Runoff and sediment reduction benefits of soil and water conservation and its mechanism of corn stalk juice

Abstract: Soil and water loss has been degrading the precious soil and water resources. How to control soil and water loss has been paid increasingly great attentions by the societies and scientists all over the world. Chinese Loess Plateau is the region where water and soil loss is the most serious in the world. Therefore, Chinese people have got a long history of soil and water conservation practices and invented many sound measures for soil and water conservation, such as biological methods, tillage measures, engineering technologies and small watershed comprehensive management. However, the serious erosion problems have not been significantly improved in the Loess Plateau because of large investment, long controlled cycle, slow effect and other issues of these measures. In recent, manufactured and natural soil amendments such as polyacrylamide, biological crust, corn stalk juice have been effective in runoff control and sediment reduction, and especially corn stalk juice is natural byproduct and belongs to natural soil amendment. Corn stalk juice was tested for its effects on runoff generation intensity and sediment yield rate in the previous literature. In this paper, corn stalk juice was tested for its effects on runoff and sediment reduction benefit and soil properties. The experimental design involved the simulated rainfall intensity (50 mm/h), 2 application concentrations of diluted corn stalk juice (25% and 50%), and the application amount of diluted corn stalk juice (1 000 mL) on 2 soil boxes which were 1.2 m long, 0.8 m wide, and 0.4 m deep and set to 15% slope. Rainfall experiments were conducted at the Institute of Soil and Water Conservation, Gansu Province, China. Surface soil (0 20 cm) materials were from Doujia Mountain Experimental Station in Lanzhou City, Gansu Province, and they had 72% clay, 10% silt and 18% sand. The test soil was air-dried, crushed and then passed through a 10 mm sieve. The corn stalk juice used in this study was extracted from field corn plants grown at Yuzhong Campus of Lanzhou University. A 60-min continuous rainstorm was applied. The rainstorm intensity was 50 mm/h. Runoff samples were collected in 10 L HDPE (high density polyethylene) bucket every 5 min during the whole rainfall process. Time of filling the runoff bucket was recorded. After each run, the sample buckets were weighed immediately to obtain the runoff rate. After settling overnight, the excess water was poured off the buckets. The sediments were transferred to the iron boxes and placed in the oven at 105°C for at least 24 h or until the sediments were dried. Dry weights were then taken to calculate the sediment delivery rate and sediment concentration. Mean weight diameter (MWD) of soil aggregate, and soil organic matter mass fraction under application concentration of different corn stalk juice were measured by the traditional measure method in the laboratory. The results showed that all kinds of diluted corn stalk juice application could increase the soil aggregate MWD and soil organic matter mass fraction, but reduce runoff generation intensity and sediment yield rate. When application concentration of corn stalk juice was 0%, 25% and 50%, the corresponding soil aggregates MWD was 0.18, 0.46 and 0.51 mm, respectively, and the corresponding soil organic matter mass fraction was 5.70%, 6.75% and 7.17%, respectively. When application concentration of diluted corn stalk juice was 25% and 50%, the corresponding runoff reduction benefit was 45.81% and 48.34%, respectively, and the corresponding sediment reduction benefit was 65.00% and 75.47%, respectively. Sediment reduction benefit was greater than runoff benefit reduction under the same application concentration of diluted corn stalk juice. Runoff and sediment reduction benefit reduced with the increasing of time. The average annual runoff reduction benefit was about 12.5%, and the average annual sediment reduction benefit was about 14.1%. The optimum application amount of corn stalk juice and the optimum volume ratio of corn stalk juice to running water were suggested to be 1 041.7 mL/m2 and 1:1, respectively.