Optimizing nitrogen fertilizer and straw management promote root extension and nitrogen uptake to improve grain yield and nitrogen use efficiency of winter wheat (Triticum aestivum L.)

Figures & data

Figure 1. Monthly mean rainfall, mean maximum and minimum temperatures during the wheat-growing season from 2020 to 2022 in Nanjing, China.

Table 1. The soil properties at the experimental site at the beginning of the experiment in two wheat growth seasons.

Soil layer	Organic matter	Total N	Nitrite N	Olsen-P	Exchangeable K	pH	Bulk density
cm	g kg^−1	g kg^−1	mg kg^−1	mg kg^−1	mg kg^−1		g cm^−3
2020–2021
0–10	22.81	1.19	13.08	13.13	88.37	6.62	1.25
10–20	21.37	1.13	12.65	12.33	81.13	6.73	1.28
20–40	20.11	1.03	10.84	11.06	72.88	6.88	1.37
40–60	15.62	0.87	7.78	10.25	66.71	6.95	1.44
60–100	13.65	0.72	6.24	10.12	61.88	7.05	1.35
2021–2022
0–10	23.56	1.24	13.85	13.71	95.13	6.74	1.22
10–20	22.16	1.15	12.74	12.56	84.62	6.77	1.25
20–40	21.08	0.96	10.65	11.24	75.61	6.93	1.33
40–60	14.77	0.85	7.73	10.18	59.54	6.89	1.41
60–100	13.18	0.68	6.28	10.14	57.49	7.12	1.29

Table 2. Nitrogen application rates and basal nitrogen application stage under different nitrogen fertilizer managements.

			N application stage and rate (kg N ha^−1)
		N rate	Basal nitrogen		Top-dressed nitrogen
Nitrogen	Straw management	(kg N ha^−1)	Seeding	3-leaf	Jointing	Booting
BN240	NS	240	120	–	72	48
	SR	240	120	–	72	48
	SP	240	120	–	72	48
TN240	NS	240	–	120	72	48
	SR	240	–	120	72	48
	SP	240	–	120	72	48
BN180	NS	180	60	–	72	48
	SR	180	60	–	72	48
	SP	180	60	–	72	48
TN180	NS	180	–	60	72	48
	SR	180	–	60	72	48
	SP	180	–	60	72	48
N0	NS	0	–	–	–	–
	SR	0	–	–	–	–
	SP	0	–	–	–	–

Table 3. Effects of straw and nitrogen fertilizer managements on grain yield, N accumulation and N recovery efficiency (NRE).

		Spikes		1000-grain weight	Grain yield	N accumulation	NRE
Nitrogen	Straw	(×10^4 ha^−1)	Grain number	(g)	(kg ha^−1)	(kg ha^−1)	(%)
2020–2021
BN240	NS	363.33ab	45.64c	42.37c	6346.13c	159.8 cd	37.37e
	SR	356.33b	46.38bc	44.32ab	6601.60bc	169.05bc	39.45d
	SP	369.67ab	47.67b	45.25a	6831.43b	177.76b	40.22d
TN240	NS	376.33a	47.69b	42.47c	6480.17c	163.06c	38.73de
	SR	370.33ab	48.38ab	44.48ab	6904.30ab	172.91b	41.06 cd
	SP	383.33a	49.20a	45.86a	7134.17a	183.69a	42.69c
BN180	NS	329.67d	43.33d	43.18bc	5501.20e	142.26e	40.08d
	SR	302.33e	42.96e	43.58b	5230.10f	147.16de	40.44d
	SP	322.33d	43.62d	45.02ab	5975.43d	158.22 cd	42.77c
TN180	NS	350.67bc	45.09c	43.65b	5810.43d	147.28de	42.87c
	SR	327.67d	46.36bc	44.80ab	5840.20d	156.98d	45.90b
	SP	342.33c	47.22b	46.01a	6459.57c	166.38c	47.30a
2021–2022
BN240	NS	385.33b	43.91b	41.71d	6621.74c	165.85c	37.39e
	SR	374.33bc	44.59ab	43.38c	7063.29b	172.42bc	40.86d
	SP	385.67b	44.82ab	44.26bc	7248.74ab	176.32b	41.28d
TN240	NSR	397.33ab	44.31ab	41.02d	6821.75bc	171.65bc	39.81de
	SR	388.67b	45.47a	44.15bc	7210.58ab	178.84b	43.53c
	SP	411.67a	45.95a	45.61b	7523.67a	188.24a	46.25b
BN180	NS	346.33d	40.73d	41.27d	6035.78de	146.26e	38.97de
	SR	316.67e	40.48d	43.19c	5532.48e	148.66e	41.28d
	SP	348.33d	41.25c	44.72b	6209.73d	156.74d	44.17c
TN180	NS	365.67c	42.18bc	42.67c	6073.41de	154.45d	43.52c
	SR	343.67d	43.57b	45.69b	6229.45d	158.23 cd	46.59b
	SP	369.67c	44.48ab	47.27a	6770.21bc	164.71c	48.59a
Year		*	*	ns	*	*	ns
Nitrogen		**	*	*	**	*	**
Straw		*	*	**	*	*	*
N × S		*	ns	*	*	*	*
Y × N		*	ns	*	ns	ns	ns
Y × S		ns	ns	ns	ns	ns	ns
Y × N × S		ns	ns	ns	ns	ns	ns

