The effects of applied water at various fractions of measured evapotranspiration on water relations and vegetative growth of Thompson Seedless grapevines

Vegetative growth and water relations of Thompson Seedless grapevines in response to applied water amounts at various fractions of measured grapevine ET_c were quantified. Treatments ranged from no applied water up to 1.4 times the water used by vines growing in a weighing lysimeter. All treatments were irrigated at the same frequency as the vines in the lysimeter (whenever they used 2 mm of water), albeit at their respective fraction. Soil water content and midday leaf water potential (Ψ_l) were measured routinely in four of the irrigation treatments across years. The amount of water depleted in the soil profile ranged from 190 mm for the 0.2 treatment in 1993 to no water depletion for the 1.4 treatment in 1992. The irrigation treatments significantly affected midday Ψ_l, total shoot length, leaf area per vine, pruning weights and trunk diameter; as applied water decreased so did vegetative growth. Pruning weights were a linear function of the seasonal, mean midday Ψ_l across growing seasons. The application of water amounts in excess of evapotranspiration negatively affected vegetative growth some of the years. A companion paper will demonstrate that over-irrigation can negatively affect reproductive growth of this grape cultivar due to excess vegetative growth.     

Water use of mature Thompson Seedless grapevines in California

Water use of Thompson Seedless grapevines was measured with a large weighing lysimeter from 4 to 7 years after planting (1990-1993). Above-ground drip-irrigation was used to water the vines. Vines growing within the lysimeter were pruned to four and six fruiting canes for the 1990 and 1991 growing seasons, respectively, and eight fruiting canes in the last 2 years. Maximum leaf area per vine at mid-season ranged from 23 to 27 m² across all years. Reference crop evapotranspiration (ET_o) averaged 1,173 mm between budbreak and the end of October each year, with a maximum daily amount of approximately 7 mm each year. Maximum daily vine water use (ET_c) was 6.1, 6.4, 6.0, and 6.7 mm (based upon a land area per vine of 7.55 m²) for 1990, 1991, 1992, and 1993, respectively. Seasonal ET_c was 718 mm in 1990 and ranged from 811 to 865 mm for the remaining 3 years of the study. The differences in water use among years were probably due to the development of the vine's canopy (leaf area), since they were pruned to differing numbers of fruiting canes. These differences were more pronounced early in the season. Soil water content (SWC) within the lysimeter decreased early in the growing season, prior to the initiation of the first irrigation. Once irrigations commenced, SWC increased and then leveled off for the remainder of the season. The maximum crop coefficient (K_c) calculated during the first year (1990) was 0.87. The maximum K_c in 1991, 1992, and 1993 was 1.08, 0.98, and1.08, respectively. The maximum K_c in 1991 and 1993 occurred during the month of September, while that in 1992 was recorded during the month of July. The seasonal K_c followed a pattern similar to that of grapevine leaf area development each year. The K_c was also a linear function of leaf area per vine using data from all four growing seasons. The decrease in K_c late in the 1991, 1992, and 1993 growing seasons, generally starting in September, varied considerably among the years. This may have been associated with the fact that leafhoppers (Erythroneura elegantula Osborn and E. variabilis Beamer) were not chemically controlled in the vineyard beginning in 1991.     

Effect of high frequency surface and subsurface drip irrigation on root distribution of sweet corn

Summary Characterization of root growth and distribution is fundamental in explaining crop responses to irrigation and in determining appropriate management of irrigation systems, particularly with drip systems since it is widely believed that drip irrigation may limit the extent of root development. An experiment was conducted to study root distribution of sweet corn grown under high frequency surface (S) and subsurface (SS) drip irrigation, fertilized daily through drip systems at three phosphorus levels of P₀ (no injected P), P₁ (P injected at 67 kg/ha) and P₂ (P injected at 134 kg/ha). Root sampling at the end of the growing season indicated that: (1) Root extension continued at depths in excess of 2 m in both the surface and subsurface drip at all P levels. (2) The greatest differences between SS and S treatments were observed in the top 45 cm depth. Higher root length density was observed in the surface 30 cm in S plots while the sweet corn in the SS plots had greater root length density than S plots below 30 cm, and (3) the greater root length density in the SS irrigated sweet corn was not reflected in a similar increase in total above-ground dry matter.This project was partially supported by a grant from BARD Project no I-1116-86     

Water-nutrient-herbicide management of potatoes with trickle irrigation

A study was designed to test the effectiveness of nitrogen and herbicide applications through soil moisture-controlled, trickle-irrigation systems, and to test the effectiveness of automatic irrigation via soil moisture control to minimize the water requirement and N-losses for high-frequency, trickle-irrigation systems. Results indicated that single or multiple applications of herbicide at recommended rates can be used effectively with trickle irrigation to control weeds in the potato row where cultivation is not possible. Nitrogen can be efficiently applied through a trickle system that features automatic soil moisture control through the use of a high-frequency irrigation schedule.     

