The Effect Of Brackish Water Supplementary Irrigation On The Distribution Of Soil Water And Salt And Watermelon Yield On The Gravel Mulching Field In The Arid Area In Central Ningxia

Drought climate and scare water resource are two main characteristics in the central of Ningxia. Using natural precipitation could not ensure to get a steady crop yield on the gravel-mulched field. To guarantee a steady and high yield, local people pumped brackish water from ground to irrigate crops. The aims of this paper are to investigate the effect of brackish water supplementary irrigation on water and soil salt distribution and growth, yield and quality of watermelon through a field fixed experiment; to make clear the effect of middle and long term brackish water irrigation on distribution characteristics of water and salt and yield and quality of watermelon. The main results were as follows:(1) Comparing before irrigation, soil water content in 0-20 cm layer obviously increased with the treatment of low amount water(W1),0-40 cm and 0-60 cm with middle and high amount water (W2 and W3) respectively. Brackish water supplementary irrigation with low amount water promoted watermelon water consumption of later growth stage, while reduced with middle and high irrigation amount water.(2) Comparing before irrigation, soil salinity in 40-60 cm has increased rapidly with low irrigation amount; Soil salinity in 0-60cm layer and in 0-80cm layer were leached with middle and high quantity, respectively. From the aspect of salinity change during watermelon growth stage, soil salt content in the upper layer increased with no-irrigation treatment, while deeper layer’s decreased. Soil salt content in 0-100cm layer had not changed. Soil salt content increased by 4.3% in 0-100cm layer with low quantity, however they reduced by 12.4% and 22.4% with the treatment of middle and high quantity, respectively.(3) Cl- and Na+content in the upper soil layer had a increasing tendency with low irrigation amount; Their content in the deeper soil layer decreased with increasing irrigation amount. Soil ions like SO42- and Ca2+ content in the deeper soil layer increased with increasing irrigation amount, while Mg2+ content decreased with increasing irrigation amount.(4) The watermelon fruit yields of no-irrigation treatment and low irrigation amount treatment (CK,W1) were higher than middle and high irrigation amount water treatment (W2,W3) in the experimental year. Soil salinity of watermelon expanding period to mature period had close relationship with watermelon yield. It could use polynomial characterized between them. The yield of watermelon could reach the maximum value when the soil salt content was 2.57ms/cm.(5) The number of brackish water irrigation year had a significant effect on soil water content, and that of 6th year and 10th year with brackish water irrigation has highest contents. Soil salinity during the vine stretching period tended to increase with increasing irrigated years, except for the treatment of irrigated 14 years. The yields of watermelon decreased with increasing growth years.