施氮水平对甜高粱主要农艺性状及其与干物质产量相关关系的影响

为探求甜高粱干物质产量与主要农艺性状的关系以及不同施氮水平对两者相互关系的影响,本研究以大力士甜高粱为材料,采用完全随机区组设计进行两年田间试验,测定不同施氮水平(0,100,200,300,400,500kgN/hm~2)下甜高粱的株高、茎粗、绿叶数、茎叶比、鲜干比、叶面积指数和干物质产量7个参数,并对上述参数进行了相关性分析、多元回归分析和通径分析。试验结果表明,株高,叶面积指数和茎粗均与干物质产量呈极显著正相关关系(P0.01),相关系数分别为r=0.921**,r=0.865**,r=0.758**。通径分析表明,株高是决定干物质产量的主要农艺性状,茎叶比和叶面积指数与干物质产量的关系对不同施氮水平有不同响应。较低施氮水平(0,100kgN/hm~2)下,茎叶比对干物质产量的直接作用最大(P=0.925),叶面积指数对干物质产量的直接作用最小(P=0.162)。中等施氮水平(200,300kgN/hm~2)下,茎叶比对干物质产量的影响降低(P=0.073),叶面积指数对干物质产量的直接作用增加(P=0.797)。较高施氮水平(400,500kgN/hm~2)下,茎叶比和叶面积指数对干物质产量的直接作用均为负值(P=-0.125,P=-0.040)。施氮量为200~400kgN/hm~2时,干物质产量较高。综上可知,在较高施氮条件下,合理密植是获得较高干物质产量的关键。当供氮水平较低时,应注意收获时间的选择,以便更好地兼顾干物质产量和饲草营养价值。

Effects of nitrogen on agronomic traits and dry matter yield and their relationship in sweet sorghum

This study was conducted to determine the relationship between dry matter (DM)yield and agronom-ic traits of sweet sorghum (Sorghum bicolor cv.‘Hunnigreen’)using correlation and path coefficient analysis under different rates of nitrogen (0,100,200,300,400,500 kg N/ha).The experiment was set up in eastern China during 2009-2010 and 7 agronomic traits of sorghum were evaluated.Results showed that DM yield was positively correlated (P <0.01)with plant height (r=0.921 ** ),leaf area index (LAI,r=0.865 ** )and stem diameter (SD,r=0.758 ** ).Plant height and LAI produced the strongest path coefficient (P =0.638,P =0.391)for DM yield.Plant height was the best indicator of DM yield using stepwise regression analysis.The contribution of stem∶leaf ratio (S∶L ratio)and LAI to DM yield differed under different rates of N fertilizer.S∶L ratio and LAI had positive path coefficient (P =0.925,P =0.162)for DM yield under lower N fertilizer rate (0,100 kg N/ha).LAI had a positive path coefficient (P =0.797)for DM yield under intermediate N fer-tilizer rates (200,300 kg N/ha),but had a negative path coefficient for DM yield under higher N fertilizer rates (400,500 kg N/ha).The Effect of S∶L ratio on DM yield decreased with increasing N rate.DM yield was highest at N rates of 200-400 kg N/ha.Plant population was important for higher DM yield at higher rates of N fertilizer.Under lower N fertilizer rates,harvest date was a key issue in terms of the trade-off between DM yield and nutritive value of sweet sorghum.