1Department of Plant Production and Soil Science, University of Pretoria, Pretoria, 0001 South
2Decagon Devices Inc, P O Box 835, Pullman, Washington 99163, USA
3Department of Soil Science, University of the North, Private Bag X1106, Sovenga, 0727 South Africa
4NB Systems, P O Box 15102, Sinoville, 0129 South Africa
Distribution of water and energy is non-uniform in widely spaced, micro-irrigated crops. For accurate water use predictions, this two-dimensional variation in the energy and water balance must be mechanistically described. To this end, a user-friendly, 2-D soil water balance model (SWB-2D), has been developed. Energy is partitioned at the surface depending on solar orientation, row direction and canopy size, shape and leaf area density. Water is distributed uniformly at the surface in the case of rainfall, whilst micro-irrigation only wets a limited portion of the field. Crop water uptake is calculated as a function of evaporative demand, soil water potential and root density. Evaporation is also calculated as being either limited by available energy or by water supply. Water is redistributed in the soil in two-dimensions with a finite difference solution to the Richards’ equation. Two field trials were set up in order to validate the 2-D soil water balance model, one in a peach orchard at Hatfield (Pretoria, South Africa), and the other in a citrus orchard at Syferkuil (Pietersburg, South Africa). Model predictions compared well to actual soil water content measured with time domain reflectometry probes. The model holds tremendous potential for improved irrigation scheduling through increased accuracy in estimated soil water reserves, since it accounts for the differing conditions which occur in the under-tree strip and inter-row area.
Department of Agro-forestry Engineering, University of Lleida, Lleida, Spain
Department of Biosystems Engineering, University of Hawaii, Honolulu, Hawaii, 96822, USA
The efficient water use by microirrigation can be evaluated by the total return. An optimal irrigation schedule was determined through an economic analysis using the cost of water, price of yield, uniformity of the microirrigation system, crop response to water application and environmental concerns of pollution and contamination. The optimal irrigation schedule can achieve optimal return and also provide water saving compared with the conventional irrigation schedule in which the whole field is fully irrigated.
* Faculty of Agriculture, Ain Shams University, Box 68 Hadiak Shoubra 11241, Cairo, Egypt
** Water Research Center, Box 6 El-Kanater, Kalubia 13621, Egypt
The study was conducted through 1994 and 1995 seasons on three years old Anna apple trees budded on MM 106 grown in sandy soil to study the effect of different irrigation treatments on water use, crop factor (Kc),water use efficiency and cost benefits. The effect of irrigation levels on vegetative growth of trees, yield and fruit quality attributes was also determined. The results indicated that the water use of “Anna” apple trees were 202.2, 304.3 and 406.8 mm for 1994 and 215.3, 321.2 and 427.2 mm for 1995 season for the FO.4, FO.6 and FO.8 treatments respectively. Crop coefficient (Kc) ranged from 0.43 to 0.67 for the development period, from 0.67 to 0.69for the mid and from 0.69 to 0.53 for the late season. Water use efficiency was highest for irrigation treatment FO.4. Water saving reached approximately 48%. Net benefit was obtained theoreticaly from soil water applied according to FO.9 under normal farming conditions.
Increasing the amount of irrigation water considerably increased the annual percentage increase of trunk diameter, shoot length, fruit diameter and decreased the annual percentage increase in the number of shoots per branch in the two studied seasons. The highest irrigation level FO.8 gained the greatest average fruit weight and the highest yield compared with the two lowest irrigation treatments for the two seasons respectively. Water stress treatment FO.4, however, decreased tree yield and significantly, increased fruit firmness, skin coloration and percentage total soluble solids in fruit pulp.
1KULeuven, Institute for Land and Water Management, Vital Decosterstraat 102, B-3000 Leuven, Belgium
² KULeuven, Hydraulics laboratory, W de Croylaan 2, B-3001 Heverlee, Belgium
Fertilized cropland is a potential non-point source of nitrogen contributing to the nutrient enrichment of surface water ecosystems. Nitrogen is present in drainage outflow primarily because of the addition of fertilizers. The purpose of this study is to model the nitrate leaching to surface waters using a quasi two-dimensional mechanistic flow model (DRAINMOD) in combination with a GIS. The GIS is used to describe for the catchment the spatial distribution of soil type and land use, and to present the calibrated nitrate leaching over the catchment. This paper summarizes the method used to model the nitrate leaching at field scale and how the GIS was applied to present the spatial distribution of nitrogen loss by natural and artificial drainage. The method was applied to the Witte Nete catchment in Belgium having a total catchment area of 40.7 km2. The study shows great advantages of the association between a GIS and a nitrate simulating model where spatial data management, taken care of by the GIS, is combined with temporal variable calibration, taken care of by the mechanistic model. Furthermore, the study illustrates that a GIS in combination with a mechanistic field scale model is a powerful and suitable tool for modeling and analyzing nitrate leaching at catchment scale. The resulting vulnerability map depicts the nitrogen leaching as a function of soil type and land use and gives the decision maker the opportunity to diversify the nitrogen leaching standards.
