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Alfalfa Growth and Soil Oxygen Diffusion as Influenced by Depth to Water Table¹

ABSTRACT

Growth and yield of alfalfa and oxygen diffusion rate (ODR) as influenced by excess water were investigated via three depth to water table (WT) treatments, through two different falling water table sequences. The environment for the study was a simulated profile of a Munson silty clay loam, mesic frigid Aeric Haplaquepts, placed in 12 large cylinders 0.61-m diam by 1.52 m deep each seeded to Iroquois alfalfa (Medicago sativa L.). Each sequence was run through three consecutive 42-d growth cycles. The first sequence was one flooding-recession per growth cycle while the second sequence included three floodings at two-week intervals during each cycle. Each cycle began immediately after previous crop harvest, with 3-d saturation followed by lowering the WT to fixed 0.15-, 0.45-, and 0.75- m depths, respectively. ODR values at a 0.075-m depth averaged over three growth cycles from the single falling water table treatment showed little change during the saturation to drawdown period for the 0.15-m WT but highly significant variation for the 0.45- and 0.75-m WT treatments. Growth rates for all treatments followed a pattern of two weeks of rapid growth followed by a declining growth rate to harvest. For the sequence having three flooding-drawdowns per cycle, crop growth and yield increased significantly as a linear function of WT depth from 0.15 to 0.75 m. The soil water system showed a 3- to 4-d drawdown after each flooding with WT drawdown having a positive effect to a 0.75-m depth.

¹ Contribution from USDA, ARS and Maine Agric. Exp. Stn., Orono, Cooperating.

² Agricultural Engineer, and Soil Scientist, USDA-ARS, New England Plant, Soil and Water Lab. (NEPSWL), Univ. of Maine, Orono, ME 04469; and Engineering Assoc., Assoc. Prof. of Horticulture and Assoc. Prof. of Agricultural Engineering, Univ. of Maine, Orono 04469, respectively. The second author is now at North Central Soil Conservation Research Lab., Morris, MN 56267.

Received for publication November 28, 1983. Accepted for publication April 23, 1984.