Nitrate leaching in granitic regosol as affected by N uptake and transpiration by corn

Figures & data

Table 1 Chemical characteristics of the soil before fertilizer application in the field experiment (2005)

	pH		C	N	Inorganic N (mg N kg^−1)		Olsen-P (mg P kg^−1)
	H2O	KCI	Total (g kg^−1)		NH4-N	NO3-N
CF-NP	77	6.0	2.5	0.3	1.9	0.0	24.8
CF-CPD	6.8	6.3	5.0	0.5	1.8	5.5	46.8
CF-HPD	7.9	5.6	2.7	0.3	2.4	0.0	26.1
Values are means (n = 3). CF-NP, chemical fertilizer-no planting; CF-CPD, chemical fertilizer-conventional planting density; CF-HPD, chemical fertilizer-high planting density.

Figure 1  Cumulative nitrate–nitrogen (NO3-N) leaching and shoot dry matter in the chemical fertilizer-conventional planting density treatment in the field experiment from May 2003 to September 2005.

Figure 2  (A) Precipitation and (B) cumulative drainage volume from the capillary lysimeter in the field experiment (2005). CF-NP, chemical fertilizer-no planting; CF-CPD, chemical fertilizer-conventional planting density; CF-HPD, chemical fertilizer-high planting density. Error bars represent standard deviation.

Figure 3  Effect of planting density on (A) nitrate–nitrogen (NO3-N) concentration in the drainage water and (B) cumulative NO3-N leaching from the capillary lysimeter in the field experiment (2005). CF-NP, chemical fertilizer-no planting; CF-CPD, chemical fertilizer-conventional planting density; CF-HPD, chemical fertilizer-high planting density. Error bars represent standard deviation.

Figure 4  Effect of planting density on inorganic N in the surface soil (0–10 cm) in the field experiment (2005). CF-NP, chemical fertilizer-no planting; CF-CPD, chemical fertilizer-conventional planting density; CF-HPD, chemical fertilizer-high planting density. Error bars represent standard deviation.

Table 2 Shoot dry matter and shoot N uptake by corn in the field experiment (2005)

		15 DAT	30 DAT	49 DAT	60 DAT	90 DAT
Soot dry matter (Mg ha^−1)	CF-CPD	0.02 ± 0.0	0.4 ± 0.1	3.5 ± 0.2	5.7 ± 0.5	14.4 ± 0.8
	CF-HPD	0.04 ± 0.0	1.2 ± 0.3	5.9 ± 0.4	9.1 ± 1.4	20.7 ± 2.9
Shoot N uptake (kg N ha^−1)	CF-CPD	0.9 ± 0.2	12.3 ± 1.4	54.6 ± 0.4	59.9 ± 6.3	111.6 ± 7.6
	CF-HPD	1.6 ± 0.3	40.4 ± 9.4	103.2 ± 16.6	97.8 ± 2.1	130.7 ± 21.8
Values are means ± standard deviation (n = 3). CF-CPD, chemical fertilizer-conventional planting density; CF-HPD, chemical fertilizer-high planting density; DAT, days after treatment.

Table 3 Microbial biomass N in the field experiment (2005)

		0 DAT	15 DAT	30 DAT	60 DAT	90 DAT
Microbial biomass	CF-CPD	15.2 ± 1.8	19.9 ± 1.0	22.1 ± 0.3	30.2 ± 4.4	27.9 ± 1.4
N (kg N ha^−1)	CF-NP	15.2 ± 1.8	14.1 ± 2.7	15.4 ± 1.7	16.3 ± 2.6	22.2 ± 1.3
Values are means ± standard deviation (n = 3). CF-CPD, chemical fertilizer-conventional planting density; CF-HPD, chemical fertilizer-high planting density; DAT, days after treatment.

Figure 5  Effect of planting density on nitrate–nitrogen (NO3-N) leaching in the soil column experiment. NP, no plant; 1-plant, one plant per soil column; 2-plant, two plants per soil column; 4-plant, four plants per soil column. Error bars represent standard deviation.

Figure 6  Effect of planting density on (A) cumulative drainage volume and (B) cumulative evapotranspiration in the soil column experiment. NP, no plant; 1-plant, one plant per soil column; 2-plant, two plants per soil column; 4-plant, four plants per soil column. Error bars represent standard deviation.

Figure 7  Effect of planting density on nitrate–nitrogen (NO3-N) concentration in the drainage water in the soil column experiment. NP, no plant; 1-plant, one plant per soil column; 2-plant, two plants per soil column; 4-plant, four plants per soil column. Error bars represent standard deviation.

Table 4 Dry matter and N uptake at the beginning and the end of the water application period in the soil column experiment

	Dry matter (Mg ha^−1)				N uptake (kg N ha^−1)
	Shoot		Root		Shoot		Root
	Beginning	End	Beginning	End	Beginning	End	Beginning	End
1-plant	0.1 ± 0.0	0.8 ± 0.1	0.0 ± 0.0	0.4 ± 0.1	2.2 ± 0.3^†	9.7 ± 0.5	n.d.	2.9 ± 0.5
2-plant	0.2 ± 0.0	1.8 ± 0.3	0.1 ± 0.0	0.9 ± 0.1	6.0 ± 0.3^†	17.0 ± 2.2	n.d.	6.6 ± 0.2
4-plant	0.5 ± 0.0	2.8 ± 0.1	0.2 ± 0.0	1.4 ± 0.0	20.8 ± 2.6	25.1 ± 2.4	4.1 ± 0.6	9.6 ± 0.3
Values are means ± standard deviation (n = 3). ^†Values including root N uptake. n.d., not determined.

Figure 8  Cumulative nitrate–nitrogen (NO3-N) leaching, whole plant N uptake and retained N in the soil in the (A) chemical fertilizer-no planting, (B) chemical fertilizer-conventional planting density and (C) chemical fertilizer-high planting density treatments in the field experiment (2005).

Figure 9  Relationship between cumulative nitrate–nitrogen (NO3-N) leaching and shoot N uptake in the field experiment during the rainy season from 2003 to 2005. The data were from measurements taken 49 days after treatment (DAT) in each year. **P < 0.01.

Figure 10  Effect of planting density on cumulative nitrate–nitrogen (NO3-N) leaching, plant N uptake and the amount of retained NO3-N in the soil at the end of water application in the soil column experiment. Error bars represent standard deviation.

Figure 11  Relationship between the amount of retained nitrate–nitrogen (NO3-N) in the soil at the end of water application and cumulative transpiration by corn for 10 days of water application in the soil column experiment. **P < 0.01.