Effect of soil depth and erosion on yield in the Mississippi Blacklands
1988
Hairston, J.E. | Sanford, Jo | Rhoton, F.E. | Miller, J.G.
Farmer fields were used 4 consecutive yr (1982-1985) to determine effects of soil depth and other parameters on soybean [Glycine max. (L.) Merr.] yield in the Mississippi Blackland Prairie. Soybean yields were sampled on 25 miniplots (1.8 m2) at each of two sites the first 2 yr and from six sites the third and fourth years. Soil depth ranged from 100 to 1500 mm across the miniplots at each site, and most plots had a silty clay texture. Soil samples were collected the second, third and fourth years from the 0- to 150-mm depth and analyzed for pH, organic matter and extractable nutrients. Seasonal rainfall distribution was measured at each site the third and fourth years. Grain yields were variable from year to year for specific sites as well as from site to site within a given year. Regression analyses indicated that differences from site to site were due to variation in soil organic matter and rainfall distribution; whereas, differences within a site were influenced by organic matter, soil depth, and other parameters such as pH and available K which were related to depth. Grain yields ranged from near zero to over 2.5 Mg ha-1, depending on depth, organic matter content and seasonal rainfall distribution. Differences due to fertility were less pronounced. Soil depth was a much better predictor of yield at sites with low organic matter, especially when rainfall was also low. A regression model for depth vs. yield indicated that 10 mm of soil was worth an average of 0.006 Mg ha-1 of soybean grain within the 500- to 1500-mm depth but worth 0.06 Mg ha-1 within the 50- to 150-mm depth.
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