Date of Graduation

12-2018

Document Type

Thesis

Degree Name

Master of Science in Crop, Soil & Environmental Sciences (MS)

Degree Level

Graduate

Department

Crop, Soil & Environmental Sciences

Advisor/Mentor

Trenton L. Roberts

Committee Member

Richard J. Norman

Second Committee Member

Larry C. Purcell

Third Committee Member

Edward E. Gbur

Keywords

Agronomy, Crop Rotation, Nitrogen, Rice, Soil Fertility, Soybean

Abstract

Little is known about the effects of soybean (Glycine max L.) management techniques on soil-nitrogen (N) credit development and its impact on the subsequent rice (Oryza sativa L.) crop’s success. This study was conducted to determine how soybean maturity group (MG) and planting date effect overall soybean productivity and its influence on the following rice crop. Various soybean planting dates (optimum and late) and MGs (3.5, 4.7, 5.4, and 5.6) were grown and followed in rotation with a rice crop. Six rates of pre-flood fertilizer-N (0, 44, 89, 134, 179, 224 kg N ha-1) were applied to the rice crop. Soybean grain yield was significantly different amongst MGs in both 2016 (P = 0.0012) and 2017 (P = 0.0004), with the 4.7 relative MG consistently yielding the highest. Soybean total N uptake (TNU) increased with increasing grain yield (P = 0.0167) when all site years were analyzed together. The net N returned to the soil through biomass residue was not significantly influenced by planting date (P = 0.7796) or MG (P = 0.3475).The rice grown in clay soil produced a higher grain yield when following a 5.4 MG soybean (P < 0.0001). On a silt loam soil the interaction of both planting date and MG of the previous soybean crop influenced the maximal grain yield achieved of the rice crop (P < 0.0001) and the N rate needed to achieve 95% relative grain yield (P = 0.0007). At an optimum planting date, soybean MG had little effect on the rice crop but should be selected to achieve the highest soybean grain yield. However, when the soybean crop is planted late, a determinate cultivar should be selected to achieve the highest rice crop TNU, maximal grain yield, and require the lowest rate of fertilizer-N to achieve 95% relative grain yield. Soybean crop management decisions can be highly influential when producing a soybean-rice rotation in Arkansas to maximize overall crop rotation productivity and profitability.

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