Irrigation Coefficient Research Articles

Hydrochemical assessment of surface water for irrigation purposes and its influence on soil salinity in Tikanlik oasis, China

The assessment of irrigation water quality and the study of its negative influence on soil are very important, because the soil salinization is one of the most important ecological problems. Water quality parameters such as pH, TDS, EC, contents of SO4 2−, Cl−, HCO3 −, CO3 2−, Mg2+, Ca2+, Na+ and K+ in Qiala reservoir were determined. This water is used for the irrigation of the soils in Tikanlik oasis. Monthly water sampling was done in 2007. The analysis indicated that major dominant water type was Na+-Cl−. For the classification of irrigation properties of the water the following chemical indices were calculated: sodium absorption ratio, residual sodium carbonate, sodium percentage, permeability index and irrigation coefficient. The classifications of Wilcox and USDA Salinity Laboratory were also used. The analysis of all classification methods have lead us to the conclusion that there was a low possibility of sodium or alkalinity hazard in the soils irrigated by the water of Qiala reservoir but there was a big salinity hazard. This negative influence was also confirmed by IWQI, through calculation of which the various quality indicators of irrigation water were generalized and represented by a single value. The salinization degree of the soils in the 14 different areas of Tikanlik oasis and the dynamics of its changes during the irrigation period were studied as well. During the irrigation period TDS and EC values increased abruptly in the upper soil horizon. All this led to the accumulation of high quantity of salts in the upper soil horizon during the irrigation season. Continuous monitoring of surface water by IWQI is the effective way for the complex assessment of irrigation water quality as well as for the control of the soil salinization process.

Infiltration Characteristics of Soil Moisture in Liangping County

In order to relieve water shortage, many countries develop water-saving industries and increase water use rate of irrigation. The research on soil water infiltration has important effect on infiltration and runoff, as well as for irrigation. The study carried out in Liangping district of Chongqing by using double ring infiltration method and exploring the reasonable infiltration model in the study area. The relationship of initial soil moisture and irrigation coefficient was studied as well. The results showed that: the Kostiakov empirical formula could simulate the process of soil water infiltration properly. The soil infiltration rate of Liangping is 0.0320cm/min in the selected location.

Application of the Head-Tail Method to Determine Irrigation Coefficient in Hongguang Irrigation District

Irrigation coefficient is not only a critical criterion of the efficiency of agricultural water use, but also an important basis for the evaluation of regional water-saving scheme. According to the Head-tail method (measured net irrigation water use and gross irrigation water use), the irrigation coefficient of Hongguang irrigation district was determined in this paper. The results showed that this method well fitted the real situation of Hongguang irrigation district, and had several advantages including conceptually clear, convenient to use by local staffs. Practical application of this method in irrigation district provides good reference for the future routine evaluation of irrigation efficiency in irrigation.

Irrigation Coefficient Analysis and its Research Progress

Based on the definition of the irrigation coefficient, we discussed the main factors which affect the irrigation coefficient as well as the measures to improve the irrigation coefficient in agriculture. According to the variation and the different features of the irrigation coefficient in different regions and conditions, this article not only explores the basic way to improve the irrigation coefficient, but also gives measures including water apportion measures, management and engineering measures. The potential ability of improving the irrigation coefficient is analyzed preliminarily in the real situation of Chinese irrigation methods and techniques.

Assessment of groundwater quality for irrigation purposes and identification of hydrogeochemical evolution mechanisms in Pengyang County, China

Groundwater is an important water source for agricultural irrigation in Penyang County. Some traditional methods such as irrigation coefficient, sodium adsorption ratio, total alkalinity, total salinity and total dissolved solids were employed to assess groundwater quality in this area. In addition, an improved technique for order preference by similarity to ideal solution model was applied for comprehensive assessment. The origin of major ions and groundwater hydrogeochemical evolution was also discussed. Groundwater in Penyang County contains relative concentrations of dominant constituents in the following order: Na+ > Ca2+ > Mg2+ > K+ for cations and HCO3− > SO42− > Cl− > CO32− for anions. Groundwater quality is largely excellent and/or good, suggesting general suitability for agricultural use. Calcite and dolomite are found saturated in groundwater and thus tend to precipitate out, while halite, fluorite and gypsum are unsaturated and will dissolve into groundwater during flow. Groundwater in the study area is weathering-dominated, and mineral weathering (carbonate and silicate minerals) and ion exchange are the most important factors controlling groundwater chemistry.

EFFECT OF IRRIGATION AND NUTRITION WITH CALCIUM ON FRUIT CRACKING OF THE CAPE GOOSEBERRY (PHYSALIS PERUVIANA L.) IN THE THREE STRATA OF THE PLANT

The cape gooseberry is one of the most important exotic fruit exports from Colombia. The fruits frequently present problems related to cracking that impede their export. Among possible causes of this cracking are irregular irrigation, calcium deficiencies and possibly, the position of fruits on the plant. A randomized complete block design was utilized, where the blocks had irrigation frequencies of 4, 9 and 14 days. A factorial design of 4x3 with a total number of 12 treatments was used, where the first factor was irrigation level (0.7, 1.0, 1.3 and 1.6, measured with a class A Evaporation Pan) and the second factor was calcium dose (0, 50 and 100 kg ha -1 ) on a total of 36 experimental units. Peat moss was utilized as a substrate in 20 L pots. The percentage of fruit cracking was evaluated in the three strata of the plants: I) 90-120 cm, II) 120-140 cm, and III) 140 a 160 cm in height. Significant differences were found among the irrigation levels. An irrigation coefficient of 0.7 resulted in 50% cracked fruits, while with a higher water application (coefficient of 1.6), cracking was found in 17.6% of the fruits. When calcium was not applied, the cracking reached 38%, while with a dose of 100 kg ha -1 , the cracking was 27%. With an irrigation frequency of 14 days, the cracking was 18%, while with irrigation every 4 th day the cracking was 45.6%. The stratum with the highest number of cracked fruits was III (apical) with 38% followed by 37 and 25% for the strata II and I, respectively. The cracking was 81% in the largest fruits and 33% in the small fruits. The lowest fruit cracking occurs separately with the application of 100 kg ha -1 of calcium, an irrigation coefficient of 1.6 and a irrigation frequency of 14 days.

