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本文研究了石灰性土壤和低钾酸性土壤上由于尿素水解引起pH升高,产生NH_3对作物生长的影响,特别是对根系发育的有害作用。盆栽试验表明,石灰性土壤上表施尿素200ppmN后播种小麦,抑制了种子的生根和发芽。分蘖末期追施尿素200 ppmN,在10天中小麦根系干物质的积累量与对照相比反而有减少趋势,在低钾的酸性土壤上也观察到同样的现象。受尿素伤害的植株含钾低,并出现类似缺钾的症状。用一定量的NH_3处理植株,其体内K~+和游离氨基酸出现大量的外溢。气态NH_3为5微克/厘米~3时,水稻、小麦根系就出现明显的受害症状。在低浓度,短时间处理后取消NH_3的作用,则受害植株尚能恢复生长。尿素施入后盖土再播种,种、肥分隔条施以及尿素掺泥炭混施等措施都可防止NH_3逸失,减缓对作物根系的有害作用。
In this paper, the effects of ammonium nitrate on crop growth caused by urea hydrolysis in calcareous soil and low-potassium acid soil were studied, especially for root development. Pot experiments showed that on the calcareous soil, 200ppm N urea was applied to sow wheat and inhibited rooting and germination of the seeds. At the late tillering stage, urea 200 ppmN was topdressed, and the accumulation of dry matter in wheat roots tended to decrease compared with the control at the end of 10 days. The same phenomenon was observed in the low potassium acid soils. Plants that are injured by urea are low in potassium and show symptoms similar to potassium deficiency. With a certain amount of NH_3 plants, its body K ~ + and free amino acids appear a lot of spillover. Gaseous NH_3 of 5 μg / cm ~ 3, rice, wheat root symptoms appeared obvious damage. In the low concentration, short time after the abolition of the role of NH_3, the affected plants still able to resume growth. Covering soil after sowing with urea and then sowing, species, fertilizers, and the application of urea and mixed with peat and other measures can prevent the loss of NH_3, slowing the harmful effects of crop roots.