Rainfall and land management effects on erosion and soil properties in traditional Brazilian tobacco plantations

Figures & data

Figure 1. Geographical location of the study area within the municipality of Ivaí (Paraná, Brazil).

Figure 2. Technical characteristics of the installation of the Gerlach troughs: (a) planting, (b) harvesting, and (c) manual raingauge.

Table 1. Agricultural calendar for the farming activities. NT: no-tillage; CT: conventional tillage. Month in the form mm/yy.

Month	Crop	Agricultural activity
09/14	NT tobacco	Desiccation of oats (dead layer). Tobacco was planted under oat straw (planting activities).
10/14		Weeding using herbicides. Soil was not stirred (covered soil).
11/14
12/14		Weekly collection of leaves and transport by mules to the farm warehouse.
01/15
02/15
03/15	Black bean	Soil grading with tobacco crop residues. Black beans were planted.
04/15		Weeding using herbicides. Soil was not stirred.
05/15
06/15		Black beans harvesting. Soil was turned using mules.
07/15	Black oats	Soil was turned using mules. Oats were planted (exposed soil).
08/15		Weeding using herbicides. Soil was not stirred.
09/15	CT tobacco	Oats was removed. Furrows were built. Tobacco was planted (exposed soil).
10/15		Soil was turned in the furrows using mules.
11/15		Use of a hoe for weeding in the inter-row areas.
12/15		Beginning of weekly collection of leaves and transport by mules to the farm warehouse.
01/16
02/16	CT tobacco	End of weekly collection of leaves and transport by mules to the farm warehouse.

Figure 3. Box plots of runoff coefficient per crop type during the studied period. The graphs above each box plot show the amount of rain that fell during each rainfall event.

Figure 4. Box plots of soil loss rates per crop type during the studied period. The graphs above each box plot show the amount of rain that fell during each rainfall event.

Figure 5. Scatter plots of rainfall (x-axis) and soil loss rates (y-axis) for different crops.

Figure 6. Scatter plots of bare soil percentage (x-axis) and soil loss rates (y-axis) for different crops.

Table 2. Evolution of some soil properties during the study. OM: organic matter; BD: bulk density; NT: no-tillage; CT: conventional tillage.

		NT				Bean				Oats				CT
	Soil depth (cm)	0–5^1	0–5^2	5–10^1	5–10^2	0–5^1	0–5^2	5–10^1	5–10^2	0–5^1	0–5^2	5–10^1	5–10^2	0–5^1	0–5^2	5–10^1	5–10^2
OM (g kg^−1)		25.2	34.3	21.7	35.4	26.9	28.3	28.5	28.2	29.0	32.2	28.2	32.0	19.7	20.9	23.2	31.5
		±2.7	±4.5	±3.2	±2.9	±3.6	±2.8	±2.3	±1.8	±2.3	±2.1	±3.0	±2.2	±1.3	±2.2	±2.8	±2.7
	Max	29.0	39.4	25.4	39.0	31.0	30.1	32.1	30.4	31.5	34.8	31.4	34.8	21.8	23.1	26.9	34.7
	Min	23.1	27.8	17.9	32.4	21.7	23.4	25.7	26.1	26.4	29.7	23.7	29.3	18.7	17.9	20.7	26.9
BD (g cm^−3)		1.07	1.21	1.08	1.18	1.02	1.09	1.05	1.16	1.00	1.05	1.01	1.16	1.01	1.22	1.02	1.20
		±0.05	±0.02	±0.02	±0.03	±0.03	±0.03	±0.05	±0.04	±0.06	±0.02	±0.05	0.04	±0.03	±0.02	±0.06	±0.04
	Max	1.12	1.24	1.10	1.21	1.06	1.14	1.09	1.21	1.07	1.07	1.08	1.21	1.03	1.24	1.08	1.24
	Min	0.99	1.18	1.06	1.13	0.98	1.05	0.97	1.11	0.94	1.01	0.94	1.11	0.97	1.19	0.96	1.14
pH		6.2	5.5	6.4	5.8	6.5	6.3	6.2	6.3	6.3	6.2	6.3	6.0	6.0	6.1	6.0	5.7
		±0.2	±0.3	±0.2	±0.1	±0.3	±0.3	±0.3	±0.2	±0.2	±0.2	±0.4	±0.3	±0.3	±0.3	±0.2	±0.3
	Max	6.3	5.9	6.7	5.9	6.9	6.6	6.7	6.7	6.7	6.4	6.8	6.4	6.4	6.4	6.3	6.1
	Min	5.9	5.2	6.2	5.7	6.2	5.9	5.8	6.1	6.1	5.9	5.7	5.5	5.7	5.7	5.8	5.3

¹Soil properties at the beginning of the crop season; ²soil properties at the end of the crop season.

Table 3. Analysis of the statistical differences between soil properties. Bold indicates statistical differences were found. NT: no-tillage; CT: conventional tillage; OM: organic matter; BD: bulk density.

	NT		Bean		Oats		CT
	0–5	5–10	0–5	5–10	0–5	5–10	0–5	5–10
OM	p < 0.005*	p < 0.001*	p < 0.512	p < 0.782	p < 0.053	p < 0.029*	p < 0.349	p < 0.001*
BD	p < 0.001*	p < 0.001*	p < 0.012*	p < 0.003*	p < 0.135	p < 0.001*	p < 0.001*	p < 0.001
pH	p < 0.002*	p < 0.001*	p < 0.296	p < 0.596	p < 0.578	p < 0.288	p < 0.84	p < 0.082

*Normality test failed and Holm-Sidak test was conducted.