碳酸氢根与水肥同层对玉米幼苗生长和吸收养分的影响

把水分(NaHCO3溶液或纯水)供应于底施了铵态或硝态N肥的土层内,以研究HCO3-及水肥供应方式对石灰性土壤上玉米生长及养分吸收的影响。结果表明,在限制灌水量的条件下,在土壤上层供应HCO3-显著抑制根系生长,但在下层供应对生长无明显影响;当施用不同形态N素时,HCO3-对N素吸收并无明显影响;此外,供应HCO3-溶液能明显提高灌水土层的土壤pH。总体来看,在供试条件下,HCO3-对玉米幼苗生长量、根系分布及养分吸收量的影响均较为有限,而后三者主要受施肥灌水层次的影响,即:在土壤上层施肥灌水,幼苗生长量显著降低;而在下层施肥灌水是一种节水节肥的水肥供应方式。但下层施肥灌水不利于植株的直立性。因为下层施肥灌水时根系主要分布在下层,在上层分布数量极少;而上层施肥灌水根系在上下两层中的分布无明显差异;下层施肥灌水的玉米植株,其N、P、K吸收量远高于上层施肥灌水的植株。

Effects of bicarbonate with identical layer of water and fertilization at the same soil zone on growth and nutrient uptake of maize plants

Although bicarbonate has been regarded as a major causal factor to affect yield and nutrient uptake of plants growing in the alkaline soils of arid and semiarid regions,little information is available on effects of bicarbonate on growth and N,P,K uptake of cereal crops growing on upland calcareous soils.A pot experiment using calcareous soil with 4.9% CaCO_3 was conducted to elucidate the effects of HCO~-_3 ions and application location of water and fertilizer on growth of maize(Zea Mays L.),water(15 mmol/L NaHCO_3 solution or distilled water) was irrigated in the soil layers through the injection apparatus and fine glass tube at the same soil zones as fertilization,in which nitrate N or ammonium N had been basally applied.The results indicated that,under the condition of deficit irrigation,supplying HCO~-_3 solution at the topsoil significantly inhibited the growth of roots,however,there was no obvious influence on growth when HCO~-_3 solution was supplied at the subsoil.For ammonium N or nitrate N applied,HCO~-_3 did not obviously affect N uptake;in addition,HCO~-_3 increased soil pH in layer where HCO~-_3 was supplied.Generally,under the experimental conditions,the effects of bicarbonate on growth increment of maize seedlings,root distribution and nutrient uptake were relatively rather limited,while they were mainly determined by layers of irrigation and fertilization as follows: Fertilizer and water applied at the topsoil would significantly raise the yield of maize,in the meantime,the maize plants grew normally when fertilization and irrigation occurred at the subsoil.This indicated that supplying fertilizer and water at the subsoil was a water-saving and fertilizer-saving measure.Irrigating and fertilization at the subsoil greatly stimulated the development and distribution of maize roots,but it easily result in the crop lodging because the roots was mainly distributed in the subsoil and roots in the topsoil were sparse.But there was no big difference on the root distribution between the topsoil and subsoil if the fertilization and irrigation occurred at the topsoil.Location of irrigation and fertilization also strongly influenced maize plant N,P, and K uptake comparing with that in the topsoil,irrigated and fertilized in the subsoil significantly increased the uptake of these three elements because the soil moisture regime was better if irrigation occured in subsoil.It also increased maize yield.