Premium
A Geostatistical Approach to the Trickle Irrigation Design in a Heterogeneous Soil 2. A Field Test
Author(s) -
Russo David
Publication year - 1984
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1029/wr020i005p00543
Subject(s) - drip irrigation , irrigation , yield (engineering) , hydraulic conductivity , soil science , soil water , environmental science , mathematics , hydrology (agriculture) , soil gradation , agronomy , geology , geotechnical engineering , physics , biology , thermodynamics
In a heterogeneous field in which the soil water properties vary under a “deterministic” uniform trickle irrigation system, the midway soil‐water pressure head h c and the yield of a crop also differ from place to place. These differences may, in turn, reduce the average (over the field) yield relative to the yield that would be obtained if the soil was uniform throughout the field. A field experiment was conducted to test the hypothesis that this yield reduction may be eliminated by using a spatially variable trickle irrigation system. Twenty‐five plots (200 m 2 each) were established on a 30‐m 2 grid. Half of each plot was equipped with a standard trickle irrigation system with constant spacing between emitters of d = 50 cm (control plots), and the other half was equipped with a trickle irrigation system for which the spacing between the emitters was selected by using the pertinent hydraulic properties (the saturated hydraulic conductivity K s and the soil parameter α) according to the procedure of Bresler (1978) as described in paper 1 (Russo, 1983 b ). Values of h c measured at different times, as well as the total fruit yield Y of bell pepper ( Capsicum frutescens var. “Maor”), were used to estimate the seasonal and the spatial distributions of h c and the spatial distribution of Y and their moments. The variograms of h c and Y were calculated and used to estimate their integral scales. It was found that the use of a spatially variable d relative to the use of a uniform d did not change the seasonal behavior of hc but reduced the spatial variability in h c and Y by 35% and 11%, respectively, and increased the integral scale of h c and Y by 30% and 10%, respectively, but increased the average total fruit yield by only 1.9%. The use of a spatially variable d reduced the dependence of Y on h c . This indicates that when the emitters are properly spaced, it is not the water but other factors that most influence yield. When a constant d was used, the dependence of Y of h c decreased with time. This and the relatively good agreement between the values of h c measured at the initial stages of the growing season and those calculated in paper 1 demonstrate that the concept of h c is important in the early stages of the plant's growth, when the root system is not fully developed. Both the theoretical (paper 1) and the experimental results showed that although K s and α, as well as h c , varied considerably in the field the spatial variability of the crop yield was relatively small. This explains why the use of a spatially variable d essentially was not an improvement over the fixed d . It is suggested that this study will be considered as a methodological one, which can be adapted to solve practical problems associated with field spatial variability.