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S.M. Olson

Three in-row spacings of 46, 61, and 76 cm were combined with three pruning methods [none, light (half the suckers removed from the ground to the fork), and heavy (all suckers removed from the ground to the fork] in a complete factorial design. Three harvests were made and responses differed among harvests. At first harvest yields decreased as in-row spacing increased and yields increased as degree of pruning increased. No interactions occurred. At second harvest yields again decreased as in-row spacing increased but only heavy pruning decreased yields. A interaction occurred where the closest in-row spacing pruned lightly did not follow the same pattern as the other two row spacings pruned the same. At third harvest yields increased as in-row spacing increased but pruning method had little effect. With seasonal total yield, in-row spacing had little effect but heavy pruning reduced seasonal total yield over none or light pruning.

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S. M. Olson and Salvadore J. Locascio

Four experiments were conducted to evaluate the influence of transplant age and container size on `Green Duke' broccoli production. Transplant ages (weeks from seeding) were 3, 4, and 5 weeks in Exp. A, 4, 5, and 6 weeks in Exps. B and D and 3, 4, 5, and 6 weeks in Exp. C. Cell sizes were 2.0 cm (width) × 3.2 cm deep (2.0 cm), 2.5 cm × 7.2 cm deep (2.5 cm), and 3.8 cm × 6.4 cm deep (3.8 cm) with each transplant age. With the smallest container size (2.0 cm), yields were significantly lower in 3 of 4 experiments as compared to the 3.8 cm container size. In 2 of 4 experiments, yields were lower with the 2 cm size as compared to the 2.8 cm container size. In Exps. A and B transplant age did not influence yield, but use of the oldest transplants in Exp. C resulted in reduced yields while use of the oldest transplants in Exp. D resulted in the highest yields Generally, head weights followed similar patterns to the yields.

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S.M. Southwick, W. Olson and J. Yeager

Soil applied potassium (K) may not alleviate K deficiency in fine textured California soils when high numbers of prunes per tree are produced leading to leaf necrosis and limb death. Because K demand is increased by fruit, K nitrate (KN) sprays appear to be a corrective option for growers in this situation. Our objectives were to determine best seasonal KN spray liming strategies to minimize K deficiency, quantify K uptake into leaves after spray and to evaluate spray effects on productivity. Results indicated that regardless of spray timing leaf K was increased by approximately 0.3% and three weeks later decreased 0.2%. Average leaf K in sprayed trees was 0.7% higher than untreated trees at harvest. Fruit fresh to dry weight ratios were lower (better) from summer sprayed trees than spring. Summer KN sprayed trees had yield efficiencies equal to those having soil applied K. Fruit size was similar regardless of K application method. Foliar KN sprays may be a viable K augmentation to soil application in heavy crop years on fine textured soils.

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S. J. Locascio, S. M. Olson and D. D. Gull

Tomatoes (Lycopersicon esculentum Mill.) were grown on a sand and loamy sand to evaluate the effects of K source, K rate, and Ca rate on plant nutrient uptake, fruit yield, and fruit quality. The K was applied at 200 and 400 kg K·ha-1 from KCl and K2SO4. Gypsum was applied at 0, 450 and 900 kg Ca·ha-1. On the sand, tomato N leaf tissue concentrations were higher with K2SO4 than KCl. Leaf K concentrations were higher and Ca contents were lower with the higher than lower K rate. At first fruit harvest, leaf Ca concentrations were linearly increased with an increase in Ca rate. Early and total fruit yields, however, were not influenced by K source, K rate, or Ca rate at both locations Marketable fruit were more firm with K2SO4 than KCl and with 200 than 400 kg K·ha-1 on the sand. Fruit were less firm on the sandy loam than sandy soil but was not affected by K source or rate on the former soil. Ca rate had no effect on fruit firmness on either soil. Fruit citric acid contents were higher with KCl than K2SO4 and with 400 than 200 kg K·ha-1, Fruit color and percentage dry weight were not affected by treatment.

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G.H. Clough, S.J. Locascio and S.M. Olson

Broccoli (Brassica oleracea L. var. italica), followed by tomato (Lycopersicon esculentum Mill) or squash (Cucurbita pepo L. var. melopepo), and then broccoli were produced in succession re-using the same polyethylene-mulched beds at two locations with different soil types. First-crop broccoli yield was earlier and greater with drip than with overhead irrigation and increased as N-K rate increased from 135-202 to 270-404 kg·ha-1. On a tine sandy soil, yields of second and third crops produced with residual or concurrent fertilization increased with an increase in N-K rate. On a loamy fine sandy soil, yields also increased as the rate of residual N-K increased; yields of second and third crops did not respond to rate of concurrently applied N-K, but were higher with concurrent than with residual fertilization, except total tomato yields were similar with either application time. With drip irrigation and concurrent weekly fertigation, yields equalled or exceeded those obtained with preplant fertilization and overhead irrigation.

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G.H. Clough, S.J. Locascio and S.M. Olson

Squash (Cucurbita pepo L. var. melopepo) was grown at two locations with different soil types as a second crop in a succession cropping study that used previously cropped polyethylene-mulched beds. Squash was produced with drip or overhead irrigation and with concurrent N-K fertilization or residual fertilizer from the previous crop. Tissue mineral concentration responses to irrigation method were variable; in early fruit, N and K concentrations were higher with overhead than for drip, but leaf Ca and Mg concentrations were higher with drip than with overhead irrigation. Concentrations of N and K were higher with concurrent than with residual fertilization and increased with an increase in application rate. In contrast, concentrations of P, Ca, and Mg decreased with concurrent fertilization and an increase in application rate.

