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Abstract
Summer squash (Cucurbita pepo L. cv. Dixie hybrid) were grown in drainage lysimeters under closely controlled and monitored soil water regimes. Variables included three irrigation treatments, three growing seasons, and two soil types. Marketable fruit yield was greatest and production cost per kilogram of marketable fruit was least when squash was irrigated at 25 kPa of soil water tension. Yields were greatest for the spring season of production and least for the fall season. Regression equations are provided to describe the relationships of water use to plant age and to compute daily evapotranspiration : pan evaporation ratios (crop factors) for squash irrigated at 25, 50, and 75 kPa of soil water tension during the spring, summer, or fall production season.
Abstract
Two snap bean cultivars, ‘Galagreen’ and ‘Eagle’, were grown in rainfall sheltered irrigation plots as spring and fall crops. Pod yield of snap beans irrigated when the soil water tension reached 25 kPa (0.25 bar) averaged 11.9 MT/ha. Application of irrigation at soil water tensions of 50 kPa (0.5 bar) and 75 kPa (.75 bar) reduced yield by 41% and 48%, respectively. The reduction in water use was proportionately less than yield decreases, resulting in water use efficiencies of 0.62, 0.45 and 0.40 MT of pods/cm of water for the 25, 50 and 75 kPa irrigation treatments. Water use by the cultivars was similar, but pod yield and water use efficiency of ‘Eagle’ was greater than ‘Galagreen’. Pod yields were reduced when plants were subjected to a 75 kPa soil water stress during pre-blossom, blossom or pod development growth stages. The relationships of snap bean water use (ET) to evaporation from an open pan (PA) were established throughout growth. The crop factor value (ET/PA) varied with plant age and irrigation regime.
Abstract
Seed of 11 cultivars of snap bean, Phaseolus vulgaris L., were separated by aerodynamic properties in a vertical air column. Seed physical characteristics associated with air column separation were weight, density, volume, diameter, and length. The separation technique did not affect seed germination, seedling emergence, or plant survival at full expansion of the first trifoliate leaf growth stage. However, seed remaining in the air column after aspiration produced fewer weak plants and fewer plants with root rot at the first trifoliate leaf. These seed produced a greater plant stand, a greater pod weight per plant, a more uniform pod size distribution, and a greater yield at harvest than the seed removed. Yield from seed remaining after air column aspiration was 21% greater than from non-graded seed.
`Rio Verde' cabbages (Brassica oleracea L.) were grown in drainage lysimeters on two soil types (Tifton loamy sand and Bonifay sand) in the spring and the fall of 1982, 1983, and 1985. Irrigation regimes consisted of applying water amounts equal to soil water deficit when the soil water tension at a 10-cm depth exceeded 25, 50, or 75 kPa throughout growth of the crops. Because the lysimeters were equipped with rainfall-activated shelters, water applications and evapotranspiration (ETc) were similar. Crop factors (CF) as functions of plant age (i) were computed for all combinations soil type-season-irrigation regime as the ratio between water applications and class A pan evaporation (Ep). No significant differences were observed among soil type or season, but irrigation regimes significantly affected ETc and CF(i). The highest ETc and leaf yields corresponded to the 25-kPa regime. CF(i)=0.025i - 0.0002li2, 0.023i - 0.00017i2, and 0.022i - 0.00017i2, for the 25-kPa, 50-kPa, and 75-kPa treatments, respectively (R2=0.97). Therefore, daily ETc by cabbages can be computed with Ep as ETc = CF(i) × Ep for scheduling irrigation.