施氮量对稻茬小麦秸秆干物质和养分垂直分布的影响

为给秸秆资源合理开发利用提供依据,以弱筋小麦品种宁麦9号和强筋小麦品种豫麦34为材料,研究了不同施氮水平(0、75、150、225、300kg·hm-2)下成熟期小麦植株干物质、氮、磷和钾的积累垂直分布特点。结果表明,小麦籽粒产量随施氮量增加呈先增后降的趋势,以施氮225kg·hm-2处理的产量最高。小麦冠层干物质和养分存在明显的垂直梯度,增加施氮量显著提高了冠层各层次干物质、氮、磷和钾素的积累量。随冠层层次的降低,叶片干物质积累量先降后增,氮、磷积累量降低,钾积累量升高。茎鞘干物质和钾素积累量则随冠层层次的降低而升高,氮、磷积累量先增后降,以倒2、倒3层较高。各叶层、茎鞘层干物质、氮、磷、钾积累量与籽粒产量均呈极显著正相关关系。在施氮225kg·hm-2处理下,小麦秸秆全量还田对土壤氮、磷、钾养分的贡献分别为3.7、2.8、9.9kg·hm-2;留茬15cm时,残茬干物质、氮、磷、钾还田量占整株秸秆量的比例分别为40%、50%和40%左右。

Effects of Nitrogen Rates on Vertical Distribution of Dry Matter and Nutrient of Winter Wheat in Rice-Wheat Rotation

It is very important to elucidate the collectable amounts and the nutrient status in different layers of wheat canopy to better utilize wheat straw. In this study, by using two wheat cultivars(Triticum aestivum L. cv Ninmai 9 & cv Yumai 34), field experiments with five treatments(nitrogen rate of 0, 75, 150, 225 and 300 kg·hm^-2) were conducted in Nanjing during 2011 and 2012. The experiment was designed as a randomized complete block using three replications and each replication was sampled at maturity. After cutting off the spike, the plant shoots were divided into four sections averagely to investigate the vertical distribution of dry matter, nitrogen(N), phosphorus(P) and potassium(K) in different positions of the wheat canopy, and each section was separated into leaves and culms. The results showed that the grain yield reached the highest in the treatment 225 kg·hm^-2. There were significant vertical differences on dry matter and nutrient accumulation in the wheat canopy layers from top to root. The total accumulation amount of dry matter, N, P and K in the straw increased with the increasing of nitrogen rate. In each treatment, the dry matter weight increased firstly and decreased afterwards in the four layers of the wheat canopy from top to root, N and P accumulation decreased, while K accumulation increased. And in the stem-sheath, dry matter and K accumulation increased, and N and P accumulation reached the highest in the second and the third layer. There were significant linear relationships between grain yield and the accumulation of dry matter, N, P and K in different layers of leaf and sheath. The results indicated that in the highest grain yield case, when the wheat straw was returned to the field totally, the contributions of N, P and K in wheat straw to that in soil pool were 3.7, 2.8 and 9.9 kg·hm^-2, respectively, and when only the straw stubble(leaf and stem-sheath in the fourth layer + glume) was returned to the field, the proportions of returned to the total in straw were 40, 50 and 40%, respectively.