Effects of deep placement of controlled-release nitrogen fertilizer on soybean growth and yield under sulfur deficiency

Figures & data

Table 1. Effects of S supply and deep placement of coated urea on SPAD values in leaves at the flowering stage

Date	S1000 (+)	S100 (+)	S30 (+)	S1000 (–)	S100 (–)	S30 (–)
16 June	32.4 ± 2.2	31.8 ± 2.2*	32.0 ± 2.8*	30.1 ± 1.9	29.0 ± 1.7	30.6 ± 2.0
29 June	36.3 ± 4.0	39.3 ± 4.0	38.5 ± 4.0*	36.8 ± 3.6	37.5 ± 3.6	35.0 ± 3.6
7 July	39.8 ± 2.2	37.3 ± 3.1	38.9 ± 43.1	36.6 ± 3.1	35.3 ± 2.7	37.7 ± 2.3
13 July	39.4 ± 2.9 ^a	35.6 ± 3.4 ^b	37.6 ± 4.0	37.1 ± 2.0	34.9 ± 1.6	34.2 ± 1.5

Soybean plants were grown with (+) or without (–) deep placement of coated urea at sulfate concentrations of 30, 100, and 1000 μM. At the flowering stage (June 16 to July 13), SPAD values were determined at the center part of leaves in trifoliates at the second node from the top and averaged per trifoliate. Means of six biological replicates are shown.

Asterisks indicate significant difference between Deep+ and Deep – at the same concentration of sulfate on the same day, and different letters (a, b) indicate significant difference between S1000 (+) and S100 (+) using a Student’s t-test (P < 0.05).

Figure 1. Effects of S supply and deep placement of coated urea on shoot biomass at the developing stage. Shoot dry weights were determined 40 days after sowing. Means ± standard deviations of four biological replicates are shown. The asterisk indicates a significant difference using a Student’s t-test (P < 0.05)

Figure 2. Effects of S supply and deep placement of coated urea on soybean seed yield and yield components at the harvest stage. Mature dry seeds were harvested, and seed dry weight per plant (a), hundred-seed weight (b), seed number per pod (c), and pod number per plant (d) were determined. Means ± standard deviations of four biological replicates are shown. Asterisks indicate significant differences using a Student’s t-test (P < 0.05)

Figure 3. Effects of S supply and deep placement of coated urea on N concentrations and content in shoots of soybean at developing stage and in seeds at harvest stage. N concentration in shoots (a) and N content in shoots per plant (b) were determined 40 days after sowing, and N concentration in mature dry seeds (c) and N content in mature dry seeds per plant (d) were determined at the harvest stage. Means ± standard deviations of four biological replicates are shown. Asterisks indicate significant differences using a Student’s t-test (P < 0.05)

Figure 4. Effects of S supply and deep placement of coated urea on S concentrations and content in soybean shoots at the developing stage and in seeds at the harvest stage. S concentration in shoots (a) and the S content in shoots per plant (b) were determined at 40 days after sowing, and S concentration in mature dry seeds (c) and the S content in mature dry seeds per plant (d) were determined at the harvest stage. Means ± standard deviations of four biological replicates are shown. Asterisks indicate significant differences using a Student’s t-test (P < 0.05)

Table 2. Ureide, amide, and nitrate concentration and relative ureide-N content in xylem sap

Ureide concentration (mM)
Days	S1000 (+)	S100 (+)	S30 (+)	S1000 (–)	S100 (–)	S30 (–)
40	12.2 ± 1.6	12.7 ± 1.8	21.6 ± 2.4	No data	16.7 ± 4.0	15.9 ± 5.5
67	8.4 ± 0.4	3.6 ± 1.6	4.8 ± 1.4	9.0 ± 2.9	12.1 ± 2.7	7.6 ± 3.1
Amide concentration (mM)
Days	S1000 (+)	S100 (+)	S30 (+)	S1000 (–)	S100 (–)	S30 (–)
40	7.4 ± 3.1	7.8 ± 1.2	6.9 ± 0.7	No data	5.4 ± 1.0	6.2 ± 1.3
67	3.4 ± 0.1	3.0 ± 0.6	3.3 ± 1.0	2.3 ± 0.6	2.6 ± 0.3	3.3 ± 0.3
Nitrate concentration (mM)
Days	S1000 (+)	S100 (+)	S30 (+)	S1000 (–)	S100 (–)	S30 (–)
40	0.28 ± 0.36	0.25 ± 0.18	0.14 ± 0.20	No data	0.62 ± 0.66	0.18 ± 0.17
67	0.68 ± 0.00	1.43 ± 0.85	0.27 ± 0.28	0.28 ± 0.25	0.48 ± 0.28	0.58 ± 0.21
Relative ureide-N content (%)
Days	S1000 (+)	S100 (+)	S30 (+)	S1000 (–)	S100 (–)	S30 (–)
40	77.1 ± 6.4	76.0 ± 2.3	86.0 ± 2.3	No data	85.8 ± 1.4	82.8 ± 1.2
67	81.9 ± 1.2*	63.9 ± 9.2*	72.1 ± 10.5	87.6 ± 1.3^a	89.3 ± 0.7	76.1 ± 0.6^b

Xylem sap of soybean plants with (+) or without (-) deep placement of coated urea was sampled 40 and 67 days after sowing. Sulfate concentrations in the medium were 1000, 100, or 30 μM. Means ± 3 standard deviations of biological replicates are shown. Asterisks indicate significant difference between Deep+ and Deep – at the same concentration of sulfate on the same day, and different letters (a, b) indicate significant difference between S1000 (-) and S30 (-) using a Student’s t-test (P < 0.05).