Effects of soil crust and crop on runoff and erosion in Loess Plateau

Figures & data

Figure 1. Location of Yangling in the Loess Plateau.

Figure 2. Schematic of rainfall simulator (a) and runoff plots (b).

Table 1. Planting patterns and time of various crops.

Crops	Varieties	Planting spacing	Crop planting patterns and density	Planting time
Corn	Zhengdan958	25 cm × 60 cm	66667 plants per hm^2, hole sowing	20 June 2009
Soybean	Zhonghuang13	20 cm × 40 cm	125000 plants per hm^2, hole sowing	1 July 2010
Millet	Jingu29	10 cm × 20 cm	500000 plants per hm^2, sowing in drill	16 May 2010
Wheat	Xiaoyan22	20 cm (Row spacing)	Seedling quantity of 130 kg/hm^2, sowing in drill	30 September 2009

Note: Thinning out seedlings of millet in V3 stage, 10-cm plant spacing.

Figure 3. Variations of soil crust thickness (SCT) before and after the rain in corn (a), soybean (b), millet (c), and winter wheat (d) growth stage.

Note: SL, stubble field; BS, bare soil.

Figure 4. Variations of soil crust coverage (SCC) before and after the rain in corn (a), soybean (b), millet (c), and winter wheat (d) growth stage.

Note: SL, stubble field; BS, bare soil.

Table 2. Influences of soil crust on runoff and sediment yield in different growth stages of various crops.

			Crusts surface					No crusts surface
Crop	Observation date	LAI	Time producing runoff	Runoff rate (mm/h)	Runoff coefficient	Sediment yield (g/m^2·h)	Sediment concentration (g/L)	Time producing runoff	Runoff rate (mm/h)	Runoff coefficient	Sediment yield (g/m^2·h)	Sediment concentration (g/L)
Corn	11 July 2009	0.41	0 m 55 s	49.5	0.62	301.0	6.09	3 m 57 s	44.1	0.55	374.9	8.50
	21 July 2009	1.35	1 m 26 s	42.6	0.53	256.1	6.01	9 m 03 s	37.7	0.47	311.4	8.27
	31 July 2009	2.32	1 m 40 s	38.9	0.49	205.8	5.28	13 m 17 s	28.4	0.36	221.4	7.79
	11 August 2009	3.52	0 m 46 s	35.0	0.44	122.1	3.49	42 m 05 s	25.6	0.32	128.8	5.03
	21 August 2009	4.45	3 m 42 s	29.0	0.36	108.5	3.74	28 m 26 s	20.1	0.25	114.9	5.71
	10 September 2009	SL	1 m 41 s	45.3	0.57	284.2	6.27	16 m 36 s	36.7	0.46	324.1	8.83
Soybean	6 July 2010	0.61	1 m 21 s	51.8	0.65	314.2	5.54	2 m 02 s	45.0	0.56	361.5	7.63
	15 July 2010	1.99	2 m 02 s	40.5	0.51	243.1	5.32	2 m 49 s	37.6	0.47	292.6	7.50
	22 July 2010	3.82	0 m 43 s	33.3	0.42	149.2	4.27	10 m 54 s	26.6	0.33	172.7	5.75
	2 August 2010	4.83	1 m 25 s	30.9	0.39	113.0	3.56	3 m 00 s	23.3	0.29	126.0	5.34
	18 August 2010	6.59	1 m 25 s	28.1	0.35	97.3	3.17	3 m 54 s	19.7	0.25	105.8	5.20
Millet	25 May 2010	0.35	1 m 32 s	52.2	0.65	321.8	5.49	1 m 27 s	45.0	0.56	375.6	7.94
	2 June 2010	0.99	1 m 39 s	47.2	0.59	272.6	5.14	3 m 54 s	40.1	0.50	331.8	8.50
	16 June 2010	2.43	0 m 27 s	41.9	0.52	102.1	2.30	10 m 22 s	32.9	0.41	115.8	3.39
	23 June 2010	3.08	1 m 44 s	34.9	0.44	73.8	1.98	3 m 14 s	25.7	0.32	76.8	2.84
	29 June 2010	3.56	1 m 33 s	30.1	0.38	66.8	2.12	3 m 29 s	20.7	0.26	69.3	3.23
Winter wheat	24 March 2010	3.35	3 m 25 s	4.7	0.06	3.5	0.69	6 m 55 s	4.2	0.05	3.6	1.62
	7 April 2010	4.42	2 m 35 s	4.3	0.05	3.0	0.70	7 m 48 s	3.7	0.05	3.2	0.95
	20 April 2010	5.27	22 m 04 s	2.2	0.03	1.5	0.65	23 m 20 s	1.5	0.02	1.6	1.15
	27 April 2010	5.80	25 m 04 s	1.9	0.02	1.1	0.57	26 m 20 s	1.3	0.02	1.2	1.05
	14 May 2010	SL	9 m 36 s	3.9	0.05	2.9	0.73	12 m 25 s	3.4	0.04	3.4	1.22
BS (Average)			1 m 03 s	52.4	0.66	399.9	7.63	3 m 34 s	49.9	0.62	510.5	10.23

Note: LAI, leaf area; SL, stubble land; BS, bare soil; m, minute; s, second.

Figure 5. Effect of soil crust on runoff formation processes on the slopes of corn (a), soybean (b), millet (c), winter wheat (d), and BS (e).

Note: Take an individual crop growth stage as an example, 4.45 of LAI with corn, 6.59 of LAI with soybean, 3.56 of LAI with millet, and 5.80 of LAI with winter wheat. Take an individual bare slope as an example at the same stage of corn. Same growth stages in Figure 6 and Figure 7. BS-Crust cover, bare soil with soil crust; BS-No crust, bare soil without soil crust; Crop-Crust cover, crop land with soil crust; Crop-No crust, crop land without soil crust.

Figure 6. Effect of soil crust on sediment yield formation processes on the slopes of corn (a), soybean (b), millet (c), winter wheat (d), and BC (e).

Note: Take an individual crop growth stage and BC as an example, growth stages are the same to those in Figure 5. BS-Crust cover, bare soil with soil crust; BS-No crust, bare soil without soil crust; Crop-Crust cover, crop land with soil crust; Crop-No crust, crop land without soil crust.

Figure 7. Effect of soil crust on change process of sediment concentration on the slopes of corn (a), soybean (b), millet (c), winter wheat (d), and BC (e).

Note: Take an individual crop growth stage and bare soil as an example, growth stages are the same to those in Figure 5. BS-Crust cover, bare soil with soil crust; BS-No crust, bare soil without soil crust; Crop-Crust cover, crop land with soil crust; Crop-No crust, crop land without soil crust.