| Effects of dense planting with less nitrogen fertilizer on root system development and water use efficiency of direct-sowed rapeseed in hilly dryland area in southwest of China |
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| DOI：10.7606/j.issn.1000-7601.2021.01.02 |
| Key Words: nitrogen rate planting density population regulation root system development water use efficiency (WUE) rapeseed (Brassica nupus L.) |
| Author Name | Affiliation | | SHI Chao | College of Agronomy and Biotechnology, Southwest University/Engineering Research Center of South Upland Agriculture, Ministry of Education/Key Laboratory of Eco\|environments in Three Gorges Reservoir Region, Ministry of Education, Chongqing 400715, China | | XING Yi | College of Agronomy and Biotechnology, Southwest University/Engineering Research Center of South Upland Agriculture, Ministry of Education/Key Laboratory of Eco\|environments in Three Gorges Reservoir Region, Ministry of Education, Chongqing 400715, China | | FENG Jun | College of Agronomy and Biotechnology, Southwest University/Engineering Research Center of South Upland Agriculture, Ministry of Education/Key Laboratory of Eco\|environments in Three Gorges Reservoir Region, Ministry of Education, Chongqing 400715, China | | ZHOU Quan | College of Agronomy and Biotechnology, Southwest University/Engineering Research Center of South Upland Agriculture, Ministry of Education/Key Laboratory of Eco\|environments in Three Gorges Reservoir Region, Ministry of Education, Chongqing 400715, China | | WANG Longchang | College of Agronomy and Biotechnology, Southwest University/Engineering Research Center of South Upland Agriculture, Ministry of Education/Key Laboratory of Eco\|environments in Three Gorges Reservoir Region, Ministry of Education, Chongqing 400715, China | | Wu Haiyan | Yunyang Committee of Agriculture, Chongqing 404500, China | | Ran Tailin | Yunyang Committee of Agriculture, Chongqing 404500, China | | Xiang Xinhua | Yunyang Committee of Agriculture, Chongqing 404500, China |
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| Abstract: |
| In the hilly area of southwestern China where the eco\|environment is fragile and soil erosion is serious, the combination of optimal fertilization and population regulation is of great significance for coping with seasonal drought, achieving high and stable yield, and saving fertilizer in rapeseed production. A two\|factor split plot experiment was designed, in which nitrogen fertilizer (pure N) was the main treatment and planting density was the sub\|treatment. There were three levels of N fertilizer including N1 (108 kg·hm-2), N2 (144 kg·hm-2), and N3 (180 kg·hm-2), and four levels of planting density including D1 (150 000 plants·hm-2), D2 (225 000 plants·hm-2), D3 (300 000 plants·hm-2), D4 (375 000 plants·hm-2). There were 12 treatments in total, in which N3D1 (traditional planting mode) was used as control. The root\|shoot ratio, root morphology (root length, root surface area and root volume) and soil storage capacity at different growth stages, as well as economic yield, water use efficiency (WUE) and economic benefit of rapeseed under different N fertilizer and planting density were analyzed. The results showed that the amount of N application significantly affected the root\|shoot ratio, total root length and total surface area of the bud stage, pod stage and maturity stage, and significantly affected the total root length and total volume of the bud stage. The planting density significantly affected the root\|shoot ratio at the bud stage and the total root volume during the pod\|setting stage and significantly affected the total root surface area and total root volume of the bud stage. During the period of pod stage, the biomass accumulation rate of the above mentioned part was at the maximum, and the root\|cap ratio of this period was 55.5% lower than that of the bud stage. In addition, root\|crown ratio at seedling stage was negatively correlated with economic yield (r=-0.673*). The reduction of N fertilizer effectively increased the soil water storage and total water consumption during the growth period, and it was more significant after 40% reduction of N fertilizer. The former is N1>N2>N3, while the latter is N3>N2>N1. Compared with N3, the average total water consumption of each treatment under N1 and N2 decreased by 5.03% and 3.24%. Under N2, the economic yield and water use efficiency increased significantly with the increase of planting density; both economic returns and water economic returns showed similar and significant growth trends; Among them, N2D3 and N2D4 increased the economic returns per hectare by 290.73 yuan and 503.37 yuan, and the economic returns on water increased by 2.72% and 9.93%. So, the N application rate of 144 kg·hm-2 and the planting density of 300 000 plants·hm-2 or 375 000 plants·hm-2 is an optimal planting mode for saving fertilizer and increasing efficiency in the production of direct sowed rapeseed in dryland in the hilly area of southwestern China. |
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