Department of Agrometeorology, University of Orange Free State, Bloemfontein, South Africa
Micro-irrigation is generally considered to have higher application efficiencies than other forms of surface or sprinkler irrigation. However, frequently the droplets emitted by micro-jets or micro-sprinklers are very small and thus the influence of ambient weather conditions during an irrigation application event should have a major effect on efficiency. This study investigated the effect of different sets of weather variables on the amount of water lost by evaporation when applying micro-irrigation to a grass surface. A sensitivity analysis was performed for each variable. The Penman-Monteith equation and current weather data (including solar radiation, Relative humidity, air temperature and wind speed) were used to calculate atmospheric evaporative demand (AED). Doubling the wind speed and air temperature resulted in increases of 60% and 20% in AED respectively. A field experiment was performed to measure these losses. A typical micro-sprinkler was used and the water flow and pressure was regulated and monitored. The sprinklers were set 350 mm above the ground and had a passive 360° spreader. The amount of water reaching the soil surface was measured in catch pans. The water losses were calculated by measuring differences between water flowing into, and water leaving the system. Irrigators can use the results to make decisions concerning the desirability of weather conditions during micro-irrigation.
Department of Irrigation and Drainage Engineering, College of Technology,
G B Pant University of Agriculture and Technology, Pantnagar, India
Field experiments were conducted to study the response of three irrigation moisture regimes corresponding to 100, 80 and 60 percent of crop water requirement, applied through drip irrigation system and one level (100% ) for surface method of irrigation in combination with 25 micron black plastic mulch on Tomato for two years ( 1995-96, 96-97 ) at Horticulture Research Centre, G.B. Pant University of Agriculture and Technology, Pantnagar ( India ). The site is located at 243.8 m altitude, 290 N latitude and 79.30 E longitude, in humid subtropical climate and a sandy loam soil in northern India. The study indicated that the components of biometric yield such as plant height, leaf area were maximum for the treatment irrigated with drip system combined with plastic mulch and minimum for the control ( surface irrigation at 100% moisture regimes without mulch ) treatment. The marketable fruit yield was found to be maximum as 94.85 t/ha from the treatment irrigated with drip system combined with mulch at 80% moisture regimes. The yield of other treatments varied from 55.19 to 82.55 t/ha and found to be lowest ( 39.10 t/ha ) in control treatment. The highest water use efficiency (3.36 t/ha-cm) was obtained for the treatment irrigated with drip system in combination with plastic mulch at 60% moisture regimes and lowest 0.76 t/ha-cm for the control treatment. When water saving vegetable growth, yield and economics return were taken into account, then an irrigation level of 80% through drip system along with plastic mulch may be considered optimal.
Department of Plant Production and Soil Science, University of Pretoria, Pretoria,
0002 South Africa
Borehole water with salt (NaCl) concentrations ranging between 4-26 mM L-1 has been used for irrigation during summer in some regions of Botswana. Experiments were conducted under field conditions at the Hatfield Experimental Farm of the University of Pretoria using 1-2 year-old potted trees. Stem water potential (covered leaves) and stomatal conductance were measured at midday (Rmd 10.0pt;mso-bidi-font-family:Arial'>) of two rootstocks (Rough Lemon and Swingle) using the cultivar ‘Late Valencia’ as scion. Trees were irrigated with saline water having different salt concentrations (Na, Cl, and a combination of NaCl) applied as NaSO4 and CaCl2 and their combination, respectively, in the range of 4-26 mM L-1 when the threshold of soil matric potential of 30 KPa was reached. At midday, stem water potential was significantly lower in the Swingle rootstock in contrast to the Rough Lemon and the controls indicating that the Rough Lemon rootstock was apparently more salt tolerant than Swingle. No significant differences in stomatal conductance were observed, when Swingle and Rough Lemon rootstocks were exposed to salt stress. Na and Cl concentrations of plant organs and soils showed that the rootstock stem of Rough Lemon accumulated significantly higher levels of chloride and sodium than the Swingle rootstock stem. The high salt accumulations in Rough Lemon might indicate that the rootstock prevented salts to be accumulated in the leaves which would likely lead to reduced photosynthetic rates.
