Effect of soybean residue on the nitrogen uptake by wheat cultivated after soybeans during double cropping on a paddy field
2005
Hara, Y.(National Agricultural Research Center for Kyushu Okinawa Region, Nishigoshi, Kumamoto (Japan)) | Tsuchiya, K. | Kusa, K.
When wheat is grown after soybeans, it is necessary to reduce the amount of nitrogen applied compared to when wheat is cultivated after rice. Although soil analysis is effective for estimating the reduction in nitrogen, it does not reflect the effect of soybean residue left on the field until the field is plowed for wheat, because soil is generally analyzed after the bulky matter has been removed. Therefore, we compared the nitrogen uptake by wheat cultivated in the absence or presence of soybean residue to estimate the effects of the residue. In addition, we investigated the decomposition of soybean residue, the mineralization and organization of nitrogen derived from the residue, and the difference in the amount of nitrogen available in the soil before and after soybean cultivation. We found that the decomposition of soybean residue organized the soil mineral nitrogen in the early stage of wheat cultivation, and the organized nitrogen was remineralized in the later stage of wheat cultivation, which raised the nitrogen content of the wheat. However, soybean residue did not affect the nitrogen uptake by wheat at harvest time. Since there was more available nitrogen and greater nitrogen uptake by wheat in the field in which soybeans had been cultivated, the effect of soybean cultivation on the subsequent wheat cultivation may be small as a result of soybean residue and large as a result of the remaining soil. Accordingly, with double cropping, the basal nitrogen application for wheat cultivation following soybean cultivation could be estimated by analyzing soil from which the soybean residue has been removed. The topdressing nitrogen application may be reduced by an amount that corresponds to the increase in wheat nitrogen uptake caused by soybean residue in the later stage of wheat cultivation.
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