Behavior of 42 crop species grown in saline soils with high boron concentrations

The coastal region of northern Chile is a desert and the salinity and boron levels in the soils can be high. The irrigation water is also saline (3-9 dS/m), with high concentrations of sodium, chloride, and boron. Despite these conditions, the irrigation of alfalfa, winter grains, and vegetables has been practiced on the alluvial soils near the rivers, since before the arrival of the Spanish in the 16th century. A field experiment was conducted in 1989 and 1990 to document the effects of irrigation on the growth and yield of 42 crop species near the city of Calama. The EC of the Loa river water used in the study was 8.2 dS/m and the boron content was 17 mg/l. This EC level exceeds the threshold salinity of most crops, and the boron level exceeds the threshold level for all crops. The crops were planted in December of 1989 and harvested the following May. Drip irrigation was used. The plant growth and crop yields of artichoke, asparagus, broad bean, red and sugar beets, swiss chard, carrot, celery, a local variety of sweet corn, potato, prickly pear cactus, onion, shallot, spinach, were greater than expected based on published information. If separate effects of salinity and boron were additive, little or no growth would be expected for all 12 of these crops. Interactions likely occur which increase the individual tolerance coefficients for boron and salinity when a crop is exposed to both sources of stress at the same time. Foliar levels of boron may be reduced because high soil salinity levels reduce plant water uptake, The milder climate in Chile compared to that in Riverside, CA, where much of the salt and boron tolerance data has been obtained, could be partially responsible for the better crop response to salinity and boron than expected. Finally, the productivity of the local variety of sweet corn suggests that it is a more salt-tolerant variety, which has arisen as a consequence of seed selection practiced since the time irrigation began in the region which predates the 16th century. (C) 1997 Elsevier Science B.V.