Effect of long-term fertilisation of Calcisols on organic carbon sequestration in marine climate in Estonia

Figures & data

Table 1. Fertilisation: levels and quantities (NPK kg ha⁻¹ and FYM* Mg ha⁻¹) in the long-term NPK fertilisation trial in 1975–2021 in Kuusiku.

Crop rotation	N2	N3	N4	P2	P3	K2	K3	FYM1	FYM2
Potato**	80	120	160	36	54	70	105	30	60
Sping barley	70	105	140	18	27	50	75	0	0
Sprig barley (unders)	40	60	80	52	78	60	90	0	0
1y forage grasses	0	0	0	0	0	0	0	0	0
2y forage grasses	80	120	160	0	0	60	90	0	0
Winter rye	90	135	180	26	39	60	90	0	0
Average per year	60	90	120	22	33	50	75	5	10

*- The nutrient content of manure (FYM): N (nitrogen), 2.8 kg Mg⁻¹; P (phosphorus), 0.6 kg Mg⁻¹; K (potassium), 4.7 kg Mg⁻¹.

**- The potatoes were in crop rotation until 2018.

Table

N60P22K50	N60P22K50 + FYM30	N90P22K50 + FYM60
N90P22K50	N90P22K50 + FYM30	N120P33K75 + FYM60
N90P33K75	N120P33K75 + FYM30	N0P0K0
N120P33K75	N60P22K50+ FYM60

Figure 1. Characterisation of the weather: T – air temperature, °C, mm – precipitation, mm, during the trial period 1976–2021 in Kuusiku.

Figure 2. Effect of long-term fertilisation (NPK kg ha⁻¹ and manure (FYM) Mg ha⁻¹) on soil organic carbon concentration, SOC%, in the NPK fertilisation experiment of the crop rotation; LSD95% – level of 95% confidence in the LSD0.05 (LSD; least significant difference) test MS Excel.

Table 2. Overview of crop yield changes in the long-term fertilisation experiment of the crop rotation in the years 1976–1995 and 1996–2021 on Calcisol loamy soil in Kuusiku.

Crop rotation	Fertilisation*	Yield of vegetation periods, Mg ha^−1		Difference, %
		1976–1995	1996–2021
Spring barley	N0P0K0	2.0	2.2	10.0
	N90P26K58	3.4	4.4	29.4
	N90P26K58 + FYM30	3.4	4.8	41.2
	N90P26K58 + FYM60	3.4	4.9	44.1
Spring barley + under sown	N0P0K0	1.4	1.3	−7.1
	N90P26K58	3.2	3.6	12.5
	N90P26K58 + FYM30	3.3	3.8	15.2
	N90P26K58 + FYM60	3.4	3.9	14.7
1y forage grasses	N0P0K0	5.7	4.0	−29.8
	N90P26K58	5.9	5.8	−1.7
	N90P26K58 + FYM30	6.2	6.5	4.8
	N90P26K58 + FYM60	6.2	6.3	1.6
2y forage grasses	N0P0K0	3.5	1.6	−54.3
	N90P26K58	6.1	5.1	−16.4
	N90P26K58 + FYM30	6.2	5.7	−6.6
	N90P26K58 + FYM60	6.3	5.4	−14.3
Winter rye	N0P0K0	1.9	2.0	5.3
	N90P26K58	3.8	3,7	−5.1
	N90P26K58 + FYM30	4.0	3.7	−7.5
	N90P26K58 + FYM60	3.9	4.0	2.6
Potato	N0P0K0	16.3	20.7	27.0
	N90P26K58	26.2	35.4	34.9
	N90P26K58 + FYM30	28.8	39.1	35.8
	N90P26K58 + FYM60	29.7	38.0	27.9

*- 000 – unfertilised; NPK (N-Nitrogen, P-Phosphorus, K-Potassium) is the average of NPK fertilisation variants of N60P22K50, N90P22K50 and N120P33K75 kg ha⁻¹, because changes in soil organic carbon concentration – SOC% were marginal there; manure: FYM 30 Mg ha⁻¹ and FYM 60 Mg ha⁻¹.

Table 3. The effect of fertilisation (NPK kg ha⁻¹ and manure (FYM) Mg ha⁻¹) on the content of stable and labile forms of organic carbon in sandy loam Calcisols in the 0–0.20 and 0.20–0.40 m soil layer in Kuusiku.

Variants of fertilisation levels	*SOC, mg g^−1		C/N		DOC, mg g^−1		DOCp, %
	0–0.20 m	0.20–0.40 m	0–0.20 m	0.20–0.40 m	0–0.20 m	0.20–0.40 m	0–0.20 m	0.20–0.40 m
N0P0K0	20	13	11.8	11.4	0.15	0.12	0.75	0.80
N60P22K50	20	14	11.1	12.7	0.15	0.14	0.75	0.97
N90P22K50	19	15	11.2	12.6	0.15	0.13	0.79	0.87
N120P33K75	21	17	10.8	12.2	0.16	0.12	0.78	0.69
N60P22K50 + FYM30	23	15	11.8	12.5	0.16	0.13	0.70	0.86
N90P22K50 + FYM30	23	16	11.8	12.3	0.18	0.14	0.78	0.91
N120P33K75 + FYM30	23	14	11.5	11.3	0.16	0.12	0.68	0.76
N60P22K50 + FYM60	23	15	11.8	11.6	0.14	0.13	0.61	0.74
N90P22K50 + FYM60	27	18	13.3	12.5	0.19	0.15	0.70	1.07
N120P33K75 + FYM60	22	18	10.7	13.5	0.18	0.13	0.80	0.74
LSD 95%	1.6	1.2	0.53	0.47	0.011	0.007	0.064	0.084

* – SOC – total soil organic carbon; C/N – total soil organic carbon (C) / soil nitrogen (N); DOC – is water-dissolved soil organic carbon; DOCp = 100 × (DOC / SOC); LSD95% – level of 95% confidence in the LSD0.05 (LSD; least significant difference) test MS Excel