Yield and Nitrogen Yield of Sorghum Intercropped with Nodulating and Nonnodulating Soybeans

Elmore, R. W.; Jackobs, J. A.

Yield and Nitrogen Yield of Sorghum Intercropped with Nodulating and Nonnodulating Soybeans

1986

Elmore, R. W. | Jackobs, J. A.

Nitrogen transfer between intercropped legumes and nonlegumes has not been consistently documented. However, N transfer between mixtures of nodulating (Rj₁) and nonnodulating (rj₁) soybeans (Glycine max (L.) Merr.) has been shown. A 2-yr field study was conducted to examine the effects of intercropped nodulating and nonnodulating soybeans on sorghum [Sorghum bicolor (L.) Moench] yield and N yield, and N transfer. In both years, the soybean cultivar (cv.) Clark 63 (Rj₁) and its rj₁ isoline, L73-1054, were planted at different distances between sorghum (‘DeKalb BR45+’) rows. Nitrogen rate was either 0 to 100 kg N/ha in 1979 and either 0 or 175 kg N/ha in 1980. The soil was a Cisne silt loam (mesic Mollic Albaqw in both years. Monocultures of both crops were also planted in both years. Sorghum N yield was 9% greater with Rj₁ than with rj₁ in 1979. This was due to increased N yield of sorghum associated with Rj₁ in 0.4 m rows; soybean cv. had no effect on sorghum N yield in 0.8 m rows. Sorghum yield was not affected by soybean CV. Yields and competition of rj₁ soybeans in 1980 were severely reduced by the hotdry growing season confounding N-accumulation differences between rj₁ and Rj₁. However, from the 1979 results, we conclude that sorghum N accumulation was increased by association with Rj₁ soybeans through N transfer, and that closer proximity of sorghum and soybeans enhanced this beneficial effect.

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