Key soil nutrient requirements for different yield levels in North China

Figures & data

Table 1. Soil, climate, and crop details at the different study sites

Study site	Location	Crop cycle	Annual precipitation (mm/yr)	Annual temperature (°C)	Soil texture
Juye	35°15′N, 115°57′E	wheat-maize	741	13.5	Loam
Donggang	35°24′N, 119°24′E	wheat-maize	916	12.6	Loam
Linyi	37°22′N, 116°55′E	wheat-maize	554	12.6	Loam
Lijin	37°32′N, 118°17′E	wheat-maize	578	13.1	Loam
Laiyang	36°54′N, 120°41′E	wheat-maize	800	11.2	Loam
Daiyue	36°29′N, 117°29′E	wheat-maize	697	13.0	Loam
Pingyuan	37°09′N, 116°26′E	wheat-maize	600	12.6	Loam
Huimin	37°48′N, 117°30′E	wheat-maize	589	12.2	Loam
Longkou	37°39′N, 120°33′E	wheat-maize	630	11.6	Loam
Caoxian	34°53′N, 115°38′E	wheat-maize	678	14.3	Loam

Table 2. Number of samples collected at each study site

	Sample site
Yield levels	Juye	Linyi	Lijin	Donggang	Laiyang	Daiyue	Caoxian	Huimin	Longkou	Pingyuan	Total
High-level	33	45	12	40	27	16	16	40	27	60	316
Medium-level	20	25	18	7	20	19	15	20	20	0	164
Low-level	4	0	18	13	8	16	14	0	12	0	85
Total	57	70	48	60	55	51	45	60	59	60	565

Table 3. Soil chemical properties at each study site

Soil chemical property^‡	Study site
	Juye	Donggang	Linyi	Lijin	Laiyang	Daiyue	Pingyuan	Huimin	Longkou	Caoxian
SOC (g/kg)	11.25 ± 0.99^f†	11.93 ± 0.68^e	13.23 ± 1.31^d	10.51 ± 1.27^g	10.07 ± 1.15^g	11.16 ± 1.33^f	14.41 ± 1.43^ab	13.70 ± 0.41^cd	14.72 ± 0.68^a	13.96 ± 1.26^bc
TN (g/kg)	0.84 ± 0.06^c	0.75 ± 0.17^d	0.52 ± 0.09^f	0.38 ± 0.10^g	0.61 ± 0.09^e	0.76 ± 0.16^d	1.01 ± 0.06^b	0.89 ± 0.03^c	1.29 ± 0.28^a	0.71 ± 0.04^d
AN (mg/kg)	83.46 ± 7.09^b	71.48 ± 4.77^d	78.05 ± 9.52^c	62.53 ± 4.74^e	56.43 ± 3.05^f	66.38 ± 4.12^de	84.10 ± 5.57^b	76.70 ± 6.18^c	88.77 ± 7.17^ab	89.77 ± 3.78^a
AP (mg/kg)	32.43 ± 2.54^c	44.94 ± 3.26^b	23.40 ± 2.09^de	17.36 ± 2.61^g	24.24 ± 2.37^d	21.94 ± 1.36^ef	21.90 ± 1.57^ef	23.14 ± 0.89^def	48.54 ± 3.97^a	21.02 ± 1.93^f
AK (mg/kg)	117.9 ± 8.90^d	79.4 ± 7.91^f	184.5 ± 11.44^a	129.7 ± 9.89^c	88.1 ± 6.63^e	79.0 ± 2.62^f	140.8 ± 5.54^b	115.1 ± 5.67^d	132.1 ± 7.25^c	145.1 ± 8.81^b
Soil pH	7.88 ± 0.14^bc	6.88 ± 0.59^e	7.87 ± 0.18^bc	8.11 ± 0.18^ab	6.75 ± 0.35^e	6.68 ± 0.31^ef	7.32 ± 0.21^d	7.83 ± 0.17^c	6.46 ± 0.76^f	8.19 ± 0.13^a
Soil Zn (mg/kg)	0.78 ± 0.05^f	1.14 ± 0.18^d	1.02 ± 0.06^de	0.44 ± 0.04^g	0.89 ± 0.11^ef	1.12 ± 0.15^d	1.85 ± 0.06^b	1.39 ± 0.04^c	5.97 ± 0.41^a	1.34 ± 0.06^c
Soil Cu (mg/kg)	1.51 ± 0.14^b	1.17 ± 0.21^cde	1.14 ± 0.08^de	0.75 ± 0.07^f	1.13 ± 0.13^de	1.07 ± 0.15^e	1.25 ± 0.20^c	1.42 ± 0.10^b	2.20 ± 0.23^a	1.20 ± 0.14^cd

^†Different lowercase letters in same row denote significant differences between treatment groups (p < 0.05).

^‡SOC: soil organic carbon, TN: total nitrogen, AN: available nitrogen, AP: available phosphorus, AK: available potassium.

Figure 1. Average annual total yields at the different sample sites

Figure 2. Correlations between total annual yield and SOC

Figure 3. Correlations between total annual yield and soil total N

Figure 4. Correlations between total annual yield and soil available N, P, and K

Figure 5. Correlation between total annual yield and soil pH

Figure 6. Correlations between total annual yield and soil Zn and Cu

Table 4. Loading matrix, eigenvalues, and contributing ratios of the principal components

	H-level		M-level		L-level
Factors	PC1^‡	PC2	PC1	PC2	PC1	PC2	PC3
SOC^†	0.74	0.35	0.34	0.22	0.79	0.19	0.27
Soil TN	0.36	0.65	0.35	0.13	0.41	0.56	−0.16
Soil AN	0.44	0.51	0.60	0.46	0.66	0.58	0.26
Soil AP	0.34	0.38	0.27	0.25	0.45	−0.03	0.78
Soil AK	0.33	0.28	−0.16	0.21	0.13	0.41	−0.21
Soil pH	−0.38	−0.30	−0.26	−0.61	−0.53	−0.20	−0.34
Soil Zn	−0.19	0.14	0.47	−0.17	0.29	0.29	0.14
Soil Cu	0.21	0.09	−0.38	0.13	0.17	0.43	0.27
Eigenvalues	4.26	2.77	4.68	2.64	3.76	2.44	1.03
Contributing ratios (%)	53.25	34.63	58.53	33.01	47.00	30.50	12.88
Accumulated contributing ratios (%)	53.25	87.88	58.53	91.54	47.00	77.50	90.38

† SOC: soil organic carbon, TN: total nitrogen, AN: available nitrogen, AP: available phosphorus, AK: available potassium

‡ Principal components (PC) in different yield levels.