This 7-page fact sheet is chapter 2 of the 2018 Vegetable Production Handbook. Written by Guodong Liu, Eric H. Simonne, Kelly T. Morgan, George J. Hochmuth, Monica Ozores-Hampton, Shinsuke Agehara, ...and Rao Mylavarapu, and published by the Horticultural Sciences Department, 2018.
CV296/CV296: Chapter 2. Fertilizer Management for Vegetable Production in Florida (ufl.edu)
This 7-page fact sheet is chapter 2 of the 2018 Vegetable Production Handbook. Written by Guodong Liu, Eric H. Simonne, Kelly T. Morgan, George J. Hochmuth, Monica Ozores-Hampton, Shinsuke Agehara, ...and Rao Mylavarapu, and published by the Horticultural Sciences Department, 2018. CV296/CV296: Chapter 2. Fertilizer Management for Vegetable Production in Florida (ufl.edu)
The goal of this study is to develop a management tool for producing high quality, more stress tolerant vegetable transplants and for prolonging transplant marketability. This study primarily ...involves physiological and morphological growth modulation by the stress hormone abscisic acid (ABA). The first part of this study evaluated the effects of ABA foliar spray on stress and quality management of vegetable transplants. In muskmelon seedlings subjected to water withholding, pre-stress treatment of ABA improved the maintenance of leaf relative water content by limiting transpirational water loss. Upon re-watering, the ABA-treated seedlings showed faster photosynthetic recovery and greater dry matter accumulation than the untreated seedlings. In jalapeño pepper, ABA applied at the cotyledon to 3-leaf stage improved transplant compactness with minimal negative side effects. Although this method induced undesirable growth modifications in bell pepper and watermelon, ABA applied immediately before the transplant maturity stage was effective in delaying excessive shoot growth of bell pepper seedlings. These results demonstrate three beneficial effects of ABA for vegetable transplants: stress control, height control, and extension of transplant marketability. The second part of this study examined the mechanisms of ABA-induced growth modulations in Arabidopsis: inhibition of leaf expansion, leaf chlorosis, and promotion of primary root elongation. Microscopic analysis of leaf epidermis revealed that ABA inhibits cell expansion, but not cell division or stomata formation, suggesting that the ABA-induced inhibition of leaf expansion is a mechanism to conserve water without limiting plant growth capacity. Leaf chlorosis induced by exogenous ABA occurred only in mature leaves and independently of ethylene synthesis. Tissue nitrogen (N) analysis with a (15)N-labelingtechnique indicated a role of ABA as a regulator of N distribution. A proposed new mechanism is that ABA limits distribution of N into non-growing mature leaves, thereby inducing leaf-age dependent chlorosis. Using scanning electron microscopy (SEM), dehydration-induced root damage was characterized by thickening and deformation of root tips. Although exogenous ABA did not alleviate this damage, it promoted primary elongation especially under water stress. These results suggest that the overall function of ABA in stress adaptation is to conserve water and nutrients to support new growth.
Soil incubation and growth chamber studies were conducted to evaluate the effects of soil moisture (50, 70, and 90% of water holding capacity) and temperature (15/10, 20/15, and 25/20°C day/night) on ...nitrogen (N) availability from four organic N sources. In the soil incubation study, differential N release kinetics of the N sources was determined by measuring ammonium- and nitrate-N contents periodically over 12 weeks. Net N released, as a percentage of organic N, was greatest in the order: urea (91–96%) > blood meal (BM) (56–61%) > alfalfa pellets (AP) (41–52%) > partially composted chicken manure (CM) (37–45%). Increasing soil moisture increased net N released from AP and CM by 12 and 21%, respectively, but did not affect net N released from urea and BM. Increasing temperature increased net N released from AP, BM, and CM by 25, 10, and 13%, respectively, but did not affect net N released from urea. In the growth chamber study, kale (Brassica oleracea L.) was grown as an indicator of N availability. Regardless of soil moisture and temperature, N use efficiency by kale was greatest in the order: urea > BM > AP > CM. Soil moisture influenced N availability differently in the two studies, whereas temperature influenced N availability similarly in the two studies. Our results indicate that soil incubation data will be useful for evaluating variations in N availability among N sources and temperatures on a field scale. Increasing temperature improves N availability from natural organic materials, thereby contributing to better crop production.
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