Research Of Efficient Fertigation Mode Of Mechanically Harvested Cotton With Drip Irrigation Under Plastic Film

Fertigation technology of drip irrigation under plastic film has many advantages like water and fertilizer saving, production increasement, high efficiency, and so on. It is therefore the most suitable crop planting in arid and semi-arid regions of Northwest China. The study of fertigation on cotton with drip irrigation under plastic film was mainly focused in the Xinjiang area, but the fertigation research of 1 film with 3 laterals and 6 crop rows mechanically harvested cotton in the new cotton planting area of western Inner Mongolia was comparely few. In this article, the effect of irrigation amount, drip tape on soil moisture uniformity and different water and nitrogen treatment(Irrigation levels: W1-216 mm, W2-288 mm, W3-360 mm, W4-432 mm; Nitrogen levels: N0-60 kg/hm2, N1-127.5 kg/hm2, N2-195 kg/hm2, N3-262.5 kg/hm2) on cotton growth, dry matter accumulation, nutrient absorption, root distribution, water consumption, yield and fiber quality were studied in a field experiment in Alxa Left Banner of Alxa League in Inner Mongolia.The main results were as follows:(1) Presenting the optimum technical parameters of drip irrigation for mechanically harvested cotton planting mode in Western Inner Mongolia. For the two typical soils in Western Inner Mongolia, under mechanically harvested cotton drip irrigation tape laying mode, the combination of 37.5 mm irrigation requirement, 30 cm dripper spacing, 2 L/h dripper discharge for the condition of silty clay, dripper discharge 3 L/h for the condition of sandy loam is appropriate irrigation technical parameters.(2) Clarifying the regulation effects of different water and nitrogen treatments on the above- and below-ground growth and development of cotton. With W1 and W2 irrigation amount, the N1 nitrogen treatment favor to maintain a good plant type, increase shoot biomass and improve boll number per plant, but excessive application of nitrogen restrain the formation of shoot biomass. The increasing of irrigation was conducive to the effect of nitrogen fertilizer production. The W3 and W4 treatments help to increase plant height, leaf area index, plant boll number and shoot biomass, but excessive nitrogen suppressed shoot biomass formation, thus improve boll flower abscission rate. Drought stress could induce the distribution of photosynthetic products in roots and increase root dry weight and root length. In 0 to 10 cm soil layer, the root mass density of W2 treatment was highest, but for the other layers, root mass density gradually decreased with the increase of irrigation water amount. W1 treatment promoted root growth in each soil layers, and the proportion of root in deeper layers increased.(3) The effects of different water and nitrogen treatments on water consumption and nitrogen uptake of cotton were revealed. The total consumption of water for cotton growth period was 392.6 to 551.0 mm, and it is mainly concentrated in the flowering stage, followed by the bud stage, seedling stage and boll opening stage. Under the same nitrogen application level, the water comsumptation of cotton was in proportion to the irrigation amount, but it didn’t change obviously with the increase of nitrogen application rate. In the boll opening stage, the nitrogen uptake order of different cotton organs was seed cotton > stems and leaves > boll hull > root. The nitrogen uptake of seed cotton accounted for over 59% of the whole cotton plant nitrogen uptake, and maily accumulated in reproductive organs. Water stress inhibited the absorption of nitrogen fertilizer, and the amount of nitrogen of W1 treatment was lower as a whole. Increasing irrigation and nitrogen amount showed different degrees of promoting effects on the vegetative and reproductive organs of cotton, and the nitrogen required for cotton reproductive organs to reach the highest nitrogen absorbing amount was lower than vegetative organs.(4) Based on the coupling effect of water and nitrogen in cotton, the suitable irrigation and fertilization combination for cotton planting in the west of Inner Mongolia province was put forward. At no more than the level of water requirement of cotton, with the increase of irrigation amount, seed cotton yield increased gradually, while seed cotton yield increased first and then decreased with the increase of nitrogen fertilizer. Under different irrigation amount, nitrogen fertilizer could increase yield only in less 195 kg/hm2(N2). When the nitrogen fertilizer amount was greater than that, it will lead to yield reduction. The W3N2 treatment had the highest seed cotton yield of 7100.8 kg/hm2 in 2014, and the water use efficiency was 1.30 kg/m3. In 2015, the W4N2 treatment achieved the highest seed cotton yield, and the W3N2 decreased by 10.2% compared with W4N2. Both water use efficiency were 1.24 kg/m3 and 1.22 kg/m3 respectively. In order to obtain the highest seed yield, W4N2 treatment was the most suitable combination of water and nitrogen for mechanical harvested cotton planting in Western Inner Mongolia. When considering the ecological environment sustainable development and local frost free period is short, and avoiding growth period postpone, W3N2 treatment seemingly is the best combination.