Leaching potential of S-metolachlor in a medium-textured Oxisol soil with bioindicator plants

ABSTRACT Information about the impact of herbicides in the soil based on the growth of bioindicator species is extremely useful in developing crop management strategies. Therefore, this study aims to evaluate the leaching potential of the herbicide S-metolachlor under different natural precipitations in medium-textured Oxisol using bioindicator plants. A completely randomized experimental design was adopted, with four replicates and treatments arranged in a 3 × 8 factorial scheme [three indexes of precipitation occurred in the environment before the collection of the samples (50, 91, and 131 mm) and eight depths in the soil profile (0-0.03; 0.03-0.06; 0.06-0.09; 0.09-0.12; 0.12-0.15; 0.15-0.20; 0.20-0.25; 0.25-0.30 m)]. PVC columns were used, maintaining the original soil integrity during sampling after accumulating the stipulated natural precipitation. Longitudinal sections separated the columns to sow the bioindicator species (cucumber, lettuce, Alexander grass, and sorghum). The phytotoxicity symptoms of bioindicator plants were evaluated, adopting a phytotoxicity visual scale between 0 and 100%, at 5, 7, 9, and 11 days after seeding. The responses of the bioindicator species to the residual effect of the herbicide S-metolachlor were variable and depended on the rainfall level. Generally, in a medium-textured Oxisol, the higher values of concentration of S-metolachlor occurs in depths ranging between 0 and 0.06 m. The maximum leaching depth detected was 0.12-0.15 m with 131 mm of precipitation. Cucumber was the most sensitive species to the presence of S-metolachlor in an Oxisol of medium-texture since it presents symptoms of phytotoxicity at higher depths.

Effects of Content of Soil Rock Fragments on Soil Erodibility in China

Soil erosion is serious in China—the soil in plateau and mountain areas contain a large of rock fragments, and their content and distribution have an important influence on soil erosion. However, there are still no complete results for calculating soil erodibility factor (K) that have corrected rock fragments in China. In this paper, the data available on rock fragments in the soil profile (RFP); rock fragments on the surface of the soil (RFS); and environmental factors such as elevation, terrain relief, slope, vegetation coverage (characterised by normalised difference vegetation index, NDVI), land use, precipitation, temperature, and soil type were used to explore the effects of content of soil rock fragments on calculating of K in China. The correlation analysis, typical sampling area analysis, and redundancy analysis were applied to analyse the effects of content of soil rock fragments on calculating of K and its relationship with environment factors. The results showed that (1) The rock fragments in the soil profile (RFP) increased K. The rock fragments on the surface (RFS) of the soil reduced K. The effect of both RFP and RFS reduced K. (2) The effect of rock fragments on K was most affected by elevation, followed by terrain relief, NDVI, slope, soil type, temperature, and precipitation, but had little correlation with land use. (3) The result of redundancy analysis showed elevation to be the main predominant factor of the effect of rock fragments on K. This study fully considered the effect of rock fragments on calculating of K and carried out a quantitative analysis of the factors affecting the effect of rock fragments on K, so as to provide necessary scientific basis for estimating K and evaluating soil erosion status in China more accurately.

Approaches towards Land Valuation and Land Pricing under the Influence of Geo-Climate Change

The Czech Republic is more or less unique in its dual system (official and market price) of agricultural land prices. In the case of the market price, there are several studies and approaches that assess the impact of individual variables on the market price of land. If we focus on the official price of land, its value in the Czech Republic is influenced by the evaluated soil ecological unit (ESEU) price. The ESEU price expresses the production potential of the land on the basis of soil quality indicators, which include the climatic region, the main soil unit, slope and exposure and, last but not least, the depth of the soil profile and skeletonisation. Climate change also means that the current values of the definition (e.g., for a climatic region, this refers to the average temperature or average precipitation) do not correspond to reality. No studies have looked in detail at the impact of soil quality indicators or climate change on the price of ESEUs. New and more accurate measurements of soil characteristics are increasing the number of ESEU codes, and prices have not yet been set for some codes. For this reason, we proposed the use of a hedonic method to determine shadow prices, which reflect the intensity and direction of the effect of each input variable on the price of an ESEU. A heteroscedastic corrected linear regression model was used to determine the coefficients, which presents in detail the effect of all included parameters on the final price of an ESEU in the results section. From the results, it was obvious that the shadow price coefficients themselves corresponded to basic generally accepted assumptions regarding the direction of effect. In the conditions of the Czech Republic, a significant influence on the price of an ESEU was mainly the slope with exposure and the depth of the soil profile with skeletonisation. These factors affected the productive capacity of the soil, which, in turn, translated into lower profitability of agricultural entities. The high explanatory ability of the hedonic model, with a high parametric significance for most of the used variables, was an important factor determining the robustness of the model as a repricing tool. The model set according to the prices of the applicable price decree can be used to set the prices of new or not-yet-valued ESEU codes under the conditions in the Czech Republic, or shadow prices can be used during climatic changes in the event of the transfer of the given soil unit to another climate region according to the general specification. It is therefore an important tool for the needs of the public administration.