Aridity index as a useful tool for describing impacts of precipitation and temperature regime on maize yield in Vojvodina

Calculated values of aridity index (AI) were used as a base for the analysis of precipitation and temperature impact on maize yield in Vojvodina. An investigation of maize production with irrigation was carried out at the experiment field of Institute of Field and Vegetable Crops in Novi Sad on calcareous chernozem soil on the loess terrace, in the period 1997-2007. Standardized values of temperatures (T') and precipitation (P') were used for AI calculation. Highly significant correlation (r = 0.86**) was found between AI and average yields of maize in Vojvodina. There were no significant correlations between AI and maize yield obtained in field experiments without irrigation (r = 0.40) and with irrigation (r = -0.24). Low values of correlation coefficient between AI and maize yields obtained in field experiments without irrigation and correlation coefficient values between AI and average yields of maize in Vojvodina indicate that production technology of maize in Vojvodina could be improved. Higher values of maize yield in irrigation conditions than in conditions without irrigation (20% or 2.04 t ha-1) confirm justification of maize production with irrigation under climatic conditions of Vojvodina.

Quantifying bioirrigation using ecological parameters: a stochastic approach†.

Irrigation by benthic macrofauna has a major influence on the biogeochemistry and microbial community structure of sediments. Existing quantitative models of bioirrigation rely primarily on chemical, rather than ecological, information and the depth-dependence of bioirrigation intensity is either imposed or constrained through a data fitting procedure. In this study, stochastic simulations of 3D burrow networks are used to calculate mean densities, volumes and wall surface areas of burrows, as well as their variabilities, as a function of sediment depth. Burrow networks of the following model organisms are considered: the polychaete worms Nereis diversicolor and Schizocardium sp., the shrimp Callianassa subterranea, the echiuran worm Maxmuelleria lankesteri, the fiddler crabs Uca minax, U. pugnax and U. pugilator, and the mud crabs Sesarma reticulatum and Eurytium limosum. Consortia of these model organisms are then used to predict burrow networks in a shallow water carbonate sediment at Dry Tortugas, FL, and in two intertidal saltmarsh sites at Sapelo Island, GA. Solute-specific nonlocal bioirrigation coefficients are calculated from the depth-dependent burrow surface areas and the radial diffusive length scale around the burrows. Bioirrigation coefficients for sulfate obtained from network simulations, with the diffusive length scales constrained by sulfate reduction rate profiles, agree with independent estimates of bioirrigation coefficients based on pore water chemistry. Bioirrigation coefficients for O2 derived from the stochastic model, with the diffusion length scales constrained by O2 microprofiles measured at the sediment/water interface, are larger than irrigation coefficients based on vertical pore water chemical profiles. This reflects, in part, the rapid attenuation with depth of the O2 concentration within the burrows, which reduces the driving force for chemical transfer across the burrow walls. Correction for the depletion of O2 in the burrows results in closer agreement between stochastically-derived and chemically-derived irrigation coefficient profiles.

Biological enhancement of solute exchange between sediments and bottom water on the Washington continental shelf

Solute exchange between the interstitial waters and overlying waters on the Washington continental shelf was investigated based on measurements of the pore-water sulfate distribution and sulfate reduction rates as well as through models describing the distribution of sulfate in anaerobic pore waters. The depth-integrated sulfate reduction rate greatly exceeded the influx of sulfate attributable to molecular diffusion and sediment accumulation acting on the measured vertical sulfate gradients, and indicated that additional transport mechanisms must have been operating. Sediment mixing was probably not the primary mechanism since high eddy diffusivities would be required to depths of 30 cm to maintain the observed sulfate distribution, whereas previously measured 210Pb distributions indicated sediment mixing is primarily restricted to depths <7 cm. Irrigation of bottom water through animal burrows was the most likely mechanism. To describe this process, a general diffusive irrigation coefficient, B, was formulated. Vertical profiles of B showed the main irrigation zone occurred between 2 and 10 cm with reduced irrigation rates occurring below this. These coefficients calculated from the sulfate distribution were similar to ones calculated from previously published radon measurements at the same stations, indicating that this formulation of irrigation exchange may be useful in modelling the exchange of dissolved solutes between the pore water and the bottom water.

Blood flow in thigh muscle during bicycling exercise at varying work rates

16 male subjects exercised at 25, 50, 75, 90, 100 and 120% of VO2max on a von Döbeln bicycle ergometer. The muscle mass was measured in a whole body counter. Muscle blood flow (MBF) estimated from the rate of 133Xe clearance from m. rectus femoris showed a levelling-off at about 0.5 1 of blood per min and liter of muscle tissue (equal to an irrigation coefficient of 0.5 min-1) at work rates above 50 to 60% of VO2 max. This concurs with clearance data from the literature. However, when MBF is calculated from VO2, muscle mass, and reliable values for a- vo2 differences, MBF in the present subjects would: 1. Not level off before 90 to 100% VO2max, 2. reach a value of 1.0 min-1. The underestimation of MBF calculated from 133Xe clearance and the levelling-off shown by this method may be due to a systematic error inherent in the method, the 133Xe clearance being diffusion limited at high flow rates.