Response To Plant Density And Nitrogen Application Rate For Maize Hybrids And Cultivation Approach For Higher-Yield With Higher-Efficiency In Northeast China

Maize is main grain crops in China, generating up to30%of the national grian production and playing an important role in stabilizing total grain production. Northeast China spring maize zone accounts for more than1/3of total maize area in China and40%of total maize production, which is of significance in national food security. To understand the characteristics of the evolution of Northeast spring maize varieties and the response to plant density and nitrogen application rate for maize hybrids from different eras can benefit new variety breeding and cultivation technique innovation for higher-yield with higher-efficiency of resource use in Northeast China. In this study,21typical spring maize varieties released over1970s to2000s in Heilongjiang, Jilin and Liaoning province were selected to investigate the evolution characteristics of productivity, plant morphology, nitrogen use efficiency and resistance to lodging and barren and response to plant density and nitrogen in2009and2010. A field experiment of tillage measure was conducted from2009to2011to study the effects of tillage measure on soil moisture, temperature, morphological characters and yield of maize.The main results are as follows:1. During the period1970s-2000s, plant height and ear height increased significantly by5.5cm10yr-1and4.5cm10yr-1, respectively.Leaf area per plant increased significantly by307cm10yr-1and the three ear leaves around ear increased by47cm210yr-1.The yield gains of per unit area and per plant were936kg hm-210yr-1and17.86g pl"-110yr-1.1000-kernel weight increased by19.55g10yr"1.There was a increasing trend of grain numbers per ear and no significant change tredn was found in shelling percentage and harvest index of varieties of different years. The resistance to lodging increased significantly and the barren plant rates decreased after1990s. Nitrogen use efficiency had a increasing trend, with PFP and NAE increasing by3.28kg kg-110yr-1and0.70kg kg-110yr-1, respectively, while NRE rosing by2.50percent10yr-1. The varieties in1990s had the highest value of NPE.2. There was no significant change trend in plant height with plant population density increaing while ear height rose significantly. With the population density increasing by10000plants per hectare, the ear height of varieties released in1970s,1980s,1990s and2000s increased by1.76,1.45,1.67and2.74cm, respectively, which lead to the upward displacement of plant center of gravity, and the leaf area per plant decreased by267,355,200and227cm2, while the three ear leaves aroud ear decreased by50,41,52and62cm2,respectively.3. For all varieties released in each era, grain yield per unit area showed a parabolic shape response with plant density increasing. The theoretical optimal density for the highest yield of varieties released in1970s,1980s,1990s and2000s was58190,49571,65210and64673plants ha’1. The theoretical optimal density rose by1750plant hm-210yr-1from1970s to2000s. With the population density increasing by10000plants per hectare, the grain yield per plant of varieties released in1970s,1980s,1990s and2000s decreased by11.29,12.71,13.71and17.30g, respectively while biomass per plant decreased by19.55,21.77,25.98and32.56g. Grain numbers per ear decreased by21,23,19and23kernels, while1000-grain weight decreased by7.33,7.13,7.64and8.23g and harvest index decreased by0.55,0.19,0.51and0.28percent, respectively.4. Nitrogen use efficiency showed a parabolic shape response with plant density increasing. The theoretical optimal density for the highest PFP of varieties released in1970s,1980s,1990s and2000s was57898,52114,63994and66294plants ha-1. The theoretical optimal density for the highest NAE of varieties was62216,61729,71357and62223plants ha-1.5. For all varieties released in each era, plant height, ear height, leaf area per plant and three ear leaves area around ear increased with the increasing of N fertilizer. With the N fertilizer increased100kg per hectare, the plant height of varieties released in1970s,1980s,1990s and2000s increased by5.45,5.53,4.63and6.77cm, while ear height increased by2.87,2.73,3.44and3.97cm, leaf area per plant increased by271,228,355and319cm2and three ear leaves area around ear increased by68,56,63and49cm2, respectively.6. For all varieties released in each era, grain yield per plant and grain yield per unit area showed a parabolic shape response to N application rate. The theoretical optimal nitrogen rate for highest yield of varieties released in1970s,1980s,1990s and2000s was283,365,332and331kg hm-2. With the N increased100kg per hectare, the grain numbers per ear increased by10,4,5and13kernels, while1000-grain weight increased by6.32,5.79,9.67and5.43g for the varieties released from1970s to2000s, respectively.7. For all varieties released in each era, N use efficiency decreased with higher N application rate. PFP and NRE of varieties of2000s were the highest and the second were ones of1990s. NAE and NPE were highest of1990s and the second were of2000s.8. There was different effect on characteristics of soil moisture, temperature and maize yield under different tillage management. The water conten and temperature in soil layer tillaged in autumn were higher than those of soil tillaged in spring. Compared to soil preparation in spring, soil preparation in autumn pomoted the yield increasing by8.63%and the1000-kernel weight increasing by7.26%. The topsoil daily mean temperature exists difference among different tillage management in different year types. Topsoil temperature of ridge rose or went down faster than flatten field, so flatten field could resist chilling better than ridge one. In drought stage, flatten topsoil was more beneficial to moisture conservation than that of ridge one. There was no difference in yield between fiatten-ridge management and ridge cultured. Flatten culturing could save diesel oil about22.2L hm-2compared to ridge.Productivity, N use efficiency and resistance to lodging and barren significantly improved for maize hybrids in Northeast China. Compared with Europe and the United States, density tolerance of maize varieties in Northeast China was obviously insufficient and there was great potential for improvement. With increasing amounts of nitrogen fertilizers, there was less output potential for varieties of2000s. Breeders should focus on increasing selection pressure in adversity and strengthen density-tolerant and N-efficient breeding of varieties.Maize high-yield cultivation ought to reduce amounts of N fertilizer or stable N fertilizer with increasing the density so as to coordinate high-yield and high efficiency of N.