Land Degradation and Soil Conservation Measures in the Moldavian Plateau, Eastern Romania: A Case Study from the Racova Catchment

Land degradation by soil erosion, gullying and landslides and reservoir sedimentation is a major environmental threat in the Moldavian Plateau of eastern Romania. The widespread development of these processes in the last two centuries was favored mainly by traditional agriculture focused on ‘up-and-down slope’ farming on small plots. However, soil conservation measures were actively undertaken between 1970 and 1989. More recent legislation (No. 18/1991 Agricultural Real Estate Act) includes two provisions that discourage maintaining and extending soil conservation practices. Hence, the former contour farming system has been abandoned in favor of the traditional, inadequate farming methods. Thus, this paper reviews the impact of land degradation and soil conservation measures in a representative 32,908 ha catchment located in the Central Moldavian Plateau. Based on field measurements, the results show that the estimated mean long-term (1973–2017) sedimentation rate reaches 4.7 cm y−1 in the Puscasi Reservoir at the catchment outlet, resulting in an associated sediment delivery ratio of 0.28. The initial area of the Puscasi Reservoir at normal retention level has decreased by 32% and the water storage capacity has decreased by 39%. Consequently, land degradation remains a serious problem in the study area and effective soil conservation is urgently needed.

Using WaTEM/SEDEM to Configure Catchment Soil Conservation Measures for the Black Soil Region, Northeastern China

In recent years, to combat soil erosion, large-scale soil conservation measures have been implemented in the world. Evaluation of the integrated catchment management is urgently required. In the present study, soil erosion and sediment yield under 24 scenarios were predicted, based on the water and tillage erosion model and sediment delivery deposition model (WaTEM/SEDEM). The current catchment management was not ideal, with a catchment soil loss rate (SLR) of 599.88 t km−2 yr−1 and a sediment yield of 240.00 t km−2 yr−1. The catchment management with contour tillage on <3° slopes, hedgerow planting on 3–5° slopes, terracing on 5–8° slopes, and forestation on >8° slopes with trenches along the forest and dams in gullies was the best catchment management to control soil loss, with catchment SLR that was less than the tolerable value of 200 t km−2 yr−1. However, the SLR on the <3° slopes was still higher than the tolerable value. It is not enough to control soil loss by only implementing contour tillage measure on <3° slopes, and other measures should be further implemented on these slopes. In gullies, more measures should be implemented to prevent sediment flowing out of the catchments, in Northeastern China.

Responses of Runoff and Soil Loss on Slopes to Land Use Management and Rainfall Characteristics in Northern China

Soil conservation measures are widely used to control soil erosion and sediment loss; however, their proper usage relies on a deep understanding of the responses of runoff and sediment loss to land management and rainfall characteristics. In the present study, a long-term (2014–2020) monitored dataset derived from ten runoff plots in the upstream catchment of the Miyun Reservoir in Beijing, China, was used to study runoff and sediment loss responses to land use management and rainfall characteristics. The study results show that plots with no soil conservation measures had the highest runoff depth of 75 mm and suffered the highest sediment loss, at a rate of 3200 t km−2 yr−1. The terraced and vegetated plots generated lower runoff depths, with soil loss rates less than 213.0 t km−2 yr−1. With the exception of the contour tillage plots on steep slopes, the vegetation and engineering measures can efficiently reduce runoff and sediment loss, with both runoff and sediment reduction efficiencies higher than 76%. Statistical analyses indicate that, on the plots of bare soil and cultivation without soil conservation measures, runoff and sediment loss were mainly affected by the maximum 30 min rainfall intensity. However, on the plots with soil conservation measures, they were mainly determined by rainfall amount and duration. The sediment loss rate can be well fitted with the runoff depth using a power function. Based on the analyses, water-saving soil conservation measures are recommended for the study area. In addition, the size of terraces should be reconsidered on gentle slopes, and the coverage of forest, shrubs, and grass on slopes should be reduced, thus allowing for more surface runoff generation to ensure drinking water safety. In general, for the study area, soil conservation measures are required on the bare soil and cultivated slopes.

