Salt Accumulation In Root Zone Research Articles

Effects of irrigation and fertilizer levels on the distribution of water and salt in saline field and maize yield

Agriculture development in arid and semi-arid saline areas is seriously affected by water resources scarcity and excessive fertilization. Understanding the effects of different irrigation and fertilization levels on soil water and salt distribution and silage maize yield would provide scientific basis for determining appropriate irrigation and fertilization amount. The experiment was carried out in a saline field of the Datong Basin in 2015 and 2016. There were three irrigation levels, with the upper limit of soil moisture being controlled at 100% (W1), 90% (W2) and 80% (W3) of the field water capacity. Irrigation amount was calculated based on the average actual water content before irrigation of each treatment. There were four fertilization levels in 2015, 900 kg·hm-2 (F1), 750 kg·hm-2 (F2), 600 kg·hm-2(F3), and 450 kg·hm-2(F4), and three levels in 2016 (F1, F2, and F3). The total nutrient content of the slow-release compound fertilizer was 48%, with a 30:12:6 ratio of N:P2O5:K2O. Results showed that the surface conductivity of soil increased with the increases of fertilizer application levels. The effects of fertilization on soil salinity in 0-10 cm was significant. Compared with F1, the average EC of F2 in 0-10 cm was decreased by 25.6%-42.7% in 2015 and by 6.4%-7.7% in 2016, respectively. The water content in 20-80 cm decreased with the increases of fertilizer application levels. Compared with F1, the average soil water content in 20-80 cm soil layer of F2, F3, and F4 increased by 5.9%, 16.7% and 16.7% in 2015, and that of F2 and F3 increased by 13.3% and 16.7% in 2016, respectively. The yield of F1 and F2 was higher than that of F3 and F4, and W3 was lower than W1 and W2 in both years. There was no significant difference in yield between F1 and F2. Compared with W1, decrease in yield of W2 was less than 15%. Therefore, the application of compound fertilizer 600-750 kg·hm-2(nitrogen content 180-270 kg·hm-2), and irrigation levels W1 and W2 were suggested to ensure high yield of forage maize in saline soil in this area, without salt accumulation in root zone.

Untangling the effects of shallow groundwater and deficit irrigation on irrigation water productivity in arid region: New conceptual model

Water scarcity and salt stress are two main limitations for agricultural production. Groundwater evapotranspiration (ETg) with upward salt movement plays an important role in crop water use and water productivity in arid regions, and it can compensate the impact of deficit irrigation on crop production. Thus, comprehensive impacts of shallow groundwater and deficit irrigation on crop water use results in an improvement of irrigation water productivity (IWP). However, it is difficult to quantify the effects of groundwater and deficit irrigation on IWP. In this study, we built an IWP evaluation model coupled with a water and salt balance model and a crop yield estimation model. As a valuable tool of IWP simulation, the calibrated model was used to investigate the coupling response of sunflower IWP to irrigation water depths (IWDs), groundwater table depth (GTDs) and groundwater salinities (GSs). A total of 210 scenarios were run in which five irrigation water depths (IWDs) and seven groundwater table depths (GTDs) and six groundwater salinities (GSs) were used. Results indicate that increasing GS clearly increases the negative effect on a crop's actual evapotranspiration (ETa) as salt accumulation in root zone. When GS is low (0.5–1g/L), increasing GTD produces more positive effect than negative effect. In regard to relatively high GS (2–5g/L), the negative effect of shallow-saline groundwater reaches a maximum at 2m GTD. Additionally, the salt concentration in the root zone maximizes its value at 2.0m GTD. In most cases, increasing GTD and GS reduces the benefits of irrigation water and IWP. The IWP increases with decreasing irrigation water. Overall, in arid regions, capillary rise of shallow groundwater can compensate for the lack of irrigation water and improve IWP. By improving irrigation schedules and taking advantages of shallow saline groundwater, we can obtain higher IWP.

