氮肥减量分施促进甘薯根系分化与块根膨大

Lowering rate and split application of nitrogen fertilizer promote root differentiation and storage root enlargement of sweet potato

【目的】研究减氮运筹对甘薯根系生长发育、块根分化建成的影响,并讨论其与产量形成的关系,为高产高效甘薯栽培提供理论和技术依据。【方法】2016年和2017年在安徽省农业科学院本部试验基地黄棕壤上以商薯19和徐薯22为供试材料进行盆栽试验。以常规习惯基施氮100 kg/hm^2 (FP)为对照,在减氮20%的条件下,设置3种氮肥施用方式:全部基施(JS)、全部块根形成期(移栽后35 d)追施(KS)、50%基施+50%块根形成期追施(FS)。于移栽后35 d(块根分化建成后期)、80 d(块根膨大期)和收获期挖根取样,调查不定根数、不定根根长、粗根和单株有效薯块的根径范围、根尖数、根表面积、根体积等,测定根系活力、地上部和根系生物量。【结果】与FP处理相比,JS处理降低了单薯重,使块根产量显著降低,KS处理显著增加了单株有效薯块数,使块根产量分别提高7.61%(商薯19)和11.74%(徐薯22),FS处理提高了单株有效结薯数和单薯重,使块根产量分别增加22.10%(商薯19)和21.37%(徐薯22)。同时,FS处理较FP处理增加了块根形成期和块根膨大期根系总长度、根系表面积、根系体积和根尖数目,增强了根系活力,提高了地上部、根系及有效薯块干重和根系/地上部干重比值。相关分析表明,块根膨大期甘薯根系形态特征参数均与单薯重和产量呈显著或者极显著正相关。【结论】将施氮量由100 kg/hm^2减至80 kg/hm^2,并将其中一半氮肥在块根形成期追施,可有效促进甘薯根系生长和有效薯块的早期形成,保证单株结薯数,同时还可维持生育后期较高的根系活力,提高块根膨大期生物量和分配比例,有利于薯块的膨大和产量的增加。

【Objectives】Nitrogen supply levels play key roles in the formation of root tubers and their expansion in sweet potato production. The paper studied the effect of reducing conventional nitrogen application rate and topdressing half of the nitrogen on the root growth and development of sweet potato, in order to provide an efficient nitrogen management method in the cultivation of sweet potato.【Methods】Pot experiments were conducted in the Experimental Base of Anhui Academy of Agricultural Sciences in 2016 and 2017. The test soil was yellow brown soil and sweet potato cultivars used were Shangshu19 and Xushu22. The conventional N rate of100 kg/hm^2 in once basal application(FP) was used as control, the 20% less of N fertilizer rate with three application patterns were setup for treatments, including once basal application(JS), once topdressing at the 35 th day after transplanting(KS), and 50% basal and 50% topdressing at the 35 th day(FS). Root samples were collected at the stages of late tuber formation, tuber root expansion and maturing periods. The root morphological indexes, the root activity and biomass accumulation were measured.【Results】Compared with FP, KS treatment increased the tuberous root number per plant, and the storage root yield was increased by 7.61% for Shangshu19 and 11.74% for Xushu22;the FS treatment increased the tuberous root number per plant and fresh weight per tuberous root, enhanced the storage root yield by 22.10% for Shangshu19 and 21.37% for Xushu22. The sweet potato in FS treatment had longer root length, higher total root surface area, root volume, root tip number in all the tested growing periods. Their root activities, aboveground and root biomass, storage root biomass and the biomass ratio of root to aboveground were all higher than other treatments as a result. The tested indices for root growth and development at the 80 th day were significantly and positively related with the fresh weight per tuberous root and storage root yield.【Conclusions】Reducing nitrogen rate from 100 kg/hm^2 to 80 kg/hm^2 and topdressing half of the nitrogen at the root tuber formation stage could improve root growth and optimize root morphology, which is beneficial to the formation of effective root tubers and the maintaining of higher root physiological activities during later growth stage, eventually, increase the root biomass and average tuber weight, and thus producing a higher storage root yield.