Effects of nitrogen fertilizer varieties and nitrogen application rate on root characters and growth of maize seedlings under root-zone fertilization
The nutrient concentration around root-zone is high under the condition of root-zone fertilization(RZF),and the absorption and utilization of nutrients by roots would be further improved,but the maize root is relatively fragile at seedling stage,so exploring the response of maize root system at seedling stage to root-zone fertilization(RZF)of nitrogen(N)is conducive to achieve high yield and use efficiency.A pot experiment was conducted to study the characteristics and distribution of maize root system at seedling stage under RZF of N,and to develop the theory of RZF and provide theoretical basis for precision fertilization of maize.Two N fertilizer varieties(urea and controlled-release urea,marked as U and CRU,respectively)and four N application rates(N 90,135,180,225 kg/hm2)were conducted to study the effects of N fertilizer varieties and N application on the root morphology and distribution of maize seedlings under RZF.The results showed that there were no significant differences among all treatments after 10 d after transplanting.After 25 d of transplanting,the root indices(root biomass,total root length,total surface area,total volume,average diameter,root activity)of U treatments under RZF were increased first and then decreased with the increase of N rate.However,the root indices of RZF with CRU increased or kept stable with the increased N rate.Compared with CK,the root biomass(25.41%and 64.37%),total root length(40.14%and 53.45%),total root surface area(30.50%and 32.52%),total root volume(55.94%and 46.72%),average diameter(20.01%and 23.18%)and root activity(49.44%and 50.64%)of UR135 and CRUR225 were significantly increased,while those of UR225 were significantly decreased.The root biomass of different soil layers was also affected by N fertilizer variety and N application.The root biomass of 0-5 and 5-10 cm soil layers ranked as:CRUR225≥CRUR180=UR135≥CRUR135>UR90=UR180=CRUR90>CK>UR225,the 0-5 and 5-10 cm soil layers of CRUR225 were significantly increased by 61.44%and 69.79%,respectively,compared with CK,while the root biomass of UR225 was significantly decreased by 45.66%and 36.01%respectively.The aboveground indices(leaf length,leaf width,stem diameter,plant height,SPAD and aboveground biomass)of U application in root zone were increased first and then decreased with the increase of N application.Compared with CK,the leaf length,leaf width,stem diameter and plant height of UR135 and CRUR225 were significantly increased by 44.86%and 40.85%,47.59%and 59.42%,34.38%and 63.13%,43.55%and 55.32%,respectively,while the stem diameter and plant height of UR225 were reduced by 4.69%and 3.17%respectively.In conclusion,U treatment promoted maize root growth at low and middle N application level(N 90 and 135 kg/hm2),and inhibited root growth at high N application level(N 180 and 225 kg/hm2)under RZF.CRU in RZF is relatively safe,and different N rates can promote the growth of maize.Under RZF,when low and medium N rates are conducted,U or CRU can be selected,however,when high N rate is adopt,CRU is more suitable.
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NSTL
万方数据
维普
