The deep placement of urea fertilizer (DMU) containing 1% (W/W) of the nitrification inhibitor 3,4- dimethylpyrazole phosphate (DMPP) on soybean growth and seed yield was as effective as those of the coated urea (CU) and lime nitrogen (LN) in a field research. The average seed yields were high in LN (464 g•m−2) and DMU (461 g•m−2) and relatively low in CU (405 g•m−2), U (396 g•m−2), and Cont (373 g•m−2) treatments. The accumulations of dry matter and nitrogen in soybean shoots were higher in the plants with deep placement of CU, LN and DMU than U and Cont. The daily nitrogen fixation activity and daily nitrogen absorption rate were calculated based on the relative ureide method. Both nitrogen fixation activity and nitrogen absorption rate were higher in DMU, CU, and LN compared with control treatment, suggesting that the deep placement of DMU did not repress nitrogen fixation. Soil incubation test was performed using the same field soil with DMU, U, LN, and urea with DMPP 1%, 2%, and 4%. DMU inhibits nitrification similar to the pattern of LN until 8 weeks. The increasing DMPP concentration did not markedly increase the nitrification inhibition. From these results, it was concluded that urea fertilizer with 1% DMPP is efficient for deep placement of N fertilizer for soybean cultivation due to its lower price compared with CU and LN.
Author(s) Details
Takuji Ohyama
Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan and Faculty of Applied Biosciences, Tokyo University of Agriculture, Tokyo 156-8502, Japan.
Soshi Hatano
Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan.
Yoichi Fujita
Niigata Agricultural Research Institute, Crop Research Center, Niigata 940-0826, Japan.
Yoshifumi Nagumo
Niigata Agricultural Research Institute, Crop Research Center, Niigata 940-0826, Japan.
Norikuni Ohtake
Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan.
Kuni Sueyoshi
Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan.
Yoshihiko Takahashi
Graduate School of Science and Technology, Niigata University, Niigata 950-2181, Japan.
Takashi Sato
Faculty of Bioresource Sciences, Akita Prefectural University, Akita 015-0055, Japan.
Sayuri Tanabata
College of Agriculture, Ibaraki University, Ibaraki 300-0332, Japan.
Kyoko Higuchi
Faculty of Applied Biosciences, Tokyo University of Agriculture, Tokyo 156-8502, Japan.
Akihiro Saito
Faculty of Applied Biosciences, Tokyo University of Agriculture, Tokyo 156-8502, Japan.
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