Release of nitrogen, phosphorus, and potassium during the decomposition of apple (Malus domestica) leaf litter under different fertilization regimes in Loess Plateau, China

Figures & data

Figure 1. Changes in mass during 24-month incubation for three different litters sampled from trees: control, unfertilized (CK), which received low rate fertilizer (LF), and high rate fertilizer (HF). Values are means (n = 3) and bars are standard errors.

Table 1. Initial concentrations of nitrogen, phosphorus and potassium (in g kg^–1) of the apple leaf litters

Little type	Nitrogen	Phosphorus	Potassium
CK	11.6 ± 0.6b	1.10 ± 0.28b	7.90 ± 0.07b
LF	12.5 ± 0.5b	1.17 ± 0.07b	8.00 ± 0.05ab
HF	14.6 ± 1.1a	1.31 ± 0.06a	8.32 ± 0.14a
Data are shown as percent on dry weight basis and represent mean ± standard deviations, n = 3. CK, LF and HF represent litter from unfertilized (control), fertilized at low rate and fertilized at high rate, respectively.
Values in the same column with different letters are statistically different (P < 0.05).

Figure 2. Changes in concentrations of (a) nitrogen (N), (b) phosphorus (P), and (c) potassium (K) during 24-month incubation for three different litters sampled from trees: control, unfertilized (CK), which received low rate fertilizer (LF), and high rate fertilizer (HF). Values are means (n = 3) and bars are standard errors.

Table 2. Estimated decay rates of different types of litter mass for 6, 12 and 24 months after start of the experiment

Litter type	Decomposition rate, K (month^−1)
	6 months	R ^2	12 months	R ^2	24 months	R ^2
CK	0.032 (0.006)b	0.96	0.058 (0.007)a	0.97	0.051 (0.004)a	0.97
LF	0.039 (0.004)a	0.91	0.060 (0.004)a	0.96	0.050 (0.003)a	0.97
HF	0.043 (0.005)a	0.98	0.062 (0.005)a	0.95	0.051 (0.003)a	0.96
CK, LF and HF represent litter from apple trees that are unfertilized (control), fertilized at low rate, and fertilized at high rate, respectively; K is the decay constant; R ^2 is the coefficient of determination.
Values followed by different letters in each column are statistically different (P < 0.05).

Figure 3. Changes in amounts of (a) nitrogen (N), (b) phosphorus (P), and (c) potassium (K) remaining during 24-month incubation for three different litters sampled from trees: control, unfertilized (CK), which received low rate fertilizer (LF), and high rate fertilizer (HF). Values are means (n = 3) and bars are standard errors.

Table 3. Estimate of nitrogen (N), phosphorus (P), potassium (K) release of different litters of apple trees under three different fertilizer regimes after 12 and 24 months of decomposition

			RAN (g bag^−1)		RRN (g kg^−1)		REAN (kg ha^−1)		PRF (%)
Treatment		IAN (g bag^−1)	12 months	24 months	12 months	24 months	12 months	24 months	12 months	24 months
N	CK	0.292	0.278	0.152	0.554	5.550	1.46b	14.62c	–	–
	LF	0.315	0.293	0.151	0.871	6.483	3.08ab	22.92b	10.26	38.20
	HF	0.367	0.330	0.148	1.488	8.748	7.32a	43.05a	10.46	30.80
P	CK	0.028	0.017	0.006	0.434	0.852	1.14b	2.25b	–	–
	LF	0.029	0.017	0.007	0.483	0.911	1.71ab	3.22ab	11.38	10.73
	HF	0.033	0.018	0.007	0.591	1.034	2.91a	5.09a	8.32	7.27
K	CK	0.199	0.028	0.016	6.790	7.285	17.88c	19.19c	–	–
	LF	0.201	0.027	0.016	6.919	7.371	24.45b	26.05b	81.52	43.42
	HF	0.209	0.025	0.015	7.326	7.712	36.05a	43.82a	51.51	31.30
CK, LF and HF represent litter from apple trees which were unfertilized (control), fertilized at low rate and fertilized at high rate, respectively; IAN is the initial amount of nutrient; RAN is the remaining amount of nutrient at the end of 12- and 24-month incubation; RRN is the return rate of nutrient; REAN is the return amount of nutrient at the end of 12- and 24-months; PRF is the proportion of return rate to fertilizer.
Values followed by different letters in each column are statistically different (P < 0.05).