钾肥用量对油菜产量及品质的影响

Effects of potassium application rate on the yield and quality of oilseed rape(Brassica napus L.)

【目的】我国南方大多数农田土壤有效钾含量偏低,缺钾胁迫已经成为一些地区油菜生产的主要限制因子。探明不同钾肥用量对油菜产量及籽粒品质的影响,为冬油菜生产中钾肥合理施用实现油菜高产、优质提供理论支撑。【方法】于2019—2021年在湖北省武穴市开展了连续2年田间试验,设置5个K_(2)O施用水平,分别为0(K_(0))、60(K_(60))、120(K_(120))、180(K_(180))和240(K_(240))kg/hm^(2)。从进入盛花期第15天起,每6天在K_(0)和K_(120)处理取样一次,测定角果不同部位氮钾含量。成熟期分析了油菜产量、产量构成、含油量、蛋白质含量、脂肪酸组成、硫甙含量、籽粒氮钾含量。【结果】1)钾肥施用显著提高了油菜产量,与K_(0)处理相比,施钾处理2019—2020和2020—2021年油菜产量分别提高了62.9%~103.7%和31.0%~59.2%,随着K_(2)O用量的增加油菜产量增加,当K_(2)O施用量达到120~180 kg/hm^(2)后,继续增施钾肥增产效果不显著。施钾增加了油菜单株角果数和每角粒数,进而提高油菜产量。2)钾肥施用改善了油菜籽的营养和饲用品质,与K_(0)相比,2019—2020年K_(180)处理、2020—2021年K_(120)处理油菜籽含油量分别显著提高了4.8%和6.9%;蛋白质含量则随着K_(2)O用量的增加呈现降低的趋势,2019—2020年的K_(180)和K_(240)处理、2020—2021年的K_(240)处理蛋白质含量的降幅达到显著水平,较K_(0)处理分别降低了9.1%和14.2%、12.1%;随着K_(2)O用量的增加,油菜籽油酸含量呈上升趋势,而硫甙含量呈下降趋势。施钾显著提高了油菜籽油分和蛋白质产量,随着K_(2)O用量的增加油分产量先显著增加,当K_(2)O施用量达到180 kg/hm^(2)后,继续增施钾肥油分产量不再显著增加,施钾处理间蛋白质产量没有显著差异。施钾显著降低了籽粒氮含量,与K_(0)处理相比,施钾处理2019—2020和2020—2021年籽粒氮含量分别降低了13.1%~21.9%和15.9%~22.0%;籽粒钾含量随着K_(2)O用量的增加而显著增加,与K_(0)相比,施钾处理2019—2020和2020—2021年籽粒钾含量分别增加了8.1%~37.8%和6.3%~27.1%。角果发育过程中,K_(0)处理籽粒氮含量始终高于K_(120)处理,而籽粒钾含量始终低于K_(120)处理。施钾还显著提高了角果的光合能力,与K_(0)处理相比,K_(120)处理角果的净光合速率(p_(n))提高了35.5%。【结论】钾肥施用能显著提高油菜单株角果数和每角粒数进而提高籽粒产量。施钾显著降低了籽粒的氮含量,提高了籽粒钾含量以及角果的光合能力,促进了籽粒油分的合成,提高了籽粒油分及蛋白质产量,同时改善了脂肪酸的组成,降低了硫甙含量。钾肥用量控制在K_(2)O 131~160 kg/hm^(2)范围内,能够在获得较高油分和蛋白质产量的同时,改善油菜籽的营养和饲用品质。

【Objectives】The available potassium(K)content in most farmland soils in south China is low,and K deficiency is a major limiting factor for oilseed rape production in some areas.Here,we investigate the effect of different K fertilizer application rates on oilseed rape yield and seed quality to provide theoretical support for the rational application of K fertilizer in winter oilseed rape production for high yield and quality.【Methods】A field trial was conducted for two consecutive years from 2019—2021 in Wuxue City,Hubei Province,with five K_(2)O application levels of 0(K_(0)),60(K_(60)),120(K_(120)),180(K_(180)),and 240 K_(2)O kg/hm^(2)(K_(240)).Since the 15 day at full flowering stage,silique samples were collected every six days in K_(0) and K_(120) plots for determination of N and K contents.At maturing stage,the yield,yield components,oil content,protein content,fatty acid composition,glucosinolate content,seed N and K contents were analyzed.【Results】1)Compared with K_(0),K application(P<0.05)increased rapeseed yield by 62.9%-103.7% and 31.0%-9.2% in 2020 and 2021,respectively.The rapeseed yield did not stop increasing until K_(2)O application rate beyond 120 kg/hm^(2).K application increased yield through enhancing the number of siliques per plant and the seed number per silique.2)K application improved rapeseed nutritional and feeding quality.Compared with K_(0),K_(180) increased rapeseed oil content in 2019-2020 and K_(120) in 2020-2021(P<0.05)by 4.8% and 6.9%,K_(180) and K_(240) in 2019-2020 and K_(240) in 2020-2021 decreased the protein content by 9.1%,14.2%,and 12.1%,respectively.With the increase in K_(2)O rate,the oleic acid in rapeseed showed an increasing trend,while the glucosinolate content decreased.K application(P<0.05)increased rapeseed oil and protein yield.There was no further increase in rapeseed oil yield at K_(2)O 180 kg/hm^(2) and above.There was no significant difference(P>0.05)in protein yield among the K application treatments.K application(P<0.05)reduced seed N content,with 13.1%-21.9% and 15.9%-22.0% reduction in 2019-2020 and 2020-2021,respectively,compared to K_(0).Seed K content(P<0.05)increased with increasing of K_(2)O rate,recording 8.1%-37.8%and 6.3%-27.1% in 2019-2020 and 2020-2021.During silique development,seed N content in K_(0) treatment was higher than in K_(120),while seed K content was lower than in K_(120).K fertilizer application also increased the photosynthetic capacity of silique,and the net photosynthetic rate(P_(n))of silique in K_(120) was 35.5% higher than K_(0).【Conclusions】K fertilizer application increases rapeseed oil yield through enhancing the silique number per plant and the seed number per silique.K application reduces rapeseed N but significantly increasing K content and photosynthetic capacity of silique,thereby promoting oil and protein synthesis,improving the composition of fatty acids,and reducing glucosinolate content.K_(2)O rate between 131-160 kg/hm^(2) improves rapeseed’s nutrition and feeding quality while recording higher oil and protein yields.