Land use change from paddy rice to sugarcane under long-term no-till conditions: increase P balance, soil organic matter and sugarcane productivity

Figures & data

Figure 1. % Sand (a), % silt (b), % clay (c) and bulk density (d) after LUC in soil profile (1 m). Horizontal bars represent standard error of the mean (SEM), and different lowercase letters indicate statistically significant differences between the land-use types for the specific depth; capital letters indicate statistically significant differences between the soil layers for the same land-use types (p < 0.05). PRC: monocrop paddy rice, SC6: it was converted from paddy rice to sugarcane for 6 years, SC13: it was converted from paddy rice to sugarcane for 13 years, and SC17: it was converted from paddy rice to sugarcane for 17 years.

Figure 2. Cation exchange capacity (CEC_pH7) (a), soil pH (pH_1:1H2O) (b), organic matter (SOM) (c) and available phosphorus (p_av) (d) after LUC in soil profile (1 m). horizontal bars represent standard error of the mean (SEM), and different lowercase letters indicate statistically significant differences between the land-use types for the specific depth; capital letters indicate statistically significant differences between the soil layers for the same land-use types (p < 0.05). LUC: land use change, PRC: monocrop paddy rice, SC6: it was converted from paddy rice to sugarcane for 6 years, SC13: it was converted from paddy rice to sugarcane for 13 years, and SC17: it was converted from paddy rice to sugarcane for 17 years.

Table 1. Significance of single and interacted factors influencing the soil physicochemical properties.

	LUC	SD	LUC*SD
% sand	**	**	ns
% silt	ns	**	ns
% clay	*	**	ns
Bulk density	**	**	*
CECpH7	**	**	ns
pH1:1 H2O	ns	**	ns
SOM	**	**	**
Pav	**	**	**
Kex	**	**	**
Caex	**	**	**
NH4^+-N	**	**	**
NO3^− -N	**	**	**
Total mineral N	**	**	**
Total N	**	**	**

Notes: **Significantly different at p < 0.01, *significantly different at p < 0.05, and ns: not significantly different. LUC: land use change, SD: soil depth, CEC_pH7: cation exchange capacity, SOM: soil organic matter, Pav: available phosphorus, K_ex: exchangeable K, Ca_ex: exchangeable Ca, NH₄⁺-N: soil NH₄⁺-N, NO₃⁻ -N: soil NO₃^{` -}N, Total mineral N: total mineral nitrogen, Total N: total nitrogen.

Figure 3. Exchangeable K (K_ex) (a), exchangeable Ca (Ca_ex) (b), total N (Total N) (c), soil NH₄⁺-N (NH₄⁺-N) (d), soil NO₃⁻N (NO₃⁻ -N) (e) and total mineral nitrogen (Total mineral N) (f) after LUC in soil profile (1 m). Horizontal bars represent Standard Error of the Mean (SEM), and different lowercase letters indicate statistically significant differences between the land-use types for the specific depth; capital letters indicate statistically significant differences between the soil layers for the same land-use types (p < 0.05). LUC: land use change, PRC: monocrop paddy rice, SC6: it was converted from paddy rice to sugarcane for 6 years, SC13: it was converted from paddy rice to sugarcane for 13 years, and SC17: it was converted from paddy rice to sugarcane for 17 years.

Figure 4. Annual apparent nitrogen (a), phosphorus (b) and potassium (c) balances in different land use (kg ha⁻¹) and N, P, K uptakes (d) of crop at final harvest. Vertical bars represent Standard Error of the Mean (SEM), and different lower-case letters indicate statistically significant differences (p < 0.05). LUC: land use change, PRC: monocrop paddy rice, SC6: it was converted from paddy rice to sugarcane for 6 years, SC13: it was converted from paddy rice to sugarcane for 13 years, and SC17: it was converted from paddy rice to sugarcane for 17 years.

