Shuqin Wan

Soil Salinity Changes Under Cropping with Lycium barbarum L.and Irrigation with Saline-Sodic Water

In order to utilize the wasted saline-sodic soils under shallow groundwater condition, a 3-year field study was carried in a field cropped with Lycium barbarum L. and irrigated by drip irrigation with saline groundwater under the water table depth of 30-40 cm in the northern Yinchuan Plain, China. Effects of cropping duration (one, two, and three years) on soil salinity, soil solution composition, and pH in three adjacent plots were investigated in 2008. Results showed that a high irrigation frequency maintained high soil water potential and subsequently facilitated infiltration and downward movement of water and salt in the crop root zone. Salt accumulated on the edges of the ridges, and soil saturated-paste electrical conductivity (ECe) was higher in the edge. Concentrations of Na(+), Ca(2+), Mg(2+), Cl(-), and SO(4)(2-) in the soil increased with the soil depth as did the ECe, while FICO(3)(-) and pH had a relative uniform distribution in soil profile. As planting year increased, the ECe and soil salts in the field had a decreasing tendency, while in the root zone they decreased immediately after irrigation and then remained relatively stable in the following growing seasons. HCO(3)(-) and pH had little change with the planting year. Results suggested that the application of drip irrigation with saline water could ameliorate saline-sodic soil and provide a relatively feasible soil environment for the growth of salt-tolerant plant Lycium barbarum L. under the saline-sodic soils with shallow groundwater.

Use of a New Controlled-Loss-Fertilizer to Reduce Nitrogen Losses during Winter Wheat Cultivation in the Danjiangkou Reservoir Area of China

ABSTRACT The use of a new controlled-loss-fertilizer (CLF) to reduce nitrogen loss from the Danjiangkou Reservoir of China was explored. Specifically, a three-year experiment was conducted to identify the optimum fertilizer rate for CLF used in wheat production. The treatments included four CLF levels, 20% (20% F), 35% (35% F), 50% (50% F), and 100% (100% F), of the local recommended fertilization dose (LRFD), and traditional fertilizers with the same dose as 50% F as the control (CF). Treatment 50% F with an equivalent fertilizer rate decreased nitrogen (N) runoff loss and leaching loss by 21.6% and 24.5%, while leading to a 9.8% increase in soil residual mineral N when compared to CF. Treatments 50% F and 100% F produced higher wheat yield than the other treatments. At the same fertilizer rate, the grain yield of the 50% F treatment was 5.5% higher than that of CF. Regression analysis of the yield relative to the CLF rate revealed that the optimum CLF rate was about 77% of the LRFD. Overall, the results indicate that CLF with 77% of the LRFD could be the optimum rate for minimizing nitrogen loss and increasing yield and should be considered for wheat production in the area.

Comparison of Two Dripper Line Designs to Assess Cotton Yield, Water Use, and Net Return in Northwest China

This study aimed to compare the effects of two types of drip irrigation line design on cotton yield, water use, and net returns. The experiments were carried out in the arid region of Xinjiang, Northwest China, during 2009-2010 growing years. The two types of lateral placement are commonly used by the local farmers in the area: double lines (two laterals controlling four rows) and single line designs (one lateral controlling four rows). The results indicated that less irrigation water was applied by single line compared with double lines design. This implies that more irrigation water could be saved using single line, by reducing the water consumption of cotton. The emergence rates for double lines were 2 and 6% higher than those for single line design in 2009 and 2010. The seed cotton yields for double lines design were 5.76 and 6.41 Mg ha(-1) which were 13 and 9% higher than for single line design in 2009 and 2010, respectively. Single lines could however lower the investment cost compared to double lines, which produced 10 and 7% more net income in 2009 and 2010, respectively. By contrast, the double lines was more profitable and suitable for the farmers in Northwest China than single line design.

Effects of water application intensity of microsprinkler irrigation on water and salt environment and crop growth in coastal saline soils

Laboratory and field experiments were conducted to investigate the effects of water application intensity (WAI) on soil salinity management and the growth of Festuca arundinacea (festuca) under three stages of water and salt management strategies using microsprinkler irrigation in Hebei Province, North China. The soil water content (e) and salinity of homogeneous coastal saline soils were evaluated under different water application intensities in the laboratory experiment. The results indicated that the WAI of microsprinkler irrigation influenced the e, electrical conductivity (ECe) and pH of saline soils. As the WAI increased, the average values of e and ECe in the 0-40 cm profile also increased, while their average values in the 40-60 cm profile decreased. The pH value also slightly decreased as depth increased, but no significant differences were observed between the different treatments. The time periods of the water redistribution treatments had no obvious effects. Based on the results for e, ECe and pH, a smaller WAI was more desirable. The field experiment was conducted after being considered the results of the technical parameter experiment and evaporation, wind and leaching duration. The field experiment included three stages of water and salt regulation, based on three soil matric potentials (SMP), in which the SMP at a 20-cm depth below the surface was used to trigger irrigation. The results showed that the microsprinkler irrigation created an appropriate environment for festuca growth through the three stages of water and salt regulation. The low-salinity conditions that occurred at 0-10 cm depth during the first stage (-5 kPa) continued to expand through the next two stages. The average pH value was less than 8.5. The tiller number of festuca increased as SMP decreased from the first stage to the third stage. After the three stages of water and salt regulation, the highly saline soil gradually changed to a low-saline soil. Overall, based on the salt desalinization, the microsprinkler irrigation and three stages of water and salt regulation could be successfully used to cultivate plants for the reclamation of coastal saline land in North China.

Urease activity and its relationships to soil physiochemical properties in a highly saline-sodic soil.

