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- Author or Editor: D. A. Smittle x
Abstract
In field experiments, yields of pepper (Capsicum annum L.) were obtained by more frequent irrigation, nitrogen topdressings, and increased plant population. The highest marketable yield resulted when sufficient N was added to maintain soil NO3–N levels between 20 (spring) and 30 (fall) ppm. In both seasons, the number of N topdressings was doubled in order to raise the soil NO3–N maintenance levels from 10 to 20 ppm or from 15 to 30 ppm. Yield increases were influenced by frequent irrigation only when additional N was applied to maintain a higher soil NO3–N. Populations greater than 27,000 plants/ha increased marketable yields in spring and fall by 2.8 and 7.1 MT/ha respectively.
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.
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
Plant and root growth and root distribution of ‘Dixie’ squash (Cucurbita maxima Duch.) were reduced by mechanical soil compaction of a Tifton loamy sand soil. Soil atmospheric O2 and CO2 concentrations were not affected by soil compaction. Marketable fruit yield was reduced 46 to 58% by increased soil strength produced by tractor wheel traffic. Nitrogen from Ca(NO3)2 produced greater yields in non-compacted plots and smaller yields in compacted plots than NH4NO3.
Abstract
Inhibition on phenolase activity by blanching or restriction of exposure to oxygen greatly reduced the rate of internal corrosion of tinplated cans by sweet potatoes independent of variety effect or nitrate concentration of the raw product.
When phenolase activity was not inhibited, the severity of can corrosion varied widely among varieties of sweet potatoes. Varieties which caused more can corrosion had a high phenolase activity and a high nitrate concentration. ‘Nemagold’ and ‘California 20-51D’ sweet potatoes, which have a relatively low phenolase activity, did not accumulate high nitrate concentrations or severely corrode cans when ammonium nitrate fertilization of 1,000 lb./acre was applied. Ammonium nitrate fertilization greatly increased nitrate accumulation and can corrosion by ‘Goldrush’ sweet potatoes.
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
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
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.
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.
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.