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% CaCO3 was conducted to elucidate the effects of HCO3- ions and application location of water and fertilizer on growth of maize(Zea Mays L.),water(15 mmol/L NaHCO3 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 HCO3- solution at the topsoil significantly inhibited the growth of roots,however,there was no obvious influence on growth when HCO3- solution was supplied at the subsoil.For ammonium N or nitrate N applied,HCO3- did not obviously affect N uptake;in addition,HCO3- increased soil pH in layer where HCO3- 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.