The Effect of Soil Conservation Measures on Runoff, Soil Erosion, TN, and TP Losses Based on Experimental Runoff Plots in Northern China

Total nitrogen (TN) and total phosphorous (TP) are the main pollutants affecting the water quality of the Miyun Reservoir, Beijing. However, few studies have been conducted on their responses to implemented soil conservation measures at a slope scale in northern China. To explore the impact of soil conservation measures on TN and TP losses, field monitored data from 18 runoff plots under natural rainfalls were used to analyze the changing characteristics of runoff, soil loss, and nutrient losses during 2014–2019. The results indicated that runoff, soil erosion, as well a TN and TP losses from the plots varied significantly, depending on land use and soil conservation measures. Bare plots suffered the highest soil, TN, and TP losses, followed by cultivated plots without soil conservation measures, cultivated plots with contour tillage, and other plots. Event-averaged runoff and soil loss rates ranged from 0 to 7.9 mm and from 0 to 444.4 t km−2 yr−1, and event-averaged TN and TP losses from cultivated plots were the highest, with values of 39.8 and 3.0 kg km−2, respectively. Bare and cultivated plots were the main sediment and nutrient sources. Among the cultivated plots, the terraced plot had the lowest soil and nutrient losses. The vegetated plots had insignificantly lower soil and nutrient losses. Most TN and TP were lost in particulate status from the plots, especially from the plots with soil conservation measures. Soil conservation measures can effectively prevent TN and TP losses. To guarantee water resource use, contour tillage is preferred for the bare and cultivated lands in the study region.

Adoption of Soil Conservation Measures

Land degradation resulting from soil erosion is a major problem in rain-fed agricultural areas in India. This study analyses the key determinants of farmers’ decisions to adopt on-farm soil and water conservation (SWC) measures in the rain-fed watershed areas of Siddipet district in Telangana. Here, SWC measures have been undertaken by the government and NGOs at the sub-watershed/community level and by individual farmers at the farm level. The study is based on a primary survey of over 400 farmers conducted in January–March 2018. In addition to estimating the influence of biophysical and market access variables on farmers’ decisions to undertake SWC practices, the study includes a logistic model that found a complementarity between community and individual plot-level interventions to improve soil health. The findings also highlight the influence of conservation measures practised in the neighbourhood on farmers’ decisions to implement SWC measures.

Water-Saving Soil Conservation Measures Should Be Used in Northern China: Evidence from Runoff Plot Data

Most of the current studies on soil conservation measures mainly focus on their soil control effect, neglecting their impact on water quantity. In the present study, the latest seven years (2014–2020) of monitored data from 22 runoff plots in the upstream catchment of the Miyun Reservoir, Beijing were used to evaluate the effects of slope, rainfall, and soil conservation measures on soil and water loss, and some implications were given in this water-scarce region. Excluding the impact of soil conservation measures, soil loss increased with the slope gradient and slope length. Runoff and soil loss were greatly affected by the rainfall amount and maximum 30-min rainfall intensity on the bare and cultivated slopes, or by rainfall amount and rainfall duration on almost all of the plots with soil conservation measures. The results indicated that the bare soil suffered the most severe soil loss, with a mean annual soil loss rate (SLR) of 4325 t km−2 year−1, followed by the cultivated lands without any measure, with an annual SLR of above 3205 t km−2 year−1. Contour tillage cannot effectively control soil loss on steep slopes. The vegetation measures and terrace, level bench, and fish scale pits, as well as their combinations, can decrease runoff by above 86% and decrease soil loss by 95%, respectively. Water-saving measures should be implemented in the study region. The measures, such as vegetation coverage, terracing, contour tillage, etc., should be carefully implemented on slopes. Bare and cultivated lands should further be implemented with soil conservation measures in this and similar regions in the world.