NS, SR and SP refer to no straw return, straw return by rotary tillage and straw return by ploughing respectively.

NRE refer N recovery efficiency, respectively. Lower case letters refer to significant difference between treatments (p < 0.05), values are means (n = 3). *, ** and ns are significant at p < 0.05, p < 0.01 and not significant, respectively.

Table 4. Effects of straw and nitrogen fertilizer managements on N accumulation and N accumulation rate during different growth periods.

		N accumulation（kg ha^−1）				N accumulation rate（kg ha^−1d^−1）
Treatment		S-T	T-J	J-A	A-M	S-T	T-J	J-A	A-M
2020–2021
BN240	NS	20.56a	28.07ab	84.71bc	26.46c	0.82ab	0.29a	2.07d	0.63c
	SR	20.29ab	26.30bc	94.17ab	28.29b	0.81b	0.27ab	2.30c	0.66b
	SP	21.05a	27.46b	100.25a	28.99b	0.84a	0.28a	2.45b	0.67b
TN240	NS	19.92ab	27.86ab	87.77b	27.48bc	0.80b	0.28a	2.19c	0.64bc
	SR	19.39b	27.63ab	95.90ab	29.96b	0.78b	0.28a	2.46b	0.68b
	SP	20.02ab	29.02a	102.37a	32.27a	0.80b	0.30a	2.62a	0.73a
BN180	NS	20.65a	25.25c	75.45d	20.91e	0.83a	0.26b	1.80e	0.52e
	SR	19.83b	23.22e	80.42c	23.69d	0.79b	0.24b	1.87de	0.58d
	SP	20.21ab	25.69c	87.04bc	25.29c	0.81b	0.26b	2.02d	0.62c
TN180	NS	19.92ab	25.84c	78.09c	23.43d	0.80b	0.26b	1.90de	0.57d
	SR	19.39b	24.28d	87.61bc	25.70c	0.78b	0.25b	2.09d	0.60 cd
	SP	20.02ab	26.34bc	92.02b	28.00b	0.80b	0.27ab	2.18c	0.65b
2021–2022
BN240	NS	20.35a	18.41c	100.68b	26.40c	0.75a	0.18b	2.65b	0.60 cd
	SR	19.66ab	17.64 cd	106.60ab	28.53bc	0.73a	0.17bc	2.73ab	0.63c
	SP	20.33a	18.26c	107.35a	30.38b	0.75a	0.18b	2.75ab	0.68b
TN240	NS	19.20b	21.54b	103.05b	27.97c	0.71b	0.21ab	2.71ab	0.64bc
	SR	18.53c	23.52a	105.91ab	30.95b	0.68c	0.23a	2.72ab	0.69b
	SP	19.24b	24.07a	110.65a	34.44a	0.71b	0.24a	2.84a	0.77a
BN180	NS	19.59ab	15.31e	89.01c	22.35e	0.73ab	0.15c	2.23d	0.55de
	SR	19.41ab	13.88f	86.83c	21.54f	0.72b	0.15c	2.22d	0.56d
	SP	19.80a	15.18e	95.37bc	26.39c	0.73ab	0.15c	2.33 cd	0.63c
TN180	NS	19.20b	16.28d	95.17bc	23.80d	0.71b	0.16bc	2.44c	0.57d
	SR	18.53c	17.61 cd	96.43bc	25.66 cd	0.69c	0.17bc	2.41c	0.58d
	SP	19.24b	17.99c	100.79b	26.69c	0.71b	0.18b	2.52bc	0.61c
Year		ns	*	*	ns	*	*	*	ns
Nitrogen		ns	ns	*	*	ns	ns	**	*
Straw		*	*	**	**	*	*	*	**
N×S		ns	ns	*	*	*	ns	*	*
Y×N		ns	ns	ns	ns	ns	ns	ns	ns
Y×S		ns	ns	ns	ns	ns	*	ns	ns
Y×N×S		ns	ns	ns	ns	ns	ns	ns	ns

