| The distribution of precipitation is not consistent with the critical period of spring maize water demand at Weibei dry land.Water is the main factor limiting agricultural development in this area.The dry land maize in this area implements one-year ripening system,and there is a fallow period of 7 months after spring maize is harvested every year.Therefore,how to store the water during the rest period for maize growth has become the focus of research.At the same time,under the condition that the soil moisture is constant,how to imply more efficient comprehensive cultivation measures to achieve the combination of soil water storage and crop water use,improve the effective use of light,temperature,water and fertilizer resources by spring maize,and obtain higher yield and economic benefits is also the focus of research in this area.Therefore,in this study,the three-factor positioning experiment of tillage,nitrogen application,and density was carried out in Heyang County,Weibei dryland from 2018 to 2019.The experiment designed three tillage treatments:conventional tillage(CT),no-tillage(NT),and subsoil tillage(ST);three nitrogen application gradient:(N:0,150,225 kg/hm~2)and two planting densities(D:52500,67500plants/hm~2),analysis of soil moisture dynamics,spring maize growth,nutrient change,yield and the change law of its constituent factors provides a scientific basis for the selection of cultivation modes of high-efficiency water and fertilizer and yield and income in dryland maize.The main results of the study are as follows:(1)NT and ST soil increased soil water storage by 8.4%and 5.6%,and soil water evaporation decreased by 10.5%and 9.2%,respectively.In 2018,where there was more precipitation during the fallow period,there was no significant difference between NT and ST treatment,but in 2019,when there was less rainfall,NT treatment was more conducive to increasing soil water storage during fallow time.Therefore,in the fallow period,NT can effectively adapt to the climatic characteristics of the area and can effectively increase the soil water storage capacity.The water consumption of soil under NT and ST treatment was greater than that of CT treatment.Under the same cultivation,the water consumption of spring maize increased with the increase of density.Increasing nitrogen application could increase the maize water consumption of 0-200 cm.High nitrogen(H)treatment reduced the soil water storage of 0-200 cm soil layers for spring maize by 74.9 mm-111.1 mm during the jointing-tasseling stage.(2)Compared with CT,conservation tillage can increase the organic content of soil in the 0-60 cm soil layers.With the increase of nitrogen application,the content of soil organic matter increased,but the content of total phosphorus,available phosphorus and available potassium decreased,and the total nitrogen and nitrate nitrogen content significantly increased in the surface soil layer(0-20 cm).But the nitrogen fertilizer utilization efficiency varies,and abtain the highest value under low nitrogen treatment.The nitrogen utilization efficiency of the NT combined with low nitrogen and high density treatment reached 51.7%and 57.6%in 2018 and 2019,respectivly.(3)ST increasing nitrogen application and density can optimize plant height,stem diameter,SPAD content,and canopy structure of spring maize,increase photosynthetic rate at later stages of spring maize growth,and increase above ground dry matter accumulation.The dry matter accumulation of spring maize in the two years reached the highest under the treatment of ST combined with high nitrogen and high density.Increasing application of nitrogen fertilizer can also increase the nitrogen uptake of spring maize,and promote the transfer of plant nitrogen to grains.(4)Increasing the density significantly increased the ears number per square,and the application of nitrogen increased the kernel number of per ear and the weight of 100 grains,the interaction of three factors of tillage,nitrogen application and density had significant effects on water use efficiency of spring maize.Finally,a higher yield and a harvest index were obtained under the treatment of high density and high nitrogen.However,due to the relatively high initial investment in ST treatment,the final economic benefit is the highest under NT treatment.To sum up,in the semi-humid and drought-prone area of the Weibei dryland,the combined application of 150-225 kg/hm~2 nitrogen and 67,500 plants/hm~2 planting density in ST can not only improve the water use efficiency of spring maize,but also obtain relatively high maize yield benefits;NT combined application of 225 kg/hm~2 nitrogen and 67,500plants/hm~2 planting density can achieve higher economic benefits. |
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