低氮密植栽培对超级稻产量和氮素利用率的影响

Effect of Low Nitrogen Rate Combined with High Plant Density on Grain Yield and Nitrogen Use Efficiency in Super Rice

为了研究低氮密植栽培对水稻分蘖发生及成穗率、干物质积累及其转化、氮素利用率和产量的影响,2012—2013年以超级稻Y两优1号为材料,在湖南长沙和海南澄迈进行了施氮量（75、150、225kgNhm–2）与栽插密度（68、40、27、19穴m–2）,每穴苗数（单、双、三本穴–1）与栽插密度（40、27、19、14穴m–2）的大田栽培试验。结果表明,在基本苗数相同或相近的条件下,减苗增密在齐穗期和成熟期的干物质量及产量分别比增苗减密高10.5%、5.2%和2.9%,有效穗数对产量的贡献最大,达到显著水平；在低氮密植条件下,有效分蘖期缩短6d左右,分蘖成穗率、表观转化率、氮肥偏生产力和氮素籽粒生产效率分别提高10.9%、21.0%、150.6%和19.6%。在施氮量为75kgNhm–2的密植（40-68穴m–2）条件下,齐穗期和成熟期的干物质量及长沙点产量分别比中、高氮（150-225kgNhm–2）常规密度（19-27穴m–2）低3.2%、7.5%和1.2%,但差异不显著,而澄迈点产量在2012年和2013年分别比之低5.2%和高9.1%,且差异均达显著水平。在施氮量为150kgNhm–2的密植条件下,成熟期干物质量比高氮常规密度低1.7%,但齐穗期干物质量和产量比高氮常规密度高10.3%和3.3%。因此,超级稻采用低氮密植栽培,在100-150kgNhm–2和40穴m–2条件下提早了够苗期,增加了有效穗数,提高了分蘖成穗率和结实率,加之齐穗期适宜的干物质积累和较高的表观转化率,有利于高产的形成和氮肥利用率的提高。

In order to study the impacts of low nitrogen rate combined with high plant density on tillering, earbearing tiller per-centage, dry matter accumulation, apparent transformation rate, N-use efficiency and grain yield, field experiments with three nitrogen rates （75, 150, and 225 kg N ha–1） and four plant densities （68, 40, 27, and 19 hill m–2） as well as with three levels of number of seedlings per hill （1, 2, and 3 seedling（s） hill–1） and four plant densities （40, 27, 19, and 14 hill m–2） were conducted using super rice cultivar Y-liangyou 1 at Changsha, Hunan Province and Chengmai, Hainan Province in 2012–2013. The results showed that when seedlings per unit area were the same orapproximate in combination with reducing seedlings per hill and in-creasing density （RSID）, the dry matter accumulated 10.5% and 5.2% more than those with increasing seedlings per hill and re-ducing density （ISRD） at heading and maturity, respectively. RSID also produced 2.9% higher grain yield than ISRD. Panicles m–2 had the highest and significant contribution to grain yield in RSID. Productive tillering stage was shorter by six days, and earbearing tiller percentage, apparent transformation rate （ATR）, partial factor productivity of applied nitrogen （PEP） and internal utilization efficiency of nitrogen （IE） were respectively higher by 10.9%, 21.0%, 150.6%, and 19.6% under low nitrogen rate （75–150 kg N ha–1） combined with high plant density （40–68 hills m–2） than under higher nitrogen rate （225 kg N ha–1） combined with low plant density （19–27 hills m–2）. The combination of applying 75 kg N ha–1 and transplanting 40–68 hills m–2 produced 3.2% and 7.5% biomass less than those of applying 150–225 kg N ha–1 and transplanting 19–27 hills m–2 at heading and maturity, respectively, but the differences were not significant. Meanwhile, the former combination decreased 1.2% and 5.2% grain yield at Changsha in two years and at Chengmai in 2012, respectively, while increased 9.1% at Chengmai in 2013, and the differences were significant at Chengmai. However, the combination of applying 150 kg N ha–1 and transplanting 40–68 hills m–2 produced 10.3% biomass and 3.3% grain yield more than that of applying 225 kg N ha–1 and transplanting 19–27 hills m–2, except for biomass decreased 1.7% at maturity. Therefore, the adoption of low nitrogen rate （100–150 kg N ha–1） combined with high planting density （40 hills m–2） would improve both grain yield and N-use efficiency for super rice due to reaching the projected tillers earlier, increasing panicles, improving earbearing tiller percentage and seed setting rate, and having suitable biomass and higher ATR at heading stage.