Effect of deep placement of controlled release nitrogen fertilizer (coated urea) on growth, yield, and nitrogen fixation of soybean plants

Abstract

The objective of these studies is to increase the productivity of soybean [ Glycine max (L.) Merr. cv. Enrei] with good quality by the application of controlled release nitrogen fertilizers. Soybean was grown in an upland field converted from a drained paddy field in Niigata. The fertilizer treatments were as follows: (a) control, conventional basal dressing of ammonium sulfate (16 kg N/ha); (b) deep placement, deep placement of coated urea, 100 day type (100 kg N/ha) with basal dressing of ammonium sulfate (16 kg N/ha); (c) top dressing, top dressing of coated urea, 70 day type (100 kg N/ha) just before the flowering stage with basal dressing of ammonium sulfate (16 kg N/ha).We employed the following methods and materials: "lSN-labeled fertilizers," to estimate the amount of N derived from fertilizers; "N-balance method" using the nodulating and non-nodulating isogenic line cv. T202 and T201, to estimate the amount of fixed N~ by root nodules; "relative ureide method" to determine the relative content of ureide-N in the root bleeding sap, in order to estimate the activity of the root nodules.The accumulation of dry matter and total N was the highest in the plants with the deep placement treatment, in which the promotion of leaf growth and retardation of senescence were observed during the maturation stage. The seed yield in this treatment which was 424 g/m 2, surpassed those in the control (373 g/m 2) and the top dressing (359 g/m s) treatments. The absorption efficiency of fertilizer N in the deep placement treatment was 49~o, which was much higher than that in the top dressing treatment (27~o). However, the contribution of fertilizer N to the total N absorption was found to be low at 16~o in the deep placement, and 11~o in the top dressing treatment at the R7 stage. In the deep placement treatment, a marked increase in N accumulation in shoots was observed especially from the R3 till R7 stages. The N-balance of the nodulating and non-nodulating cv. T202 and T201 at the R7 stage suggested that more than 80% of the accumulated N was derived from the fixed N2 by root nodules. On the other hand, in the top dressing treatment, the amount of N accumulated during the R3 to R7 stages was lower than that in the other treatments, possibly due to the depression of N2 fixation by top dressing.Abbreviations: DW: dry weight; cu-100: coated urea, I00 day type; cu-70: coated urea, 70 day type; Cont.: control; Deep pl.: deep placement of cu-100; Top dr.: top dressing of cu-70; LAI: leaf area index; DAS: days after sowing. Y. TAKAHASHI et al.The results suggested that the deep placement of coated urea as basal application improved soybean growth, and did not depress markedly the nitrogen fixation activity during the maturation stage, hence the increase of seed yield. Top dressing of coated urea inhibited the nodule activity after the R3 stage, and consequently the seed yield did not increase.

Higher diversity and abundance of denitrifying microorganisms in environments than considered previously

“…We used cropland soil (Takahashi et al, 1991), rice paddy soil (Itoh et al, 2013), forest soils (Urakawa et al, 2015) and lake sediment (Abe et al, 2000) as described below. All soil samples were collected in triplicate at 5-10 cm depth from each experimental site, and lake sediment was sampled in triplicate at 10 cm depth from the sediment surface using an Ekman sampler.…”

“…Various environmental samples from terrestrial habitats were used, including a cropland soil (Andosol) applied with an organic fertilizer , a cropland soil (Gray Lowland Soil, Eutric Fluvisol) applied with an organic or urea fertilizer (Takahashi et al, 1991), paddy soils from flooded and non-flooded seasons (Gray Lowland Soil, Eutric Fluvisol) (Itoh et al, 2013), two natural forest soils (Brown Forest soil and Andosol) (Urakawa et al, 2015), a planted forest soil (Brown Forest soil) (Oda et al, 2009) and a lake sediment (Abe et al, 2000). Environmental DNA was extracted as previously described.…”

Effect of placement of coated urea fertilizer on root growth and rubidium uptake activity in soybean plant

“…Top dressing of CU-70 stimulated the growth and Rb uptake activity of the roots especially in the upper layers. However since this treatment strongly depressed N2 fixation during the maturation stage, seed yield could not be improved compared to the deep placement under field conditions as described before (Takahashi et al 1991).…”

“…Fertilizer application was designed as follows: (a) control, basal dressing of ammonium sulfate (16 kg N/ha); (b) deep placement, basal dressing of ammonium sulfate (16 kg N/ha), and deep placement of CU-100 (100 kg N/ha); (c) top dressing, basal dressing of ammonium sulfate (16 kg N/ ha) and top dressing of CU-70 (100 kg N/ha). The application methods were the same as those described in the previous study (Takahashi et al 1991). On May 28, 3 d before plowing, CU-100 was applied under the seed-placement lines along the ridge at a depth of about 20 cm using the fertilizer injector devised by Shioya (1985).…”

“…The soil is a fine-textured Gray Lowland soil (gray type) and the chemical properties of the soil were described in the previous paper (Takahashi et al 1991). Fertilizer application was designed as follows: (a) control, basal dressing of ammonium sulfate (16 kg N/ha); (b) deep placement, basal dressing of ammonium sulfate (16 kg N/ha), and deep placement of CU-100 (100 kg N/ha); (c) top dressing, basal dressing of ammonium sulfate (16 kg N/ ha) and top dressing of CU-70 (100 kg N/ha).…”