Alfalfa Management Under Saline Conditions with Zero Leaching
1981
Francois, L. E.
Previous studies have shown that alfalfa (Medicago sativa L.) can tolerale high salinity levels in the lower portion of the root zone without significant yield reduction, provided the upper portion of the root zone is maintained relatively free of salinity. The question of how much salt can be stored in the lower root zone before encroachment into the upper root zone occurs with subsequent yield reduction remains unanswered. Consequently, a study was conducted in greenhouse lysimeters to determine salt storage capacity in the lower part of the rootzone and the long-term effects of this management on plant growth. The lysimeter soil was Pachappa fine sandy loam (mixed, thermic, Mollic Haploxeralf). Alfalfa was grown with and without leaching using an irrigation water having an electrical conductivity of 1.0 dS/m in soil profiles 0.6, 1.2, and 1.8-m deep for 9, 14, and 20 months, respectively. During these respective time periods yield from the nonleached lysimeters was reduced less than 25% while more than 14.6,30.2, and 45.6 Mg/ha of salt was stored in the bottom half of the three soil profiles. The deeper the soil the greater the capacity to store salt with minimal yield reduction. Yield was drastically reduced once salt build-up began in the upper portion of the root zone. Consequently, irrigating to leach accumulated salt out of the upper root zone may be necessary but this can be accomplished during the winter or off season when water is more readily available. Shallower soil profiles may require more frequent leaching.
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