ISHS Acta Horticulturae 594: International Symposium on Foliar Nutrition of Perennial Fruit Plants
PROPERTIES AND PERFORMANCE OF BORON SPRAY PRODUCTS FOR APPLE |
| Author: | F.J. Perya |
| Keywords: | apple, Malus x domestica Borkh., micronutrient, nitrogen, sodium |
| Abstract:
Boron deficiency is a widespread and chronic problem in tree fruit-producing regions of the world. Washington State University guidelines encourage growers to apply annual maintenance sprays of B to offset the natural tendency for tree B status to decline over a period of years. Early bloom spray timing often is used to ensure that sufficient amounts of B are available for pollen tube growth, flower fertilization, fruit set, and early fruitlet development. A five-year field study was initiated in 1996 to compare the effectiveness of new foliar B fertilizers relative to the standard product Solubor. The test trees were Fuji/EMLA.26 apple grown on sandy loam soil in an irrigated orchard located in semi-arid central Washington State, USA. The sprays were applied by hand-gun at the pink flowering stage. Treatments were water control, Mor-Bor 17, Solubor, Solubor DF, Spraybor, Borosol, Liquibor, N-Boron, Solubor plus Coron, and Solubor applied only to the ground. Application rates were modified during the course of the experiment: 0.56 kg B ha-1 in 1996-98; 1.12 kg B ha-1 in 1999; and no sprays in 2000. All of the B sprays increased flower cluster B in all years. The B sprays usually but not always increased leaf B. Increasing the B rate substantially increased plant tissue B. In general, there was little substantive difference between the eight products/product mixtures, suggesting that B availability from the sprays was the same regardless of the form of B occurring in the marketed product (borate vs. polyborate). Flower cluster B in the ground-applied Solubor treatment was similar to the water control; however, leaf B corresponded to the other B products, indicating effective uptake of B from the soil during the early summer. The presence of urea or polymeric urea compounds did not improve plant tissue B status. Flower cluster Na but not leaf Na was positively related to the amount of Na in the B products. Fruit quality was not affected by the B spray treatments in any year. Flower cluster and leaf B concentrations returned to near or at control levels in the season following the last spray application, suggesting limited accumulation and/or remobilization of intra-tree B reserves. This last observation validates the recommendation for annual B fertilizer applications to maintain adequate tree B status under Washington conditions. | |
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