1Assistant Professor and Extension Agricultural Engineer, Kansas State University, USA
2Associate Professor and Natural Resources Engineer, South Dakota State Univ, USA
3Professor and Extension Agricultural Engineer, Kansas State
The results from the first year of a field study on suitability of using subsurface drip irrigation for alfalfa provided some answers to producers in western Kansas. The treatments in the study included placement of drip tapes at (a and b) 1.5 m spacing with 0.46 m and 0.30 m depths, (c and d) 1.0 m spacing with 0.46 and 0.30 m depths, (e) 0.76 m spacing with 0.46 m depth, and (f) a center pivot sprinkler irrigated plot seeded to alfalfa at the same time. Emergence of seedlings was affected adversely at the 1.5 m spacing and showed "striping". During the hot dry cycles in the growing period, one could visualize the location of drip tapes at the 1.5 m spacing from the color and bloom setting of the plants farthest from the tape. The first harvest of the season yielded the most. Hay yield for the harvest obtained for the period of regrowth from late June to late July was lower for the treatment with 1.5 m spacing at the 0.46 depth. Total yields for the year were reduced slightly for the 1.5 m spacing. The two depths of placement (0.46 and 0.30 m) produced similar yields.
1 Kansas State University, 105 Experiment Farm Road, Colby, Kansas 67701-1697, USA
2 South Dakota State University, Box 2120, Brookings, South Dakota 57007-1496, USA
Kansas State University initiated studies in 1989 to develop the methodology for successful application of subsurface drip irrigation (SDI) for corn production on the deep silt loam soils of the Central Great Plains, USA. Irrigation water use for corn can be reduced from 35 to 55% when using SDI compared to more traditional forms of irrigation in the region. Irrigation frequency has not been a critical issue when SDI is used for corn production on the deep silt loam soils of the region. A dripline spacing of 1.5 m has been found to be most economical for corn grown in 0.76 m spaced rows. Nitrogen fertigation was a very effective management tool with SDI, helping to maximize corn grain yield yields, while obtaining high efficiencies of nitrogen and water use. The research SDI systems have been utilized since 1989 without replacement or major degradation. SDI systems lasting 10-20 years are cost competitive for corn production with the more traditional forms of irrigation in the Great Plains for certain field sizes and water constraints.
1 Water Management Research Laboratory, USDA-ARS, Fresno CA 93727, USA
2 University of California, Kearney Agricultural Center, Parlier CA, USA
3 SDI, Clovis, CA
4 United Agri Products, P O Box 2357, Fresno CA 93745-2357, USA
A four year experiment was conducted using a large weighing lysimeter to determine the crop coefficient and crop water use of a late season peach cultivar irrigated with a surface drip system. Two trees were planted in a 2 m by 4 m by 2 m deep weighing lysimeter that was surface irrigated with 2 L/hr in-line drip emitters. Irrigation was applied in 12-mm applications after a 12-mm water loss threshold was exceeded as measured by the lysimeter. The crop coefficient (Kc) was calculated using the measured water losses and grass reference evapotranspiration calculated using the CIMIS Penman equation. The Kc was plotted against the day of the year and linear, quadratic, and cubic regressions were fit to the data. A three segment linear and the cubic equation had the best fit to the data. The maximum Kc determined for the linear fit in this experiment was 1.06 compared to a maximum of 0.92 recommended for use in California and 0.98 calculated using the FAO method. Average water use for the 4 years of the experiment was 1034 mm.
LI GUANGYONG1, HUANG XINGFA1, WANG XIAOWEI2
1 China Agricultural University, Beijing, 100083, China
2 Beijing Horticulture Research Institute, Beijing, 100093, China
Peach trees grown on a clay loam soil, were irrigated under 2 different treatments: 80% of E-pan all seasons (full irrigation treatment) and 20% of E-pan (Regulated Deficit Irrigation - RDI) during slow fruit growth stage plus 80% of E-pan during the rest periods. Compared with full irrigation, RDI treatment saved 20% of water and kept almost same yield and shoot growth reduced. Similar results were obtained for all years of the study. The annually averaged crop factors were 0.474 and 0.378 for full irrigation and RDI treatment, respectively.
Due to warm climatic conditions in autumn, leaf fall of grapevines along the Lower Orange River region in South Africa occurs relatively late compared to the cooler coastal regions of the Western Cape. However, there is uncertainty about the transpiration efficiency of grapevine leaves and its contribution to evapotranspiration during this period. The aim of this study was to relate whole canopy transpiration of Sultanina grapevines to leaf area. To achieve this, sap flow and leaf area index (LAI) of drip as well as micro sprinkler irrigated grapevines were measured at Augrabies during various phenological phases. Transpiration efficiency (TE) was obtained by dividing sap flow rate by total leaf area as calculated from LAI measurements. TE was highest during spring and decreased as leaf layers, and consequently shading of leaves within the canopy increased. Although leaf area remained high, TE decreased during late summer and autumn as leaves began to age. Transpiration was almost insignificantly low prior to leaf fall. Hence, under the given conditions, leaves remaining on grapevines during autumn and prior to leaf fall did not contribute significantly to evapotranspiration. In the case of drip irrigation, total transpiration per grapevine was lower in comparison to that of micro sprinkler irrigated ones. This was mainly due to smaller leaf area of drip irrigated grapevines. However, compared to micro sprinkler irrigation, TE of the drip irrigated grapevines tended to be higher due to their less dense canopies. It was concluded that irrigation management rather than the system itself resulted in the tendency towards higher TE.
Onions are a major irrigated crop in New Mexico. An excessive amount of water is generally applied, because the crop is shallow-rooted and requires frequent irrigation to achieve good yields. Onions under deficit irrigation have a decrease in evapotranspiration and yield. Consequently, farmers need to use the water production function (wpf) for onions to estimate water requirements at different locations for selected yield goals. The wpf is the relationship between yield and water applied. The same relation can be expressed in terms of evapotranspiration, in which case the production function is known as the evapotranspiration production function (Etpf). A gradient sprinkler line source onion experiment was conducted in 1986 and 1987 at Farmington New Mexico and a linear Etpf determined. A second gradient drip line- source irrigation experiment was conducted at Las Cruces, M. M. during 1994-1995 to determine a wpf as related to applied water for drip irrigated onions. The irrigation treatments were 40, 60, 80, 100, and 120 % of calculated non -stressed evapotranspiration determined from the sprinkler line source experiment . The wpf was curvilinear because excess water was applied to the different irrigation levels in the experiment in order to keep the base plate of the onions wet so root growth would continue. The result was that part of the applied water went to deep drainage rather than to evapotranspiration. The wpf was corrected for the amount of irrigation water lost as deep drainage and expressed as evapotranspiration versus yield (Etpf) by using reference evapotranspiration measured at Las Cruces and season crop coefficients for selected yield levels measured at Farmington N.M. Maximum onion yield at Las Cruces under the drip irrigation system was 26% higher than measured at Farmington NM using the sprinkler system. The results indicate that high onion yield are achievable using a drip system compared to a sprinkler system but a larger amount of applied water goes to deep drainage using a drip system compared to a sprinkler system to achieve maximum yield.