Effects of Nitrogen Application Rate and Plant Density on Lodging Resistance in Winter Wheat

Abstract

To make clear on the effects of nitrogen(N) application and plant density on lodging resistance and grain yield of win-ter wheat,we carried out a field experiment with split-plot design using a middle-spike cultivar,Shannong 15,in Tai'an,Shan-dong province,China in 2008-2009 and 2009-2010 growing seasons.The main plot was N application rate with levels of 180(N1) and 240 kg ha 1(N2),and the subplot was plant density with levels of 1.50(D1) and 2.25 million plants per hectare(D2).The lodging-resistance-related traits including morphological characters,chemical components in basal internode,culm lodging resis-tance index(CLRI),activities of enzymes involved in lignin synthesis,and grain yield were measured in different growth stages.The results showed that the grain yield was decreased with the increase of N rate or plant density,and the largest grain number per spike,1000-grain weight and grain yield were observed in the N1D1 treatment.The culm height of center of gravity and length of basal internode were larger in the N1 or D1 treatment than in the N2 or D2 treatment,whereas,the diameter,thickness,filling degree,and mechanical strength of the basal internode and the CLRI value showed an opposite trend.With the increase of N rate or plant density,the cellulose content,lignin content,C/N ratio of basal internode were decreased but the N content was increased.The interaction between N rate and plant density was significant,which resulted in poor lodging resistance under high N rate plus high plant density.Stepwize regression analysis indicated that N rate had more important effect on lodging resistance than plant density.Therefore,under the experimental condition in this study,the N1D1 treatment(180 kg ha 1 of pure N and 1.50 million plants per hectare) is a proper combination of N application and plant density,which may not only improve lodging resistance of winter wheat but also obtain high grain yield.