Soil Inorganic N Dynamics and Competitive N Uptake Between Rice and Weed in Organic Farming in Entisols, Tsuruoka, Japan

MARGI ASIH MAIMUNAH, Dr. Benito Heru Purwanto, M.P., M.Agr.; Dr. Ir. Sri Nuryani Hidayah Utami, M.P.; Prof. Weiguo Cheng

2021 | Tesis | MAGISTER ILMU TANAH

In organic farming, weeding practice known as an effective way to control weeds and applied for minimizing weeds growth without applying chemical substances to the field. In addition, understanding the critical periods of weed competition were essential to optimize the rice growth. Therefore, this research aims to study on 1) how soil inorganic nitrogen responds to frequencies of weeding, and 2) how weeding practice affects rice and weeds growth. The site of research located in Yamagata University Farm, Yamagata Prefecture, Japan. One kind of popular rice cultivars in Yamagata Prefecture, Sasanishiki was transplanted in late May and harvested in September 2019. Four replications of five weed managements were used in this study, i.e. 0, 2, 4, 6, and 8 times of weeding since transplanting to 49 DAT (days after transplanting) in organic fields. As a reference, we used uncontrolled weed plot, and herbicides weed controlled in conventional fields. Soil, water and plant were sampled periodically to monitored the difference in each period. Major weed encountered in the field were Echinochloa crus-galli, Schoenoplectus juncoides, and Monochoria vaginalis (Burm. f.). The more frequent weeding practice (8WF) would reduce the weeds biomasses compared to those without weeding by 78.69% lower. While rice nitrogen uptake increased 2 to 4 times higher, increment of weeding frequencies negatively affected weed biomass and nitrogen uptake. 8WF enhanced soil NO3- to the highest average among all plots (10.12 mg N kg-1). Meanwhile, 6WF performed highest soil NH4+ among organic plots (10.36 mg N kg-1).

In organic farming, weeding practice known as an effective way to control weeds and applied for minimizing weeds growth without applying chemical substances to the field. In addition, understanding the critical periods of weed competition were essential to optimize the rice growth. Therefore, this research aims to study on 1) how soil inorganic nitrogen responds to frequencies of weeding, and 2) how weeding practice affects rice and weeds growth. The site of research located in Yamagata University Farm, Yamagata Prefecture, Japan. One kind of popular rice cultivars in Yamagata Prefecture, Sasanishiki was transplanted in late May and harvested in September 2019. Four replications of five weed managements were used in this study, i.e. 0, 2, 4, 6, and 8 times of weeding since transplanting to 49 DAT (days after transplanting) in organic fields. As a reference, we used uncontrolled weed plot, and herbicides weed controlled in conventional fields. Soil, water and plant were sampled periodically to monitored the difference in each period. Major weed encountered in the field were Echinochloa crus-galli, Schoenoplectus juncoides, and Monochoria vaginalis (Burm. f.). The more frequent weeding practice (8WF) would reduce the weeds biomasses compared to those without weeding by 78.69% lower. While rice nitrogen uptake increased 2 to 4 times higher, increment of weeding frequencies negatively affected weed biomass and nitrogen uptake. 8WF enhanced soil NO3- to the highest average among all plots (10.12 mg N kg-1). Meanwhile, 6WF performed highest soil NH4+ among organic plots (10.36 mg N kg-1).

Kata Kunci : Soil inorganic nitrogen, weeding frequencies, N uptake, weed-rice competition, organic farming