•The spectral indices improve the performance of PTFs in estimating of SM.•Soil moisture is more accurately estimated by the combined NDWI and SWCI indices.•The accuracy of the RF for estimating the ...SM is better than the MLR-based PTFs.•Amount of clay in all functions has the most impact on estimating of SM.
To estimate the surface soil moisture (SM) using a combination of new spectral indices and methods of Random Forrest (RF) and Multiple Linear Regression (MLR), 11 pedotransfer functions (PTF1-11) were developed by combining basic soil properties (clay, silt/sand, and bulk density) and spectral indices of Sentinel-2 satellite. In this study, 124 surface soil samples were randomly taken from three regions including Telo in Tehran province, Ivaneki in Semnan province, and Borujerd in Lorestan province, Iran. The results showed that the accuracy of the RF method was considerably higher compared to the MLR method. The SM was better estimated using water spectral indices (such as Normalized Difference Water Index (NDWI) and Surface Water Capacity Index (SWCI)), along with the basic properties of soil as inputs of PTF7. In the training and testing steps, the Root Mean Square Error (RMSE) decreased from 0.041 and 0.05 (cm3 cm−3) in PTF1 to 0.028 and 0.039 in PTF7, respectively. The average values of RMSE, Akaike Information Criterion (AIC), coefficient of determination (R2) and Relative Improvement (RI) of the RF method were 0.028 (cm3 cm−3), −559, 0.79 and 0.001, and 0.038 (cm3 cm−3), −279, 0.73 and −0.006 for the training and testing steps of all PTFs, respectively. While, these values for the MLR method were 0.032 (cm3 cm−3), −542, 0.69 and 0.0003, and 0.043 (cm3 cm−3), −269, 0.63 and 0.002 for the training and testing steps, respectively. Due to the low values of MBE, it was possible to disregard the overestimation of the results. The evaluation of results for predictor importance indicated that among the basic properties, clay percent has a significant effect on estimation of SM. These results show that spectral indices alone are not suitable estimators for SM estimation. It suggests using basic soil properties and spectral indices to estimate the SM.
The occurrence and consequences of soil water repellency (SWR) have been reported in many parts of the world, but little is known on the existence of SWR in Iran. The purpose of the present study was ...to investigate the persistence of SWR in 10 forestry sites under different plant species (Pinus taeda, Alnus subcordata, Pterocarya fraxinifolia, Sambucus ebulus, Boxus sempervirens, Parotia persica, Quercus castanefolia, Fagus orientalis, Acer sp. and sparse grass) in North of Iran at Guilan province. The soils examined in this study include a broad range of textures, organic matter contents and pH levels. The persistence of SWR at the surface of the soil in the undisturbed samples (0–5cm, n=256) was collected at the areas, was measured using the Water Drop Penetration Time Test (WDPT). In the field, the actual water repellency was determined using the WDPT test but the same test was used to determine the potential water repellency after drying process for several days at 25°C in the laboratory. A wide range of SWR classes (hydrophilic to extreme water-repellent soils) has been found in sandy soils under pine, Alnus vegetation and broadleaves forests with silty loam, silty clay loam and clay loam texture, while inexistent or slight water repellency has been observed in soils under pine forest with clay contents >35%. Sampling was performed within 2 seasons (Autumn and Summer) and actual water repellency was only observed in forests in the Summer. The results showed a positive correlation between LogWDPT and organic matter content with r=0.41 (p=0·01, n=256). Comparing all soil samples together, low coefficients, r=−0.35 and 0.27 (p=0.01) between LogWDPT with clay and sand percentage were determined respectively. Soil pH had no significant effect on soil water repellency when all soil samples were compared together but when sites were compared separately, a negative and significant relation was detected between pH and LogWDPT. In this research, maximum water repellency was found in sandy soil samples with 5.26–11.5% organic matter. Field observations imply that SWR is not a static soil property and could be observed in field when soil becomes so dry. The results show that soil organic matter content, texture and pH are important factors for developing SWR in soil.
•We investigated the persistence of soil water repellency (SWR) in 10 forestry sites in North of Iran•SWR was present in field at dry period in summer and disappears when soil is wet during rainy season•Maximum water repellency were found in sandy soil samples with 5.26 –11.5% organic matter•The results show that soil organic matter content, texture and pH are important factors for developing SWR in soils.
One of the major contributors to air pollution, soil environmental degradations and health risks in paddy fields is the production of high volumes of rice growing activities’ wastes. Poorly managed ...rice husk and straw (such as burning) can be problematic since they threaten rice -based cropping system and farmers’ economy. One promising approach to decrease their negative effects is to use alternative managerial practices to guaranty both food security and sustainable agriculture and to address waste management issues. Currently, the burning rice wastes burning and off season’s tillage are two hot topics that is of interest to numerous agricultural researchers. The main purpose of this study was to explore the effects of rice residues burning on a number of crucial paddy soil chemical and physical characters, rice yield and yield component, rice pests, diseases, and common weeds populations. The current one -year field experiment was carried out in five factors factorial arrangement in a randomized complete block design with three replications. The treatments were tillage methods at three levels (non-plowing, autumn plowing, and winter plowing), and crop residues’ management at two levels (residues burning and residues conservation). The chemical (Total N, Zn content and OC %) and physical (infiltration rate) properties of paddy soil were significantly affected by residual management (p <0.05), except bulk density. The initial soil organic carbon percentage (2.18%) and consequently initial infiltration rate (2.04) increased at the conservative management of the residues in combination with plowing by around 0.51 percent, 2.69 and 2.81, respectively. Furthermore, the 1000 grains weight and filled grains weight were increased by abovementioned treatments by around 8 and 9percent, respectively. The rate of emergence of rice stem borer was negatively affected by winter and autumn plowing more than 4 times, with non- significant difference between winter and autumn plowing. The applied treatments had not any significant effect on studied rice weed populations, except weed 1 that tillage management caused a decrease about 2 times in its population. The applied treatments (alone and/or in combination) not only can certainly contribute to the reduction of rice weed, pest and disease populations but also strongly recommend to improve some important soil physical and chemical properties.
