施氮量对南方甜玉米钾素吸收利用的影响

【目的】 探明南方鲜食玉米区高产条件下施氮量对甜玉米钾素吸收利用及其转运规律的影响。 【方法】 选用国审甜玉米品种粤甜16为供试材料，设置7个施氮量处理 (N 0、100、150、200、250、300、450 kg/hm2)，连续进行2年的大田试验 (2015—2016年)。在雄穗开花期和乳熟收获期测定甜玉米植株及各器官干重、钾养分含量，研究分次施肥条件下，不同施氮量对甜玉米乳熟收获期植株体内的钾养分吸收积累与分配比例、钾收获指数和效率，以及对花后钾素同化积累和转运的影响。 【结果】 在2个生长季，施氮量均显著影响甜玉米植株体内的钾素吸收量。在低于N250水平时，不同施氮量处理之间的钾素吸收量差异主要是由单位面积干物质生产量不同和植株钾浓度不同所引起；在高于N250水平时，不同施氮量处理之间的钾素吸收量差异主要是由单位面积干物质生产量不同所引起。随着施氮量增加 (0～450 kg/hm2)，地上部干物质生产量、钾素吸收量均呈现上升的趋势。在施氮量0～250 kg/hm2之间，鲜穗产量、穗钾素含量、钾素收获指数随着施氮量增加呈现上升的趋势，在施氮量250～450 kg/hm2之间，鲜穗产量、穗钾素含量呈现平稳略波动的趋势，钾素收获指数呈现下降的趋势；随着施氮量增加 (0～450 kg/hm2)，生产单位鲜穗所需的钾素量呈现先下降后略微波动的趋势。当施氮量高于250 kg/hm2时，植株对钾素的吸收积累量增加，但主要是茎鞘叶部分，穗部的吸收量并没有明显增加。施氮量显著影响花后根系同化吸收、茎鞘转运和叶片转运对穗的钾贡献，在一定范围内 (低于N 250 kg/hm2)，增施氮肥可以提高茎鞘、叶片对穗钾的花后转运量，随着施氮量增大 (高于250 kg/hm2)，茎鞘、叶片钾的转运量不再增加，在施N 250 kg/hm2 时，茎鞘、叶片的钾素转运量达到峰值，粤甜16的穗钾来自花后茎鞘转运、叶转运、花后氮同化的贡献率分别为 34.1%、30.8%、35.1%。 【结论】 采用多次施肥，不同施氮量对甜玉米植株的钾素吸收积累的影响呈现阶段性差异；在N 250 kg/hm2时，鲜穗产量和钾素的吸收利用率均较高，从而实现高产与养分高效利用的协调统一。

Effects of nitrogen application on potassium uptake and utilization of sweet corn in south China

【Objectives】 Characteristics of potassium (K) uptake, utilization and transformation of sweet corn were studied for both high quality and high yield. 【Methods】 Field experiments with a sweet corn cultivar (Zea mays L. saccharata sturt) ‘Yuetian 16’ (YT16) were conducted in 2015 and 2016. Seven nitrogen fertilizer rates were designed as N 0, 100, 150, 200, 250, 300, and 450 kg/hm2, and using randomized complete block design with 3 replications. Aboveground plants were sampled to measure the dry matter weight, K content, K uptake, K harvest index and K use efficiency at flowering and milk-ripe harvest stages. 【Results】 Significant differences in plant K uptake at milk-ripe harvest stage were found among 7 fertilizer N application rates. Under N 250 kg/hm2, the differences of plant K uptake among the N rates were mainly due to the differences of the dry matter production and K content, and above N 250 kg/hm2, the differences of plant K uptake among the N rates were mainly due to the differences of dry matter production. When the N application rates were increased from 0 to 250 kg/hm2, the fresh ear yield, K uptake of ear, and the harvest index of K showed an increasing tendency. When the N application rates were in range of 0–450 kg/hm2, both the dry matter production and plant K uptake were increased with the increase of N application rate. While with the increase of N application rate from 250–450 kg/hm2, the fresh ear yield and K content of ear were kept stable, and the K harvest index showed a decreasing tendency. With the increase of N application rate (0?450 kg/hm2), K requirement for producing 1000 kg of fresh ear yield was decreased firstly and then fluctuated. Above N rate of 250 kg/hm2, both the K uptake and accumulation were increased, and the increase was mainly found in stem, sheath and leaf. N application rates significantly influenced the contribution of the K assimilated in roots and transformed from stem sheath and leaf after flowering to the ear potassium. The increase of N rate would not stop improving the transformation of K from stem sheath and leaf to potassium capacity of ear after flowering until the N rate was higher than 250 kg/hm2. Under the N rate of 250 kg/hm2, the K transformation from stem sheath, and leaf to ear would reach the peak, and the contribution rates to ear K from transformation of stem sheath, leaf and assimilation of root after flowering were 34.1%, 30.8% and 35.1%, respectively. 【Conclusions】 N application rates significantly affect plant K uptake of sweet corn in the range of N application rate of 0?450 kg/hm2. Higher N inputs will stimulate the plant K uptake and transformation from vegetable organs to ears within the N range of 0?250 kg/hm2, while the transformation will not increase when the N rate is in the range of 250?450 kg/hm2, the fresh ear yield will not keep increasing, and the K use efficiency will be fluctuated as a result . Therefore, N application rate of 250 kg/hm2 could be thought reasonable from the point of view of K use efficiency for sweet corn.