Effects of soil and water conservation and its interactions with soil properties on soil productivity

The effects of soil and water conservation （SWC） on soil properties are well documented. However, definitive and quantitative information of SWC and its interactions with soil properties on soil productivity is lacking for hilly red soil region of southern China. Experiments were conducted in the hilly red soil region of southern China for seven years in three rtmoffplots, each of which represented different SWC forest-grass measures. Principal component analysis and multiple regression techniques were used to relate the aboveground biomass （representing soil productivity） to soil properties. Based on the final regression equations, soil organic carbon content （Sot） is significantly correlated with soil productivity under the condition of forest-grass measures, whereas pH value and cation exchange capacity （Cee） are the main factors for soil productivity without SWC. Therefore, SWC plays an important role in sequestering Soc and improving soil productivity.

Interaction of Carbon Dioxide Enrichment and Soil Moisture on Photosynthesis, Transpiration, and Water Use Efficiency of Soybean

Soybean (Glycine max (L.) Merrill) is one of the most important oil and protein sources in the world. Interactive effect of elevated carbon dioxide (CO2) and soil water availability potentially impact future food security of the world under climate change. A rhizotron growth chamber experiment was conducted to study soil moisture interactions with elevated CO2 on gaseous exchange parameters of soybean under two CO2 concentrations (380 and 800 μmol·mol-1) with three soil moisture levels. Elevated CO2 decreased photosynthetic rate (11.1% and 10.8%), stomatal conductance (40.5% and 36.0%), intercellular CO2 concentration (16.68% and 12.28%), relative intercellular CO2 concentration (17.4% and 11.2%), and transpiration rate (43.6% and 39%) at 42 and 47 DAP. This down-regulation of photosynthesis was probably caused by low leaf nitrogen content and decrease in uptake of nutrients due to decrease in stomatal conductance and transpiration rate. Water use efficiency (WUE) increased under elevated CO2 because increase in total dry weight of plant was greater than that of water use under high CO2 conditions. Plants under normal and high soil moisture levels had significantly higher photosynthetic rate (7% to 16%) favored by optimum soil moisture content and high specific water content of soybean plants. Total dry matter production was significantly high when plants grown under elevated CO2 with normal (74.3% to 137.3%) soil moisture level. Photosynthetic rate was significantly and positively correlated with leaf conductance and intercellular CO2 concentration but WUE was significantly negatively correlated with leaf conductance, intercellular CO2 concentration and transpiration rate. However, the effect of high CO2 on plants depends on availability of nutrients and soil moisture for positive feedback from CO2 enrichment.

Hillslope soil erosion and runoff model for natural rainfall events

By using the momentum theorem and waterbalance principle, basic equations of slope runoff were derived, soil erosion by raindrop splash and runoff were discussed and a model was established for decribing hillslope soil erosion processes. The numerical solution of the model was obtained by adopting the Preissmann format and considering the common solution-determining conditions, from which not only the runoff and soil erosion but also their processes can be described. The model was validated by ten groups of observation data of Soil Conservation Ecological Science and Technology Demonstration Park of Jiangxi Province. Comparisons show that the maximum relative error between simulation and experimental data is about 10.98% for total runoff and 15 % for total erosion, 5.2% for runoffprocess and 6.1% for erosion process, indicating that the model is conceptually realistic and reliable and offers a feasible approach for further studies on the soil erosion process.

Impact of Land-Use Practices on Sediment Yield in the Dhrabi Watershed of Pakistan

Soil erosion by water is one of the most important land degradation processes in the sloping rainfed lands in Pakistan. A study was conducted in the Dhrabi watershed of Pakistan to evaluate sediment yield associated with rainfall-runoff under various land-use practices. Five sub-catchments with sizes varying from 1.5 to 350 ha were selected for measurement of rainfall, runoff and sediment yield. Soil conservation techniques were also introduced to reduce the soil erosion. All runoff events occurred in the summer especially during monsoon season （July-September）. Sediment yield of two small gully catchments ranged from 4.79 to 8.34 t/ha/yr in 2009, a relatively dry year. In 2010, the annual sediment yield was 8.15 to 12.31 t/ha. Terraced catchment with arable crops produced annual 4.1 t/ha of sediment as compared to 12.31 t/ha by the adjacent gully catchment showing high potential of terraces in reducing erosion. Runoff coefficients calculated for these catchments vary from 0.09 to 0.75. The macro and micro nutrients present in the sediment indicate that these nutrients are being depleted due to soil erosion.

