施氮对狼尾草在南方贫瘠旱坡地生长、能源品质及氮肥利用率的影响

为探究狼尾草作为生物质能源原材料在南方贫瘠旱坡地生长对氮素的响应,研究4个施氮水平(0、112.5、225.0和337.5 kg N·hm^-2)对能源型狼尾草桂能草1号农艺性状、产量、SPAD值、生物质能源品质及氮肥利用率的影响。结果表明,施用氮肥可促进狼尾草横、纵向生长,随施氮量的增加狼尾草的株高、茎粗和单位面积有效茎数逐步提高,但叶片叶绿素含量和鲜、干草产量的提高程度在施氮量超过225.0 kg N·hm^-2后,有饱和趋势。施用氮肥还可明显提高狼尾草纤维素含量、半纤维素含量、热值和折合标准煤产量,显著降低干物质、木质素和灰分含量,总体改善了狼尾草的能源利用品质;但施氮量达337.5 kg N·hm^-2时,狼尾草热值下降,且对折合标准煤产量的增加作用不明显,降低了狼尾草的能源利用品质。此外,在一定施氮量范围内(112.5~225.0 kg N·hm^-2),狼尾草氮肥利用效率并未随施氮量的增加而显著降低,但施氮量达337.5 kg N·hm^-2时,氮肥利用率显著降低。因此,狼尾草在南方贫瘠旱坡地种植,为获得理想的生物质能源材料需及时补充氮素营养,但施氮量不宜超过225.0 kg N·hm^-2。

Effect of nitrogen fertilizer on the growth,herbage bio-energy yield and nitrogen utilization of Pennisetum glaucum × P.purpureum on arid infertile hill land in South China

To explore the biomass production response of hybrid Pennisetum to nitrogen nutrition in arid hill land in South China,the effects of four different nitrogen (N) application levels (0,112.5,225.0 and 337.5 kg N · ha-1) on morpho-agronomic traits were studied.Parameters measured included yield,SPAD value,bio-energy characteristics and nitrogen utilization efficiency of P.glaucum × P.purpureum (cultivar Guinengcao-1).Application of N fertilizer promoted horizontal plant spread and shoot number,vertical growth,plant height,and stem diameter,but the fresh weight and hay yields were little changed at N fertilizer application rates above 225.0 kg N · ha-1.Application of nitrogen fertilizer also increased the contents of cellulose and hemicellulose,calorific value and the yield of standard coal,while significantly decreasing the contents of dry matter,lignin and ash.The calorific value decreased and the yield of standard coal showed little further increase when the rate of N fertilizer application was raised beyond 337.5 kg N · ha-1,with the result that bio-energy yield of Guinengcao-1 was also decreased.The nitrogen utilization efficiency of Guinengcao-1 did not decrease significantly with increase in N fertilization rate from 112.5 to 225.0 kg N · ha-1,but decreased significantly at 337.5 kg N · ha-1.Therefore,when growing Guinengcao-1 hybrid Pennisetum on arid infertile hill land in South China,N fertilizer is best applied at rates that optimize bio-energy yield.This is achieved when the N application rate is less than 225.0 kg N · ha-1.