To ascertain the levels of urease activities (UA) and their relationships with soil physicochemical properties in salt-affected soils during reclamation, soil transects of a saline-sodic soil with different planting years under drip irrigation were intensively sampled. An enhanced soil UA in root zone (0-40 cm beneath drip emitter) was found as the planting years increased. In all transects, soil UA ranged from 0.38 to 8.53 mu g NH4+-N released g(-1) dry soil h(-1) at 37 degrees C, and showed a large spatial variability within transect. R-2 of multiple regressions increased gradually with planting years, indicating that variations in UA could be better predicted after amelioration. Path analysis showed that the negative direct effects of soil pH on UA were clearly dominant, with the direct path coefficients of -0.357 similar to -0.666 (p < 0.05). Soil organic matter yielded greater positive indirect path coefficients through pH and total nitrogen. An exponential relationship was found between soil UA and pH values (p < 0.01). Our findings demonstrate that after the cultivation under drip irrigation for 3 years, soil biological activities and fertility level increased, with the decrease of soil salinity and sodicity.

Influence of Microsprinkler Irrigation Amount on Water, Soil, and pH Profiles in a Coastal Saline Soil

Microsprinkler irrigation is a potential method to alleviate soil salinization. After conducting a homogeneous, highly saline, clayey, and coastal soil from the Bohai Gulf in northern China in a column experiment, the results show that the depth of the wetting front increased as the water amount applied increased, low-salinity and low-SAR enlarged after irrigation and water redistribution, and the soil pH increased with an increase in irrigation amount. We concluded that a water amount of 207 mm could be used to reclaim the coastal saline soil in northern China.

Effect of different water application intensity and irrigation amount treatments of microirrigation on soil-leaching coastal saline soils of North China

In coastal regions, Bohai Gulf is one of the most affected areas by salinization. To study the effects of mocrosprinkler irrigation on the characteristics of highly saline sandy loam soil (ECe (saturated paste extract)=22.3 dS m−1; SAR (sodium adsorption ratio)=49.0) of North China, a laboratory experiment was conducted. Five water application intensity (WAI) treatments (1.7, 3.1, 5.3, 8.8, and 10.1 mm h−1), five irrigation amount (IA) treatments (148, 168, 184, 201, and 223 mm) and three time periods of water redistribution (0, 24 and 48 h) were employed in the study. A compounding microsprinkler system was used for the WAI treatments, and a single microsprinkler was used for the IA treatments. The results indicated that, as soil depth increased, soil water content (θ) increased and then slightly decreased; with WAI and IA consistently increasing, the relatively moist region expanded and the average θ increased. Meanwhile, soil ECe increased as soil depth increased, and the zone with low soil salinity expanded as WAI and IA increased. Although the reduction of the average SAR was smaller than that of the average electrical conductivity of the ECe, these variables decreased in similar fashion as WAI and IA increased under microsprinkler irrigation. The average pH decreased as soil depth increased. Longer time periods of water redistribution led to lower salinity and slight expansion of the SAR zone. Considering the effects of leached salts in coastal saline soils, greater WAI and IA values are more advantageous under unsaturated flow conditions, as they cause better water movement in the soil. After leaching due to microsprinkler irrigation, highly saline soil gradually changes to moderately saline soil. The results provide theoretical and technological guidance for the salt leaching and landscaping of highly saline coastal environments.

Simple Method for Determining the Emitter Discharge Rate in the Reclamation of Coastal Saline Soil Using Drip Irrigation

AbstractA laboratory experiment was carried out to study the relationships of emitter discharge rate (EDR) and distribution of water and salt for two typical coastal saline soils. The objective was to find a simple method to determine a suitable EDR for reclamation of coastal saline soil using drip irrigation. The experiment included five EDR treatments in a coastal saline sandy-loam soil (SAS): 0.23, 0.55, 0.8, 1.5, and 2.9  L·h−1; another five EDR treatments were conducted in a coastal saline silt soil (SIS): 0.23, 0.55, 1.0, 1.5, and 2.0  L·h−1. The water distribution and the low-salinity zone (with electrical conductivity of the saturated soil extract ≤1, ≤2, and ≤4  dS·m−1) were clearly affected by EDR. The relationships of EDR and wetted front, wetted zone volume, and low-salinity zone were difficult to obtain because of the requirements of determining and calculating the vertical wetted front and the volume of wetted, saturated, and low-salinity zones in the field. For this reason, these relationsh...

Evaluation of methods of nutrient and water management on tea performance and nutrient loss in the Danjiangkou Reservoir area, China

ABSTRACT The long-term control of fertilizer pollution in the Danjiangkou Reservoir is an important task, and promoting good fertilizer pollution control methods is necessary to conserve water quality. A 3-year experiment was conducted to evaluate the fertilizer losses, economic benefits, and feasibility of different nutrient and water management methods in the area. The experiment included the following treatments: (1) local recommended fertilizer dose (450, 144, and 189 kg ha−1 y−1 of N, P2O5, and K2O) under rain-fed conditions (CK); (2) chicken manure at 7500 kg ha–1 without drip irrigation (OF); (3) same dosage of treatment OF but with drip irrigation (OFD); and (4) drip fertigation with 30% of the fertilization dose of CK (DF). The results showed that organic fertilizer and drip fertigation treatments reduced total N (TN) and total P (TP) losses compared to CK due to considerably less amounts of N and P nutrient inputs. Total N runoff losses, and TN and TP concentrations in leaching water did not differ significantly among treatments OF, OFD, and DF. Net income among the CK, OF, and OFD treatments did not differ significantly. Treatment DF resulted in 19.5% and 13.8% more net income than CK and OFD, respectively. Such results provided guidance for promotion to maximize benefits and minimize environmental impacts.