Ammonium alleviates iron deficiency of drip-irrigated rice seedlings in low soil temperature in calcareous soil

Figures & data

Figure 1. Effect of nitrogen forms (N) on rhizosphere soil pH (A) and rhizosphere soil DTPA-Fe (B) of rice cultivars (G) in different soil temperatures (T). Error bars represent SE (n = 4). Columns within each cultivar the same letter are not significantly different at 5% according to Duncan’s multiple range test. Abbreviations: Fe-efficient and Fe-inefficient, Fe-efficient genotype rice (O. sativa L. cv. T43) and Fe-inefficient genotype rice (O. sativa L. cv. T04). NAM and NNI, ammonium nitrogen was (NH₄)₂SO₄+ 2.0% DCD and nitrate nitrogen was Ca(NO₃)₂ + 2.0% DCD, respectively. T24 and T18, soil optimum temperature was 24 ± 2°C and soil low temperature was 18 ± 2°C, respectively. *** and ns indicate significant differences at p < 0.1% and p ≥ 5%.

Figure 2. Effect of nitrogen forms (N) on root ferric chelate reductase activity (A) and leaf SPAD value (B) of rice cultivars (G) in different soil temperatures (T). Error bars represent SE (n = 4). Columns within each cultivar the same letter are not significantly different at 5% according to Duncan’s multiple range test. Abbreviations: Fe-efficient and Fe-inefficient, Fe-efficient genotype rice (O. sativa L. cv. T43) and Fe-inefficient genotype rice (O. sativa L. cv. T04). NAM and NNI, ammonium nitrogen was (NH₄)₂SO₄+ 2.0% DCD and nitrate nitrogen was Ca(NO₃)₂ + 2.0% DCD, respectively. T24 and T18, soil optimum temperature was 24 ± 2°C and soil low temperature was 18 ± 2°C, respectively. *, **, *** and ns indicate significant differences at P < 5%, P < 1%, p < 0.1% and p ≥ 5%.

Figure 3. Effect of nitrogen forms (N) on shoot dry weight (A), root dry weight (B) and number of tillers (C) of rice cultivars (G) in different soil temperatures (T). Error bars represent SE (n = 4). Columns within each cultivar the same letter are not significantly different at 5% according to Duncan’s multiple range test. Abbreviations: Fe-efficient and Fe-inefficient, Fe-efficient genotype rice (O. sativa L. cv. T43) and Fe-inefficient genotype rice (O. sativa L. cv. T04). NAM and NNI, ammonium nitrogen was (NH₄)₂SO₄+ 2.0% DCD and nitrate nitrogen was Ca(NO₃)₂ + 2.0% DCD, respectively. T24 and T18, soil optimum temperature was 24 ± 2°C and soil low temperature was 18 ± 2°C, respectively. *, **, *** and ns indicate significant differences at P < 5%, P < 1%, p < 0.1% and p ≥ 5%.

Table 1. Effects of different nitrogen forms (N) on root surface area and root activity of rice cultivars (G) in different soil temperatures (T).

Rice cultivars	Nitrogen forms	Soil temperatures	SurfArea (cm^2)	Total absorption area (cm^2)	Active absorption area (cm^2)
Fe-efficient	NAM	T24	170 ± 19a	230 ± 34a	96 ± 4a
		T18	123 ± 23b	179 ± 23b	74 ± 9b
	NNI	T24	74 ± 7c	132 ± 9c	61 ± 10b
		T18	37 ± 2d	98 ± 10d	42 ± 8c
Fe-inefficient	NAM	T24	141 ± 9a	233 ± 36a	77 ± 7a
		T18	119 ± 7b	172 ± 17b	55 ± 9b
	NNI	T24	54 ± 5c	112 ± 7c	52 ± 0b
		T18	30 ± 6d	74 ± 6d	25 ± 3c
Three-way ANOVA (Significance)
Rice cultivars (G)			**	ns	***
Nitrogen form (N)			***	***	***
Soil temperature (T)			***	***	**
G × N			ns	ns	ns
G × T			ns	ns	ns
N × T			ns	ns	ns
G × N × T			ns	ns	ns

Within each cultivar, values followed by the same letter in a column are not significantly different according to Duncan’s Multiple Range Test. Abbreviations: Fe-efficient and Fe-inefficient, Fe-efficient genotype rice (O. sativa L. cv. T43) and Fe-inefficient genotype rice (O. sativa L. cv. T04). NAM and NNI, ammonium nitrogen was (NH₄)₂SO₄+ 2.0% DCD and nitrate nitrogen was Ca(NO₃)₂+ 2.0% DCD, respectively. T24 and T18, soil optimum temperature was 24 ± 2°C and soil low temperature was 18 ± 2°C, respectively. **, *** and ns indicate significant differences at P < 1%, p < 0.1% and p ≥ 5%.

Table 2. Effects of different nitrogen forms (N) on Fe uptake of rice cultivars (G) in different soil temperatures (T).

Rice cultivars	Nitrogen forms	Soil temperatures	Fe concentration (µg g^−1)		Fe uptake (µg hill^−1)
			Shoots	Roots	Shoots	Roots
Fe-efficient	NAM	T24	168 ± 17b	1023 ± 102c	651 ± 62a	401 ± 30b
		T18	160 ± 11b	2041 ± 370b	371 ± 53b	566 ± 78a
	NNI	T24	109 ± 14c	1700 ± 196b	194 ± 15d	289 ± 17c
		T18	285 ± 33a	3342 ± 306a	289 ± 11c	362 ± 50bc
Fe-inefficient	NAM	T24	136 ± 5b	1267 ± 203c	606 ± 62a	462 ± 66b
		T18	148 ± 17b	1899 ± 154b	499 ± 79b	598 ± 14a
	NNI	T24	141 ± 4b	1846 ± 223b	136 ± 10c	165 ± 30c
		T18	227 ± 13a	3849 ± 466a	138 ± 18c	169 ± 35c
Three-way ANOVA (Significance)
Rice cultivars (G)			*	ns	ns	**
Nitrogen form (N)			***	***	***	***
Soil temperature (T)			***	***	**	***
G × N			ns	ns	**	***
G × T			*	ns	ns	ns
N × T			***	***	***	**
G × N × T			***	ns	**	ns

Within each cultivar, values followed by the same letter in a column are not significantly different according to Duncan’s Multiple Range Test. Abbreviations: Fe-efficient and Fe-inefficient, Fe-efficient genotype rice (O. sativa L. cv. T43) and Fe-inefficient genotype rice (O. sativa L. cv. T04). NAM and NNI, ammonium nitrogen was (NH₄)₂SO₄+ 2.0% DCD and nitrate nitrogen was Ca(NO₃)₂ + 2.0% DCD, respectively. T24 and T18, soil optimum temperature was 24 ± 2°C and soil low temperature was 18 ± 2°C, respectively. *, **, *** and ns indicate significant differences at P < 5%, P < 1%, p < 0.1% and p ≥ 5%.