1Assistant Professor, Agriculture Research Station, Gangavati-583 227,Karnataka (India)
2 Professor and 3 AICTE Emeritus, Dept.of Irrigation & Drainage Engineering , GBPUAT, Pantnagar, UP (India)
Investigations were carried out to study the effect of microsprinkler and surface irrigation methods on water economy, growth and yield of cowpea at HRC, Pantnagar during 1997 and 1998. The crop was grown as a intercrop in between the rows of sweet lime. Irrigation requirement was met based on depletion in available soil moisture and ET of the crop for surface and microsprinkler irrigation, respectively. Results indicated that higher grain yield of cowpea (12.6 q/ha) was recorded for microsprinkler irrigation as against 9.9 q/ha in surface methods of irrigation. Significant improvements in biometric growth and yield parameters were recorded for microsprinkler irrigation as compared to surface irrigation. Significant saving of water (20.9 %) was achieved for microsprinkler irrigation resulting in higher water use efficiency of 37.9 kg/ha-cm as against 24.3 kg/ha-cm in case of surface irrigation. The gross BC ratio of 1.44,1.54 and 2.00 were achieved for surface irrigation, microsprinkler irrigation considering with system cost and microsprinkler irrigation considering without system cost, respectively. The net profit achieved per cm application of irrigation water used was highest in case of microsprinkler irrigation considering without system cost (Rs.601) followed by microsprinkler irrigation considering with system cost (Rs.418) and lowest in case of surface irrigation (Rs.210).
1 Faculty of Agriculture, Kyushu University, 394 Tsubaguro, Sasaguri, Kasuya, Fukuoka 811-2415 Japan
2 Arid Land Research Center, Tottori University, 1390 Hamasaka, Tottori 680-0001 Japan
Mulches have been used to modify microenvironment of agricultural fields since ancient times. In the 20th century, various chemical mulches such as polyvinyl chloride films and polyethylene films have been developed and widely used over the world. However, near the entrance of the 21st century, they have been criticized because they are difficult to dispose and cause waste problems. In Japan, recycled paper mulches have been gradually adopted to paddy field cultivation to prevent weeds, and gained a good reputation. Recently, recycled paper mulches for non-paddy fields have been developed and examined from several aspects. In this study, modifications of microclimate and soil moisture by the recycled paper mulch, an emboss-mulch, were examined. The results show that the recycled paper mulch had large albedo and high retentivity of soil water thus reduced the soil temperature fluctuation (cool in daytime and warm in night time) and kept the upper soil moist. These effects gave preferable condition for vegetable growth and enhanced the effectiveness of irrigation. Since recycled paper mulches can be directly disposed in fields without harm to the environment, it should be useful tool for the sustainable agriculture in combination with micro irrigation.
1Irrigation and Drainage Section, Faculty of Agronomy, University of Buenos Aires, Argentina
2Irrigation and Drainage Section, Faculty of Agricultural Science, University of Jujuy, Argentina
During the last fifteen years, a great increase was seen in the area of intensive crops of citrus and subtropical crops, irrigated with trickle systems (drip and minisprinkler) in the northern area of Argentina. The source of water, for these can be at the surface level and/or at the sub-surface level, depending on the location of the different facilities. Systems of micro-irrigation require the study of the physic and chemical characteristics of the water to be utilized, in order to thoroughly define the necessary filters for the equipment (Nieberck, A.S. 1995). In this case the only available water was that in the surface level, coming from Rio Bermejo, with up to 26860 p.p.m. of suspended solids. This situation happens during the Summer, when rainfalls occur in the range of 800 mm (SMN 1986). When these occur at another point of the basin, we need to find out appropriate tools in order to obtain water with physical characteristics compatible with the emitting devices of the systems. In this case we have taken the following steps: 1. Determination of an appropriate point to locate the pump, at a straight section of the river; 2. Installation of decanters, in order to separate sand materials; 3. Passing through a dam in order to permit decantation of thinner material; 4. Re-pumping and filtration with group of gravel filters and circulating water screen filters; 5. Periodical cleaning treatments with phosphoric acid, in order to prevent algae clogging. After ten years, the dripping system is operative with its original drippers, with flows compatible with those designed.