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S.M. Olson, D.O. Chellemi and P.C. Andersen

Since the fall of 1986, tomato growers in northwestern Florida and southwestern Georgia production areas have encountered plants in their fields with unusual growth characteristics. Early symptoms consist of interveinal chlorosis of the young leaves. Subsequent top growth becomes severely distorted with leaflets along the midrib failing to expand properly, resulting in a “little-leaf” appearance. Additional symptoms included cessation of terminal growth, leaves with twisted and brittle midribs, and axillary buds failing to develop properly. Fruit that set on mildly affected plants are distorted, with radial cracks extending from the calyx to the blossom scar. In severely affected plants, fruit failed to set. The problem usually occurs at very low levels, but in 2 years since 1986, the problem has caused some economic damage. To determine a possible cause, samples were taken for virus detection. None were detected in affected plants. Samples were also taken of tissue and soil from affected areas for nutrient and pesticide analysis. No explanation could be developed from any of the tissue or soil samples. The problem usually occurs in wet areas and after very warm temperatures. The problem appears to be very similar to a nonparasitic disease that occurs in tobacco, called “frenching.” In tobacco, frenching occurs in wet, poorly aerated soils with a soil pH >6.3 and during warm temperatures. There seems to be an organism or organisms present under certain conditions that live on the root surface and exude chemicals that cause this distorted growth.

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S.M. Southwick, W. Olson, J. Yeager and K.G. Weis

During the fruit growing season, April through August 1990, 1991, and 1992, four sprays of 20-22 liters/tree of KNO3 were applied to `French' prune trees (Prunus domestica L. syn. `Petite d'Agen). Spray applications of KNO3 were compared to single annual soil applications of KCl (1.4-2.3 kg/tree) and sprays of urea + KNO3 with respect to leaf K and N, fruit size, drying ratio, and dry yield. Potassium nitrate sprays were as effective, or better, than soil-applied K in maintaining adequate levels of leaf K throughout the season. Treatment effects were not carried over into the next year. Lowest leaf K was found in trees where no K had been applied. Those values were below the adequate level of 1.3% K and the untreated group developed K deficiency symptoms. Consistent effects on leaf K were not obtained when urea was applied and no negative effect on leaf K was demonstrated. Equivalent dry yields per tree were obtained by foliar and soil K applications. There was no best time for KNO3 sprays. Yield per tree was not enhanced when foliar K-N sprays were applied to trees that had levels of 1.3% K or more as of 15 Apr. 1992. Trees that were below optimum K in April tended toward improved dry yields after four K-N sprays. Trees that had no applied K were lowest yielding. Drying ratios and fruit size (number of fruit per kilogram) were not different among K treatments. Dry yields per tree were increased without a decrease in fruit size or an increase in drying ratio with either soil or foliar K application. These results suggest that foliar KNO3 sprays applied four times throughout the growing season can be used to correct incipient K deficiency in `French' prune and to obtain dry yields equivalent to those obtained with soil applications of KCl.

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S.J. Locascio, F.M. Rhoades, S.M. Olson, G.J. Hochmuth and E.A. Hanlon

Tomato (Lycopersicon esculentum Mill.) was grown with drip irrigation on a fine sand and on a fine sandy loam to evaluate the effect of N and K time of application on yield. On the sandy soil, 196–112 kg of N–K/ha was applied with 0%, 40%, or 100% preplant with 100% or 60% applied in six or 12 equal or in 12-week variable applications. Marketable fruit yields were lowest with 100% preplant, intermediate with 100% drip-applied, and highest with 40% preplant with 60% drip-applied. With 100% drip-applied, yields were highest with 12 even than with six even weekly applications or with 12 variable N and K applications. With the 40% preplant, timing of application had little effect on yield. On the sandy loam soil in 1993, where only N was applied (196 kg·ha–1), yields were highest with 100% preplant, intermediate with 40% preplant and 60% drip-applied, and lowest with all N drip-applied. In 1994, when excessive rains occurred, yields were similar with all preplant and with split-N applications.

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G.J. Hochmuth, S.J. Locascio, F.M. Rhoades, S.M. Olson and E.A. Hanlon

Tomato (Lycopersicon esculentum Mill.) was grown on fine sand and fine sandy loam soils at two sites to evaluate effects of N and K fertilization practices on petiole fresh sap N and K concentrations and to determine N and K sufficiency ranges. Treatments included applying N (196 kg·ha–1) and K (112 kg·ha–1) either 0%, 40%, or 100% preplant. With 0% or 40% preplant treatments, the remaining N and K was injected through the drip irrigation system in six or 12 equal weekly amounts or by a variable injection rate with most of the N and K injected between weeks 5 and 10 of the season. Petiole sap K concentration declined during the season, but was not greatly affected by treatment. Petiole N decreased over the season from 1100 to 200 mg NO3-N/liter and decrease was greater for preplant N treatments. Petiole N was correlated with tomato yield, especially for petiole N measured in the period of 5 to 10 weeks after transplanting.