its correlation between nitrogen utilization efficiency and soil biological character indexes showed very different between those of acid-sensitive rice variety.This study preliminarily confirmed the soil biological mechanism of nitrogen utilization efficiency of rice affected by acidified soil,and provided reference for screening suitable rice varieties in acidified paddy field.