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Title: DOES SALINITY REDUCE BORON'S TOXIC EFFECT IN BROCCOLI?

Author
item Grieve, Catherine
item GRATTAN, STEPHEN - DEP LAWR, UC DAVIS, CA
item Poss, James
item SMITH, T - DEP LAWR, UC DAVIS, CA
item Suarez, Donald

Submitted to: Proceedings of the International Salinity Forum
Publication Type: Proceedings
Publication Acceptance Date: 4/11/2005
Publication Date: 4/25/2005
Citation: Grieve, C.M., Grattan, S.R., Poss, J.A., Smith, T.E., Suarez, D.L. 2005. Does salinity reduce boron's toxic effect in broccoli? In: Proceedings of the International Salinity Forum, Managing Saline Soils and Water: Science, Technology, and Soil Issues. April 25-27, 2005. Riverside, CA pp:67-70.

Interpretive Summary: Reuse of saline drainage water is a management option on the west side of the San Joaquin Valley (SJV) of California that is necessary for reducing the volumes of saline drainage that require disposal. A potential limitation to the use of these waters for agricultural production is the extent by which boron, a naturally-occurring trace element, affects the selection, growth and yield of crops in the reuse system. Boron is a concern for several reasons. First, boron is a microelement that is essential for crops, but has a small concentration window between deficiency and toxicity. Second, it has a higher affinity to soil than most common salts and requires much more water to reduce soil B than it does to reduce the salinity. Furthermore, the B concentration in SJV drainage water varies widely, but in nearly all cases, far exceeds levels that would result in toxic conditions based on B-tolerance guidelines. A greenhouse experiment was conducted at the USDA-ARS George E. Brown Jr. Salinity Laboratory, Riverside, CA. The test crop, broccoli, cultivar "Seminis PX511018" was irrigated with saline waters. Plants were harvested several times during the growing period to determine biomass production and to sample for mineral ion concentration in various plant tissues. Preliminary information indicate that broccoli is more tolerant to boron stress in the presence of salinity than under non-saline conditions.

Technical Abstract: Reuse of saline drainage water is a management option on the west side of the San Joaquin Valley (SJV) of California that is necessary for reducing the volumes of saline drainage that require disposal. A potential limitation to the use of these waters for agricultural production is the extent by which boron, a naturally-occurring trace element, affects the selection, growth and yield of crops in the reuse system. Boron is a concern for several reasons. First, boron is a microelement that is essential for crops, but has a small concentration window between deficiency and toxicity. Second, it has a higher affinity to soil than most common salts and requires much more water to reduce soil B than it does to reduce the salinity. Furthermore, the B concentration in SJV drainage water varies widely, but in nearly all cases, far exceeds levels that would result in toxic conditions based on B-tolerance guidelines. The question is often raised - Are the effects of salinity and boron on crops additive, synergistic or antagonistic. To answer this question, a greenhouse experiment was conducted at the ARS-USDA Salinity Laboratory. Broccoli variety 'Seminis PX511018', was grown in greenhouse sand culture. Irrigation treatments consisted of three salinity levels (electrical conductivities = 2, 11, 18 dS/m); three boron concentrations (0.23, 12, 30 mg/L); two water compositions (1) chloride-dominated salts and (2) waters with ion composition typical of those found in the western SJV; and three replications. Plants were harvested periodically throughout the growing season and again at maturity for biomass and tissue-ion accumulation. Shoots were separated into young and old leaves, stems and heads. Broccoli shoots (leaf and stem tissue) appear to be less sensitive to salinity and boron than the reproductive tissues (head). Marginal chlorosis and leaf cupping occurred when the plants were subjected to the low-salinity and high-boron treatment. Results of this preliminary study indicate that the dual stresses (salt and boron stress) are antagonistic.