Values of the Coverage and the Configuration Coefficients with the Crop-growths

Study on the applicability of a soil loss equation (I)

Abstract

To estimate the amount of soil eroded from the farmland due to rainfall is very important in agriculture. The present study is aimed at investigating the applicability of an equation (q_e =aK_eL_dα sinβθ q_rγ) to predict soil loss (q_e) directly from rainfall (q_r) by comparing the calculated values of soil losses with the observed soil losses and from the comparison, to determine the values of two unknown coefficients (a_c, b) which lie in the expanded forms of the equation. For this study, planting different types of crops in a free type test field, soil losses and surface runoffs were recorded after every rainfall at different growth-stages of the crops.
Under the analytical outputs of 2 year-long observations, the values of the coefficients (a_c, b) or the individual b, determined from the point of the rate of applicability of the calculated soil losses with respect to the observed soil losses in each crop are as follows:
Meadows: b=1.1-1.6, Carrot: b=1.5, Soybean:(a_c, b) = (0.9, 1.1), Corn:(a_c, b) = (0.9, 1.0), Radish:(a_c, b) = (0.8, 2.0), Komatsuna:(a_c, b) = (0.2-0.3, 1.9-2.0), Red clover:(a_c, b) = (1.0, 1.8).
From the determined values of the coefficients (a_c, b) or the individual b for each cultivated crop, it is found that in cases of the crops where the vertical distance from the ground surface to the mid-point of the leaf area is negligible (such as, meadows, carrot etc.), making no relation with the value of a_c, the only b value needs to assume to calculate the soil loss. On the other hand, in cases of the other crops with their bigger aerial parts (in the present study, soybean, corn, radish, komatsuna and red clover), from their values of (a_c, b), it has also been concluded that the cover rate and the space ratio of vegetation strongly influence the erosion coefficient and thus the soil loss.
Finally, considering the determined (a_c, b) or the only b values of each cultivated crop as the representative values for some categories of field crops having the similar characteristics, the crops have been classified into four groups, namely, i) Vegetables (Root and Leaf); ii) Grasses; iii) Beans and iv) Cereals with their respective (a_c, b) or b values.