Study of Soil Characteristics on Dryland Productivity of the Supiturung Micro Watershed, Kediri Regency

A study of soil characteristics dryland productivity of the Supiturung Micro Watershed, Kediri Regency, was conducted by observing the physical conditions of the environment and identifying the morphological and physical properties of the soil in each horizon in the soil profile. Parameters observed were physical properties (texture, bulk density) and chemical properties (CEC, total N, organic C, and base saturation). Data on soil characteristics and plant productivity were then analyzed by correlation and regression to determine the relationship between the two. The results showed that the soil in the study area belongs to the order Inceptisols and Entisols with the dominant subgroup Typic Humudepts. Pineapple plants were spread at SST 5, 7, 9, and 10 with the productivity of 71.18%, 76.35%, 75.76%, and 72%, respectively. Meanwhile, sugarcane was spread in SPL 1, 2, 3, 4, 6, and 8 with the productivity of 71%, 77%, 73.43%, 76.29, and 70.81%, respectively. The results of the analysis show that the land characteristics that affect the productivity of pineapple plants are sand texture with a correlation coefficient value of 0.84 and a regression of 0.71 with a linear equation y= -0.07x + 67.57 R² = 0.53 Land with a sand texture class increasingly has low productivity.

Changes in Soil Organic Carbon and Its Labile Fractions after Land Conversion from Paddy Fields to Woodlands or Corn Fields

Land use change could significantly affect soil organic carbon (SOC) and other soil chemical properties. However, the responses of soil labile C fractions at different soil depths to land-use change are not still clear. The aim of this study was to investigate the effect of paddy field conversion on woodlands or corn fields on total soil organic C (TOC) and its labile C fractions including particulate organic C (POC), microbial biomass C (MBC), and potassium permanganate-oxidizable C (KMnO4–C) along a 0–100 cm soil profile. Our results indicate that soil TOC concentrations increased by 3.88 g kg−1 and 3.47 g kg−1 in the 0–5 cm soil layer and 5.33 g kg−1 and 4.68 g kg−1 in the 5–20 cm soil layer during 13 years after the conversion from paddy fields to woodlands and corn fields, respectively. In the 20–40 cm soil layer, the woodlands had the highest TOC concentration (12.3 g kg−1), which was 5.13 g kg−1 and 3.5 g kg−1 higher than that of the paddy and corn fields, respectively. The increase in TOC was probably due to the absence of soil disturbance and greater root residue input into the woodland soil. In corn fields, pig manure addition contributed to the increase in soil organic C concentrations. In addition, the proportion of soil KMnO4–C increased after conversion from paddy fields to woodlands or corn fields in the 0–40 cm soil layer, ranging from 39.9–56.6% for the woodlands and 24.6–32.9% for the corn fields. The soil POC content was significantly higher in woodland and corn field soils than in paddy field soils at lower soil depths (5–40 cm). However, there were no differences in MBC contents in the whole soil profile between the woodlands and paddy fields. The KMnO4–C and MBC was the most important factor affecting the CMI values through the whole 0–100 cm soil profile. Overall, converting paddy fields to woodlands or corn fields increased the TOC and labile C fractions in the 0–40 cm soil layer. Future studies should focus on the response of the deeper soil C pool to land-use change.