A new method to calculate soil loss tolerance for sustainable soil productivity in farmland

Abstract

Soil loss tolerance (T) is a widely used concept for assessing potential risks of soil erosion and is a criterion for assessing the effectiveness of soil and water conservation projects. However, current approaches for calculating T values lack a strong scientific basis, and few practicable methods are available. Many questions remain regarding which parameters, such as planning periods and offset damages, should be included in calculating T values. Here, we developed a new method to calculate soil loss tolerance as a function of the soil productivity index (SPI) for farmland. To achieve sustainable soil productivity in farmland, erosion rates leading to SPI values lower than the lower boundary of soil productivity (SPI0) are not tolerable and must be controlled by soil conservation measures. We applied this method in the Red River Basin of China based on the investigation of typical soil profiles and crop yields. Our results show that the T values in the Red River Basin ranged from 0.91 to 10.24 t ha −1 a −1. The SPI0 and the lowest limit of soil loss tolerance (T1) were 0.4 and 0.91 t ha −1 a −1 , respectively. Here, we demonstrate that, when determining T values in farmland, (1) the soil formation rate and offset damage should not be core items, (2) the "planning period" concept should be replaced by "sustainability", (3) the management objective of T should be the sustainability of the soil resource, and (4) the T values of farmland should be determined according to soil productivity. We provide a reasonable and feasible method to determine T for farmland, which will help maintain the sustainability of soil productivity.

Estimation of Soil Loss Tolerance in Olive Groves as an Indicator of Sustainability: The Case of the Estepa Region (Andalusia, Spain)

“…where ERF i is the erosion retardation factor of erosion level i (t ha −1 year −1 ); nERF i is the normalized erosion retardation factor of erosion level i (t ha −1 year −1 ); nERFmax is the maximum value of the normalized erosion retardation factor (t ha −1 year −1 ); nERFmin is the minimum value of the normalized erosion retardation factor (t ha −1 year −1 ). Fuentes Yagüe [54] and Duan et al [55] point out that the erosion retardation factor (ERF i ) will only be reliable for crops where soil variables present non-normalized values with gravels ranging from 0 to 40%, porosity between 30 to 90%, and a range of organic matter from 0 to 4%.…”

“…The Soil Productivity Index (SPI), postulated and modified by Duan et al [55][56][57], was calibrated and adapted for each treatment and erosion level of the olive groves of the PDO Estepa (Equation (11)). To estimate this index, it is necessary to consider the influence of the main variables closely linked to edaphic productivity: pH, organic matter, potassium, and clays.…”

“…These sufficiency values (dimensionless quantity normalized to 0-1) reflect the relative suitability of the index to crop growth: The higher the value, the more suitable for crop growth [57]. Sufficiency values were estimated from the empirical data obtained (see Table 3) according Duan et al [55,56].…”

“…where SPI i is the Soil Productivity Index of the erosion level i (dimensionless, value ranging from 0 to 1); SM i is the moisture sufficiency value of erosion level i; SpH i is the pH sufficiency value of erosion level i; SOM i is the organic matter sufficiency value of erosion level i; SK i is the potassium sufficiency value of erosion level i; SCli is the clay sufficiency value of erosion level i; W i is the weight of soil of erosion category i (t ha −1 year −1 ); E i is the erosion of erosion category i (t ha −1 year −1 ); R is the regeneration soil rate (t ha −1 year −1 ); t is the simulation time (years); Wmaximum is the maximum soil weight among all treatments (t ha −1 year −1 ). Finally, SPI values lower than 0.4 correspond to a low productivity, while SPI values between 0.4 to 0.8 indicate an average productivity and values higher than 0.8 correspond to high productivity [55]. Figure 3 summarizes the SLTI values considering bibliographic empirical soil parameters according to technical and institutional (i.e., official) data from Moreira-Madueño and BOJA [19,23,27], referring to the olive groves of Andalusia and represented by the different PDOs considered (see data in Table 1).…”

Infiltration and Soil Loss Changes during the Growing Season under Ploughing and Conservation Tillage

“…The highest soil loss value measured, due to the most extreme precipitation event, even under the seedbed condition, did not exceed the value of tolerable soil loss [51]. The single soil loss results owing to the simulated rainfalls are listed in Table 1.…”