Elevation, Slope Aspect and Integrated Nutrient Management Effects on Crop Productivity and Soil Quality in North-west Himalayas, India

On farm bio-resource recycling has been given greater emphasis with the introduction of conservation agriculture specifically withclimate change scenarios in the mid-hills of the north-west Himalaya region（NWHR）. Under this changing scenario, elevation, slope aspect and integrated nutrient management（INM） may affect significantly soil quality and crop productivity. A study was conducted during 2009-2010 to 2010-2011 at the Ashti watershed of NWHR in a rainfed condition to examine the influence of elevation, slope aspect and integrated nutrient management（INM） on soil resource and crop productivity. Two years of farm demonstration trials indicated that crop productivity and soil quality is significantly affected by elevation, slope aspect and INM. Results showed that wheat equivalent yield（WEY） of improved technology increased crop productivity by -20%-37% compared to the conventional system. Intercropping of maize with cowpea and soybean enhanced yield by another 8%-17%. North aspect and higher elevation increased crop productivity by 15%-25% compared to south aspect and low elevation（except paddy）. Intercropping of maize with cowpea and soybean enhanced yield by another 8%-15%. Irrespective of slope, elevation and cropping system, the WEY increased by -30% in this region due to INMtechnology. The influence of elevation, slope aspect and INM significantly affected soil resources（SQI） and soil carbon change（SCC）. SCC is significantly correlated with SQI for conventional（R2 = 0.65＊）, INM technology（R2 = 0.81＊） and for both technologies（R2 = 0.73＊）. It is recommended that at higher elevation.（except for paddy soils） with a north facing slope, INM is recommended for higher crop productivity; conservation of soil resources is recommended for the mid hills of NWHR; and single values of SCC are appropriate as a SQI for this region.

Spatial and Temporal Analyses of Water Quality in the Dhrabi Watershed of Pakistan： Issues and Options

Monitoring water quality is important for maintaining a healthy watershed, but it is mostly ignored in watershed planning and management. In the Dhrabi watershed of Pakistan, the quality of surface water was monitored at 16 locations to assess suitability for irrigation over regular intervals during the period 2007-2010. Similarly, groundwater quality was monitored at 10 locations for drinking and irrigation purposes. There was high spatial and temporal variability in surface water quality. Electrical conductivity （EC） and residual sodium carbonate （RSC） either exceeded or fluctuated around permissible limits at most of the locations throughout the monitoring period. Therefore, the use of such water for irrigation needs special care, otherwise its prolonged use may pose soil salinity and sodicity problems. The trend of EC and RSC for groundwater was similar to that for surface water. Exchangeable Mg2＋ exceeded permissible limits for most of the surface water and groundwater samples. In addition, microbial analysis of groundwater revealed that only two out of eight monitoring points during August 2009, none out of eight points during February 2010, and one out of nine points during June 2010 provided water fit for drinking. Soil samples were collected from the catchment areas of the major contributing streams and from the beds of the Kallar Kahar Lake and the Dhrabi Reservoir. The soil samples from the catchments showed high salinity and sodicity that may be the cause of high salinity and sodicity in the streams. The highest EC, sodium adsorption ratio （SAP,） and exchangeable sodium percentage （ESP） in the bed samples from the Kallar Kahar Lake were about 43 dS/m, 56, and 45, respectively. These high values were due to the saline water brought into the lake with the runoff.

Intensified cropping reduces soil erosion and improves rainfall partitioning and soil properties in the marginal land of the Indian Himalayas

