| Drip irrigation is the partial irrigation, the limited wetting area can change the distribution of crops root system, and influence water-absorbing of root system, the growth of aerial parts ulteriorly and the final yield. Therefore, the relations between soil wetting area and crops root shape are important gist to determine the rate of soil moisture of drip irrigation, but there are quite few research results in view of this question in the domestic and foreign countries. In order to explore the effect of soil wetting area on the crops root growth, distribution, the water consumption, the growth characteristic of aerial parts ulteriorly and yield, so as to furnish theoretic gist for determining the rate of soil moisture under drip irrigation, this article took cotton as material, different soil wetting patterns were obtained by regulating the space of drip-lines and the drip discharge respectively. In the field experiment, two space of drip-lines (90cm and 130cm)were used for forming two soil wetting area, drying method was used for mensurating soil moisture. three drip discharges (1.393L/h,2.757 L/h,6.254 L/h) were used for forming three different soil wetting area, neutron probe and drying method were used for mensurating soil moisture, calculating the water consumption strength and capacity under different soil wetting patterns, cotton root distribution was obtained by using root aiguille way at cotton procreae stage, the growth characteristic of aerial parts ulteriorly was obtained at the five cotton growing stages, seeding stage, budding stage, flowering stage, belling stage and boll opening stage, the final yield was obtained at boll opening stage, the inner,outer and final cotton yield were calculated under different soil wetting patterns. The results are as follows:(1)The drip discharge had influence to soil moisture distribution. In horizontal, the large drip discharge resulted in a wider soil wetting pattern which its soil moisture uniformity was higher, the small drip discharge resulted in a narrower soil wetting pattern which its soil moisture uniformity was lower. In the soil depth, the large drip discharge, soil moisture concentrated in the surface layer of soil chiefly, the depth of soil wetting pattern was shallower, soil moisture uniformity was lower. the small drip discharge, the permeating velocity of soil moisture was larger, the soil moisture content was larger and the depth of soil wetting pattern was deeper near to the drip source of water, the drip irrigation water had no influence to soil moisture content almost apart from the drip source of water, the distribution of soil moisture in soil depth had smaller difference to the same locality.(2) Soil wetting pattern had influence to cotton-root distribution. the root length density decreased from the cotton-root axis to both sides in horizontal, the root distribution uniformity of wider-shallower soil wetting pattern was higher, the inner and outer cotton-root distribution had smaller difference, but the root distribution uniformity of narrower-deeper soil wetting pattern was lower, the inner and outer cotton-root distribution had larger difference, the average root length density difference is 236.80 m/m3.(3) The growing performances of the root length were polynomial distribution under different soil wetting pattern, the peaks of root length all appeared 80 days after cotton germinated, then decreased with growing performance. The growing performances of the root weight were Gaussian distribution under different soil wetting pattern, the peaks of root weight all appeared 110 days after cotton germinated, then decreased with growing performance, but the root weight of wider-shallower soil wetting pattern was nearly twice as large as the root weight of narrower-deeper soil wetting pattern.(4) Consumption rate of soil water had smaller difference before cutting the cotton apex under different soil wetting pattern, then started to appear difference. Consumption rate of soil water was 6.03mm/d larger under wider-shallower soil wetting pattern, but 5.55mm/d under narrower-deeper soil wetting pattern. The total water consumption was also larger under wider-shallower soil wetting pattern, and lower under narrower-deeper soil wetting pattern, the total water consumption were 546mm,498mm Respectively.(5) The growing performances of the cotton plant and leaves under different soil wetting pattern were similar, and the cotton plant, leaves of the inner cotton was larger than the outer cotton. The growing performances of plant was Logistic distribution, The growing performances of leaves was Gaussian distribution, the peaks of leaves appeared 90 days after cotton germinated, the plant was smaller and the single cotton leaves was larger, but the cotton plant and leaves had smaller difference between the inner cotton and the outer cotton under wider-shallower soil wetting pattern, the average difference was 4cm, 94.87cm2; The cotton plant and leaves of the inner cotton were all larger than the outer cotton, and the cotton plant and leaves had larger difference between the inner cotton and the outer cotton under wider-shallower soil wetting pattern, the average difference was 5.1cm,234.72cm2.(6) Soil wetting pattern had influence to cotton yield. Cotton yield was higher under wider-shallower soil wetting pattern, and lower narrower-deeper soil wetting pattern, their practical yield were 4663.7kg/hm2,3990.1kg/hm2; The inner cotton yield had smaller difference under different soil wetting pattern, the difference was only 31.7 kg/hm, but the outer cotton yield was higher under wider-shallower soil wetting pattern, and lower narrower-deeper soil wetting pattern, the difference may be up to 641.6kg/hm2. So that improving the uniformity of soil wetting pattern was helpful for the uniformity of plant growth and higher yield finally.(7) The cotton-root distribution uniformity was lower, the difference of shoot growth characteristics and yield between the inner row and the outer row were larger under narrower-deeper soil wetting pattern; The cotton-root distribution uniformity was higher, the difference of shoot growth characteristics and yield between the inner row and the outer row were smaller under wider-shallower soil wetting pattern, the plant was small but uniform, the time that the bolls developed was early because the cotton-root distribution was shallower, the cotton harvest time was in advance,the yield was still higher. So the wider-shallower soil wetting pattern was good for controlling the plant growth, in the late growth stage of cotton, if the weather was bad, the precocity for cotton would increased cotton yield under wider-shallower soil wetting pattern. |