 Dept of Soil and Water Sciences. Faculty of Agricultural, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem
2Arava Research and Development, Mobile Post Eilot 88820, Israel
Micro-irrigation enables the increase of irrigation frequency from weeks to daily or even shorter time periods, and enables management of soil water so that conditions of relatively high water content can be maintained. Discrete water application outlets give rise to a non-uniform but well ordered spatial pattern of water distribution. The spatial fluctuations in water content enable plants to concentrate roots in and extract water from zones where water content is higher than field capacity, without the growth inhibiting effects of poor aeration. We hypothesize that augmented mass flow in the soil caused by the high water content found in high-frequency irrigation regimes increases water availability due to higher water potential and hydraulic conductivity.
Sunflower (Helianthus annuus) was grown in two sizes of lysimeters and irrigated with equal quantities of total water given at different frequencies. High-frequency irrigation resulted in greater water consumption and greater yields. Continuous irrigation resulted in even greater growth than irrigation consisting of 8 pulses per day. The positive effect of high-frequency irrigation was found for systems with one-dimensional wetting patterns as in flood or sprinkler methods as well as for systems with radial distribution patterns as with drip irrigation.
Department of Irrigation and Drainage Engineering, College of Technology, G B Pant University of Agriculture and Technology, Pantnagar, India
Studies were conducted on yield corresponding to irrigation water applied and economics of drip irrigation installation for mango (Mangifera Indica) in Western Uttar Pradesh and around Hydrabad region of Andhra Pradesh (India). The studies were based on field survey of farmers, information from industries and regional climate data besides analysis of actual installation of drip irrigation system at the farmers field. Analysis of the survey shows that the yield of mango varied from 24 to 83 t/ha for 6 to 30 years age of crop in Western Uttar Pradesh and 20.4 to 29.38 t/ha for 4 to 6 years age of mango orchard in Hydrabad region respectively. The volume of water applied per year per hectare varied from 2267.40 to 5882.7 m3 for1 to 30 year mango orchard in western Uttar Pradesh and 1549.66 and 3717.80 m3 for 4 to 6 years group of mango trees in Hydrabad region respectively. The average initial cost of drip system varied from Rs. 30560 (US $ 728) to Rs. 35720 (US $ 850) per hectare. The net cash inflow for 10 years was found to be Rs. 1047752 (US $ 24709) and Rs. 1129347 (US $ 27037) in Western Uttar Pradesh and Hydrabad region respectively.
Department of Irrigation and Drainage Engineering, College of Technology, G B Pant University of Agriculture and Technology, Pantnagar, India – 263145
Field experiments were conducted in an area of 240 m2 from February to July 1993 at the Horticulture Research Centre of G.B. Pant University of Agriculture and Technology, Pantnagar ( India ) to study the performance of microsprinkler, drip microtube, drip emitter and surface methods of irrigation on biometric yield of chilli crop (Capsicum annum L.) cultivar Pant C-1. The site is located at 243.8 m altitude, 290N latitude and 79.30E longitude in humid subtropical climate and a sandy loam soil in Northern India. The study indicated that the percentage increase in plant height (90 days after first measurement) were 7.1, 5.64 and 1.08 for drip microtube, microsprinkler and drip emitter irrigation treatment respectively, compared to surface irrigation. The effect of irrigation treatment was found to be not significant for plant height of chilli plants. The percent increase in number of branches compared to surface method was 6.88, 5.35 and 4.57 for microsprinkler, drip microtube and drip emitter respectively, which also showed statistically not significant effect of irrigation treatments. The percent increase of leaf area compared to surface irrigation was 14.5 and 7.2 for microsprinkler and drip microtube irrigation treatments respectively, and found statistically significant.
Institute of Production Engineering and Farm Buildings Research, Federal Research Centre of Agriculture (FAL), Bundesallee 50, D-38116 Braunschweig, Germany
The aim of this article is to point out the chances for a method-specific reduction of the water- and energy input in irrigation of agricultural and horticultural crops. A brief analysis of the common irrigation methods is given and proposals are made for further technical development towards an increase in water- and energy efficiency of mobile and semi-mobile irrigation machines. the proposed concept of mobile drip irrigation is applicable to both, the boom trailer irrigation and the centre pivot or linear move machines. The main characteristics values for the selection of a proper system are given together with the empirical appraisal of their applicability.