RESPONSE OF TOMATO TO IRRIGATION WITH SALINE WATER APPLIED BY DIFFERENT IRRIGATION METHODS AND WATER MANAGEMENT STRATEGIES

In a field experiment the effects of irrigation with saline drainage water (seasonal average of 4.5 dS/m) and non-saline water (0.55 dS/m) applied by two different water management strategies (cyclic or blended saline water with non-saline water in different ratios) and two different irrigation methods (drip or furrow) were studied on growth and productivity of tomato (Lycopersicon esculentum Mill cv Floradade), salinity distribution in root zone and water use efficiency. The results indicated that salinity (at 3 dS/m and above) significantly reduced leaf area, height and dry weight of plant as well as fruit weight and number and hence total yield, but increased fruit T.S.S. content. Water use efficiency (WUE) was increased by using water with low and moderate salinity levels (2 and 3 dS/m) as compared to those obtained with non-saline water (0.55 dS/m) or the highest salinity level (4.5 dS/m). Salinity increased Na, Cl and Mg contents as well as dry matter percentage, but decreased N, P, K and Ca contents in leaves of plants. Drip irrigation enhanced tomato growth, yield and WUE under both saline and non-saline conditions, but showed more advantages under saline conditions as compared with furrow irrigation. Drip irrigation method did not allow salt accumulation in root zone (wetted area beneath the emitters and the plants). However, more salt accumulated in root zone (30 cm apart from irrigation source) of furrow irrigated plants. Mixing saline with non saline waters (blending) produced better results in terms of more vigorous vegetative growth and highest yield, than that produced by alternate saline with non saline water (cyclic). Using saline water up to 3 dS/m produced yield that was not significantly differ than that produced by non saline water if applied by drip irrigation and blended water management.

Effects of Irrigation Water Quality and Drip Tape Arrangement on Soil Salinity, Soil Moisture Distribution, and Cotton Yield (Gossypium hirsutum L.) Under Mulched Drip Irrigation in Xinjiang, China

More and more attention is being focused on saline water utilization in irrigation due to the shortage of fresh water to agriculture in many regions. For purpose of reducing the risks of using of saline water for irrigation, the mechanism of soil moisture and salinity distribution and transport should be well understood for developing optimum management strategies. In this paper, field experiments were carried out at Junggar Basin, China, to study the effects of drip irrigation water quality and drip tape arrangement on distribution of soil salinity and soil moisture. Six treatments were designed, including two drip tape arrangement modes and three irrigation water concentration levels (0.24, 4.68, and 7.42 dS m−1). Results showed that, soil moisture content (SMC) directly beneath the drip tape in all treatments kept a relatively high value about 18% before boll opening stage; the SMC in the narrow strip in single tape arrangement (Ms) plot was obviously lower than that in the double tapes arrangement (Md) plot, indicating that less sufficient water was supplied under the same condition of irrigation depth, but there was no significant reduction in yield. Mulching had not significant influence on salt accumulation but the drip tape arrangement, under the same condition of irrigation water depth and quality, compared with Md, Ms reduced salt accumulation in root zone and brought about relatively high cotton yield.

Effect of improved cultural practices on crop yield and soil salinity under relatively saline groundwater applications

The salinity in the root zone increases with the application of relatively saline groundwater. Therefore, a limited water supply coupled with high pumping cost and salinity hazards, makes it more important than ever that irrigation water be used efficiently and judiciously. In the present study, farmer's practices of irrigation application methods (Field 1) were compared with the water saving techniques (Field 2) for crop yield and salinization for two years with maize–wheat–dhanicha cropping pattern. For maize crop, regular furrow method of irrigation was used in Field 1 and alternate furrow method of irrigation was used in Field 2. For wheat experiments, basin irrigation method of water application was compared with bed and furrow method. For dhanicha, basin irrigation was applied in both the fields. The results showed that about 36% water was saved by applying irrigation water in alternate furrows in each season without compromising the maize crop yield. The salt accumulation in root zone in alternate furrow field was less than that in regular furrow field. The salinity level near the surface increased substantially in both the fields. The water saving in wheat crop under bed and furrow was 9–12% in both seasons. The salinization process in both fields during wheat crop was almost same except redistribution of salts throughout the root zone in basin field of wheat. The salinity developed in root zone during two major growing seasons was leached in monsoon.