Effect of the Nitrification Inhibitor 3,4-Dimethylpyrazole Phosphate on the Deep Placement of Nitrogen Fertilizers for Soybean Cultivation

Soshi Hatano; Yoichi Fujita; Yoshifumi Nagumo; Norikuni Ohtake; Kuni Sueyoshi; Yoshihiko Takahashi; Takashi Sato; Sayuri Tanabata; Kyoko Higuchi; Akihiro Saito; Takuji Ohyama

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.
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.

Keywords: Nitrification inhibitor, dimethylpyrazole phosphate, nitrogen fertilizers, soybean cultivation

Abstract

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 gm^?2) and DMU (461 gm^?2) and relatively low in CU (405 gm^?2), U (396 gm^?2), and Cont (373 gm^?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.