NS, SR and SP refer to no straw return, straw return by rotary tillage and straw return by ploughing respectively.

S-T, T-J, J-A and A-M refer to the growth period of sowing to 3-leaf stage, 3-leaf stage to jointing stage, jointing stage to anthesis stage and anthesis stage to maturity stage respectively. Lower case letters refer to significant difference between treatments (p < 0.05), values are means (n = 3). *, ** and ns are significant at p < 0.05, p < 0.01 and not significant, respectively.

Figure 2. Effects of straw and nitrogen fertilizer managements on root biomass at jointing (A, B), anthesis (C, D) and maturity (E, F) in 2020–2022. NS, SR and SP refer to no straw return, straw return by rotary tillage and straw return by ploughing, respectively. * and ** indicate significant differences at the 0.05 and 0.01 levels, respectively; ns indicates no significant difference. Whiskers on the top of the bars indicate standard error.

Figure 3. Effects of straw and nitrogen fertilizer managements on root weight density at jointing, anthesis and maturity in 2021–2022. NS, SR and SP refer to no straw return, straw return by rotary tillage and straw return by ploughing, respectively. The four rows from top to bottom show the root weight density under N management for BN240 (A, B, C), TN240 (D, E, F), BN180 (G, H, I) and TN180 (J, K, L), respectively. * and ** indicate significant differences at the 0.05 and 0.01 levels, respectively; ns indicates no significant difference. Whiskers on the top of the bars indicate standard error.

Figure 4. Effects of straw and nitrogen fertilizer managements on ¹⁵N residue content in different soil layers at jointing, anthesis and maturity stages in 2021–2022. NS, SR and SP refer to no straw return, straw return by rotary tillage and straw return by ploughing, respectively. The four rows from top to bottom show the root weight density under N management for BN240 (A, B, C), TN240 (D, E, F), BN180 (G, H, I) and TN180 (J, K, L), respectively. * and ** indicate significant differences at the 0.05 and 0.01 levels, respectively; ns indicates no significant difference. Whiskers on the top of the bars indicate standard error.

Figure 5. Effects of straw and nitrogen fertilizer managements on inorganic activity, microbial biomass C and microbial biomass N in the 0–20 cm soil layer at tillering, jointing and anthesis in 2021–2022. NS, SR and SP refer to no straw return, straw return by rotary tillage and straw return by ploughing, respectively. * and ** indicate significant differences at the 0.05 and 0.01 levels, respectively; ns indicates no significant difference. Whiskers on the top of the bars indicate standard error.

Figure 6. Effects of straw and nitrogen fertilizer managements on the fates of ¹⁵N fertilizer in 2021–2022. NS, SR and SP refer to no straw return, straw return by rotary tillage and straw return by ploughing, respectively. Whiskers on the top of the bars indicate standard error.