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- Author or Editor: D. A. Smittle x
Abstract
Response of sweet corn (Zea mays L.) to tillage methods on a Tifton loamy sand was investigated during 1976 and 1977. The greatest volume of soil having a strength of less than 100 N/cm2 core index resulted from moldboard plowing to a depth of 28-30 cm. The smallest volume of low-strength soil resulted from disk harrowing to a depth of 10-13 cm. Soil strength patterns produced by these tillage methods were relatively uniform across the seedbed. A subsoil-bed system produced a channel of low-strength soil under the row to a depth of 40 cm; however, soil strengths 15 cm to the side of the row were similar to the disk harrow method. Soil strength patterns resulting from subsoil-plant systems were similar to subsoil-bed. Soil strength increased during the growing seasons with tillage differences evident near harvest. Root growth, plant growth, yield, and nutrient uptake efficiency responses of sweet corn were proportional to the volumes of low-strength soil at planting.
Abstract
The disk, deep turn and rip-bed methods of land preparation resulted in soil strengths of 1000 kPa or greater at depths of 10, 28 and 18 cm, respectively. The disk and deep turn treatments produced a relatively uniform soil strength across the seed bed at all depths while the rip-bed treatment resulted in a channel of low strength soil under the row with relatively high soil strengths 15 cm to each side. Root growth generally followed the same pattern as soil strength. Shelled pea yield was greatest with the deep turn tillage method and lowest with the disk tillage method. The greater yield was due to a combination of a larger yield per plant and a slightly greater plant stand with the deep turn tillage method. Nutrient use efficiency as determined by total nutrient uptake by plants of the rip-bed and deep turn treatments was 40 and 50% greater than those from the disk treatment.
Abstract
Pepper (Capsicum frutescens L. cv. Hot Hungarian Yellow Wax) and polebeans (Phaseolus vulgaris L. cv. Dade) were grown in an intensive production system with film mulch, broad-spectrum soil fumigation and trickle irrigation. Nitrogen was applied through the trickle irrigation tubes at 0.56, 1.12, 2.24, and 4.48 kg/ha per day for the pepper and 0.56, 1.12, 2.24, and 3.36 kg/ha per day (doubled 6 weeks after seeding) for polebeans. Potassium was applied at 0.83 times the N rate. The N and K were applied twice weekly for the polebean and with every irrigation for the pepper. Marketable pepper yields ranged from 59.6 MT/ha with the low fertilizer rate to 96.0 MT/ha with high fertility. Yield increases with increasing fertilizer rates were not as great with polebeans as with peppers but there was a trend for higher yields with increasing fertilizer rates.
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
Seed of snap bean, Phaseolus vulgaris L. cv. Avalanche were separated into 3 length or 3 diameter groups and then each group separated into 3 classes based on aerodynamic properties. The grading procedure resulted in seed grades having large differences in physical characteristics, growth and yield responses. Yield response potential of snap bean was determined primarily by seed weight. A grading method utilizing size grading based on seed diameter followed by aspiration in a vertical air column was the most effective method of eliminating seed with low yield potential.
Abstract
Root growth of cucumber (Cucumis sativus L.) was not greatly restricted by soil strength less than 500 kPa (5 bars). Root growth was inhibited 80% at a soil strength of 850 kPa. Mechanical compaction produced by a tractor wheel resulted in a 50% reduction of tissue NO3 at comparable soil NO3 levels, a 25 to 35% yield reduction, and a decrease in fruit length/diameter ratio. The effects of soil compaction could be partially alleviated by increasing the rate of nitrogen fertilization; however, a 3-fold increase in N fertilization did not completely counteract the effect of compaction on cucumber yield. A system for cucumber seedbed preparation which reduces soil compaction is presented.
Abstract
Removal of 20% of the seed of a commercial ‘Poinsett’ seed lot in a vertical air column increased the mean thickness and weight of the remaining seed. Fruit yield was increased by use of thicker, heavier seed when yield potential was not limited by high soil strengths. Seed grading effect on cucumber yield was less when either soil compaction or climactic conditions reduced yield potential. A combination of both yield limiting factors eliminated seed grading effect. Yield response to source of nitrogen was different when cucumbers were grown on compacted and noncompacted seedbeds. An interaction of seed grade, nitrogen source and seedbed compaction on marketable fruit yield was found.
Nitrogen applied as NH4-N or NO3-N (75 mg·liter-1) affected onion (AIlium cepa L.) plant growth when grown in solution culture. Nitrate alone or in combination with NH4-N increased leaf fresh and dry weight, leaf area, root fresh and dry weight, and bulb dry weight when compared to growth with NH4-N as the sole N source. Bulb fresh weight was highest with an NH4-N: NO3-N ratio between 1:3 and 3:1. Maximum leaf fresh weight was not necessary to produce maximum bulb fresh weight when onions were subjected to different N-form ratios. Precocious bulbing resulted when NH4-N was the sole N source; however, high bulbing ratios early in plant development were not correlated with final bulb fresh weight. Nitrogen form also influenced water uptake and pungency, as measured by enzymatically developed pyruvate concentration, but did not affect bulb sugar concentration.
Yields of `Granex 33' and `Behairy' onions (Allium cepa) closely correlated with the weight of the seeds used to establish the stand. Elemental content was consistently higher in heavier seeds, but elemental concentrations in the seeds were generally negatively related to seed weight, onion growth, and yield. A combined size-aspiration grading was an effective means of eliminating seed with low-yield potential.