Figure 5. Internal Nutrient use efficiency (IE_N,P,K):[yield/total N, P, K uptake] (a), and Partial factor productivity of applied Nutrient (PFP_N,P,K): [yield/Nutrient applied] (b) of crop at final harvest. Vertical bars represent standard error of the mean (SEM), and different lower-case letters indicate statistically significant differences (p < 0.05). LUC: land use change, PRC: monocrop paddy rice, SC6: it was converted from paddy rice to sugarcane for 6 years, SC13: it was converted from paddy rice to sugarcane for 13 years, and SC17: it was converted from paddy rice to sugarcane for 17 years.

Table 2. Cane populations and plant height of sugarcane at 4, 6, 8, 10 and 12 months after harvesting (MAH).

LUC	Cane populations (Number of stalks ha^−1)
	4 MAH		6 MAH		8 MAH			10 MAH		12 MAH
SC6	81,597±4437	b	75,232±4551	b	65,972±2933	c	63,426±1022		b	63,542±1075	b
SC13	91,528±4883	b	88,681±1725	a	84,722±928	b	79,167±2310		a	77,986±2310	a
SC17	108,333±9220	a	105,295±8635	a	99,913±928	a	89,410±5100		a	86,632± 5100	a
F-test	*		*		**			**		*
Plant height (cm)
SC6	114.33±10.42		208.29±15.59		252.71±15.70			278.42±19.01		283.92±20.44
SC13	97.67±6.71		176.17±15.34		231.77±20.30			278.79±16.17		282.63±16.43
SC17	102.67±5.05		192.50±8.73		243.79±14.22			277.63±19.78		282.42±18.23
F-test	ns		ns		ns			ns		ns

Notes: The results are mean (n = 4) ± standard error of the mean (SEM). Means followed by the same letter(s) among sites are not significantly different (p > 0.05). **Significantly different at p < 0.01, *significantly different at p < 0.05 and ns: not significantly different. LUC: land use change, PRC: monocrop paddy rice, SC6: it was converted from paddy rice to sugarcane for 6 years, SC13: it was converted from paddy rice to sugarcane for 13 years, and SC17: it was converted from paddy rice to sugarcane for 17 years.

Table 3. Single stalk weight, millable cane, leaf weight, °Brix, commercial cane sugar (CCS), and dry weight of sugarcane at final harvest.

LUC	Single stalk weight (kg)				Millable cane yield (Mg ha^−1)		Leaf weight (Mg ha^−1)		°Brix		CCS
SC6	1.42 ± 0.03		a		88.75 ± 2.30	b	20.22 ± 0.53		22.09 ± 0.62		13.18 ± 0.41
SC13	1.22 ± 0.01		b		93.78 ± 3.17	ab	21.75 ± 1.38		22.69 ± 0.46		13.66 ± 0.26
SC17	1.18 ± 0.04		b		100.24 ± 1.64	a	23.90 ± 0.90		23.40 ± 0.39		12.47 ± 1.18
F-test	**				*		ns		ns		ns
	Dry weight (Mg ha^−1)
LUC		Yield				Straw			Total
SC6		23.00 ± 0.66		c		10.26 ± 0.32			33.26 ± 0.86	c
SC13		28.40 ± 0.89		b		11.60 ± 0.36			40.01 ± 1.13	b
SC17		33.51 ± 1.23		a		12.19 ± 0.46			45.71 ± 1.59	a
F-test		**				ns			**

Notes: The results are mean (n = 4) ± standard error of the mean (SEM). Means followed by the same letter(s) among sites are not significantly different (p > 0.05). **Significantly different at p < 0.01, *significantly different at p < 0.05 and ns: not significantly different. LUC: land use change, SC6: it was converted from paddy rice to sugarcane for 6 years, SC13: it was converted from paddy rice to sugarcane for 13 years, and SC17: it was converted from paddy rice to sugarcane for 17 years.

Figure 6. A conceptual diagram illustrating the impact of land use change from tilled paddy rice to long-term no-till sugarcane cropping, with consecutive returns of sugarcane straw, on various soil physicochemical properties, nutrient balance, yield and nutrient use efficiency of sugarcane.

Data availability statement

The data are available upon request from the authors.