Water use by drip-irrigated late-season peaches

A 4-year experiment was conducted using a large weighing lysimeter to determine the crop coefficient and crop water use of a late-season peach cultivar (Prunus persica (L.) Batsch, cultivar O'Henry) irrigated with a surface drip system. Two trees were planted in a 2×4×2 m deep weighing lysimeter that was surface irrigated with ten 2 L/h in-line drip emitters spaced evenly around the trees. Irrigation was applied in 12 mm applications after a 12 mm water loss threshold was exceeded as measured by the lysimeter. The crop coefficient (K_c) was calculated using the measured water losses and grass reference evapotranspiration calculated using the CIMIS Penman equation. K_c was plotted against day of the year and linear, quadratic, and cubic regressions were fitted to the data. A three-segment linear and the cubic equation had the best fit to the data. The maximum K_c determined for the linear fit in this experiment was 1.06 compared with a maximum of 0.92 recommended for use in California and 0.98 calculated using the FAO method. Average annual water use for the 4 years of the experiment was 1,034 mm. Mid-day canopy light interception was found to be well correlated with the crop coefficient determined using the lysimeter data.Communicated by P. Thorburn     

Soil water variability under subsurface drip and furrow irrigation

Non-uniformities in soil hydraulic properties and infiltration rates are considered to be major reasons for the inefficiencies of some surface irrigation systems. These non-uniformities may cause non-uniformities in soil water contents and could potentially affect plant growth. To investigate whether the non-uniformities in soil water contents can be overcome by well-managed irrigation systems, fields with clay loam soils and planted to cotton were irrigated with a continuous-flow, a surge flow, and a subsurface drip system. Measurements of water contents in each field were taken throughout the growing season at several depths. The water contents measured within the top 0–0.9 m in the three irrigations systems were evaluated in terms of their spatial and temporal variabilities. The analyses indicated that on this soil, use of the surge flow system did not lead to increased spatial uniformities of soil water contents compared with the continuous-flow system. Use of the subsurface drip system resulted in very non-uniform soil water contents above the depth of the emitters. Variability in water contents below the emitter depth was comparable to the surface irrigation systems. Received: 26 March 1996     

Pressure chamber procedures for leaf water potential measurements of cotton

Summary Measurement of leaf water potential ( _l ) with a pressure chamber is usually regarded as a reliable and practical field technique. However, recent evidence indicates that results depend on the measurement techniques employed. Field experiments were conducted to identify the magnitude and sources of error affecting pressure chamber measurements of _l in cotton (Gossypium hirsutum L.) and to develop an accurate and operationally flexible procedure. Water potential of bare cotton leaves was about 0.2 MPa less than aluminum foil wrapped leaves when the elapsed time between excision to chamber pressurization was less than 30 s. The water potential of intact leaves increased 0.3 MPa after 15 s of enclosure in aluminum foil. 5 to 30 min of enclosure were sufficient to reach equilibrium between _l and water potential within the plant stem. Aluminum foil wrapped leaves maintained their _l for 2 h stored in a humid, dark box at 21–28 °C while wet wrapped (cheesecloth) or bare leaf _l increased after one hour because of hydration. An accurate and operationally flexible _l measurement procedure, suitable for large scale sampling, was defined.Contribution from the USDA-ARS, Water Management Research Laboratory, 2021 S. Peach, Fresno, CA 93727 and the Dept. of Land, Air and Water Resources, University of California, Davis, CA 95616, USA     

The effects of applied water at various fractions of measured evapotranspiration on reproductive growth and water productivity of Thompson Seedless grapevines

The reproductive growth and water productivity (WP_b) of Thompson Seedless grapevines were measured as a function of applied water amounts at various fractions of measured grapevine ET_c for a total of eight irrigation treatments. Shoots were harvested numerous times during the growing season to calculate water productivity. Berry weight was maximized at the 0.6–0.8 applied water treatments across years. As applied water amounts increased soluble solids decreased. Berry weight measured at veraison and harvest was a linear function of the mean midday leaf water potential measured between anthesis and veraison and anthesis and harvest, respectively. As applied water amounts increased up to the 0.6–0.8 irrigation treatments there was a significant linear increase in yield. Yields at greater applied water amounts either leveled off or decreased. The reduction in yield on either side of the yearly maximum was due to fewer numbers of clusters per vine. Maximum yield occurred at an ET_c ranging from 550 to 700 mm. Yield per unit applied water and WP_b increased as applied water decreased. The results from this study demonstrated that Thompson Seedless grapevines can be deficit irrigated, increasing water use efficiency while maximizing yields.     

Water use of young Thompson Seedless grapevines in California

Water use of Thompson Seedless grapevines during the first 3 years of vineyard establishment was measured with a large weighing lysimeter near Fresno, California. Two grapevines were planted in a 2ǸǶ m deep lysimeter in 1987. The row and vine spacings in the 1.4-ha vineyard surrounding the lysimeter were approximately 3.51 and 2.15 m, respectively. Vines in the lysimeter were furrow-irrigated from planting until the first week of September in 1987. They were subsequently irrigated with subsurface drip-irrigation whenever they had used 2 mm of water, based upon the area of the lysimeter (equivalent to 8 liters per vine). The trellis system, installed the second year, consisted of a 2.13 m long stake, driven 0.45 m into the soil with a 0.6 m cross-arm placed at the top of the stake. Crop coefficients (K_c) were calculated using measured water losses from the lysimeter (ET_c) and reference crop evapotranspiration (ET_o) obtained from a CIMIS weather station located 2 km from the vineyard. Water use of the vines in 1987 from planting until September was approximately 300 mm, based on the area allotted per vine in the vineyard surrounding the lysimeter. Daily water use just subsequent to a furrow-irrigation event exceeded ET_o (>6.8 mm day^у). Water use from budbreak until the end of October in 1988 and 1989 was 406 and 584 mm, respectively. The initiation of subsurface drip-irrigation on 23 May 1988 and 29 April 1989 doubled ET_c measured prior to those dates. Estimates of a 'basal' K_c increased from 0.1 to 0.4 in 1987. The seasonal K_c in 1988 increased throughout the season and reached its peak (0.73) in October. The highest K_c value in 1989 occurred in July. It is suggested that the seasonal and year-to-year variation in the K_c was a result of the growth habit of the vines due to training during vineyard establishment. The results provide estimates of ET_c and K_c for use in scheduling irrigations during vineyard establishment in the San Joaquin Valley of California and elsewhere with similar environmental conditions.