Environmental crises,land degradation,declining factor productivity,and farm profitability questioned the sustainability of linear economy-based existing agricultural production model.Hence,there is a dire need to design and develop circular economy-based production systems to meet the twin objectives of environmental sustainability and food security.Therefore,the productive capacity,natural resource conserving ability,and biomass recycling potential of four intensified maize-based systems viz.maize(Zea mays)+sweet potato(Ipomoea batatas)-wheat,maize+colocasia(Colocasia esculenta)-wheat,maize+turmeric(Curcuma longa),and maize+ginger(Zingiber officinale)were tested consecutively for three years(2020,2021 and 22)in a fixed plot manner at Dehradun region of the Indian Himalaya against the existing maize-wheat systems.The result showed that the maize+sweet potato-wheat system significantly reduced runoff loss(166.3 mm)over the maize-wheat system.The highest through fall(68.12%)and the lowest stem flow(23.54%)were recorded with sole maize.On the contrary,the maize+sweet potato system has the highest stem flow(36.15%)and the lowest through fall.Similarly,the maize+sweet potato system had 5.6 times lesser soil erosion and 0.77 t ha^(-1)higher maize pro-ductivity over the maize-wheat system.Furthermore,the maize+sweet potato system recorded significantly higher soil moisture(19.3%),infiltration rate(0.95 cm h^(-1)),and organic carbon(0.78%)over the rest of the systems.The maize+sweet potato system also recycled the highest nitrogen(299.2 kg ha^(-1)),phosphorus,(31.0 kg ha^(-1)),and potassium(276.2 kg ha^(-1))into the soil system.Hence,it can be inferred that concurrent cultivation of sweet potato,with maize,is a soil-supportive,resource-conserving,and productive production model and can be recommended for achieving the circular economy targets in the Indian Himalayas.

Temperature Sensitivity of Nitrogen Dynamics of Agricultural Soils of the United States

Soil temperature controls gaseous nitrogen losses through nitrous oxide (N2O) and ammonia (NH3) fluxes. Eight surface soils from agricultural fields across the United States were incubated at 10°C, 20°C, and 30°C, and N2O and NH3 flux were measured twice a week for 91 and 47 d, respectively. Changes in cumulative N2O and NH3 flux and net N mineralization at three temperatures were fitted to calculate Q10 using the Arrhenius equation. For the majority of soils, Q10 values for the N2O loss ranged between 0.23 and 2.14, except for Blackville, North Carolina (11.4) and Jackson, Tennessee (10.1). For NH3 flux, Q10 values ranged from 0.63 (Frenchville, Maine) to 1.24 (North Bend, Nebraska). Net soil N mineralization-Q10 ranged from 0.96 to 1.00. Distribution of soil organic carbon and total soil N can explain the variability of Q10 for N2O loss. Understanding the Q10 variability of soil N dynamics will help us to predict the N loss.

Effects of particle fractions on the Bingham yield stress and viscosity of fine-coarse particle suspensions

The rheological behaviors of highly concentrated fine particle suspensions(clay-silt-water mixtures)and coarse particle suspensions(coarse particles within a fine particle suspension)were investigated in this study.Experimental results demonstrated that the Bingham Fluid Model with two rheological parameters,Bingham yield stressand viscosity,wellcharacterized the rheological behavior of fine particle suspensions at shear rates between 4 and 20 s^(-1).The inclusion of coarse particles within a fine particle suspension induced an enhancement to the rheological parameters.The rheological parameters of a coarse particle suspension not only depend on its total particle fraction but also on its relative fine/coarse particle fractions.Empirical equations of these two parameters were proposed,quantitatively related to both fine and coarse particle fractions.Results indicated that the Bingham yield stress and viscosity are much more(an order larger)sensitive to changes in fine particle fraction than to changes in coarse particle fraction.

Farming methods impact on soil and water conservation efficiency under tea[Camellia sinensis(L.)]plantation in Nilgiris of South India

Growing of tea on sloping land without any soil and water conservation measures causes enormous soil loss especially in the initial years.For sound soil and water conservation planning,there is a need to evaluate the various conservation measures as related to the amount of expected runoff and soil erosion.In this context,a field study was conducted in the farmer's field in Nigiris of South India for evaluating the impact of farming methods on soil and water conservation eficiency under new tea plantation One year old B-6 tea clones were planted at double hedge spacing(135 cm×75 cm×75 cm)in two slopes(8-12%and 30-35%)with treatments viz,contour staggered trenches(CST),vegetative barrier(VB),CST alternate with VB,CST with cover crop of beans and farmers'practice of plantation.Minimum runoff(14.6%)was observed from CST with cover crop of beans followed by CST(15.4%)under 8-12%slope range with exactly similar trend in runoff from the plots under 30-35%slope.Contrary to runof,minimum soil loss was observed from CST(4.9 and 6.9t ha^(-1)yr^(-1))fllowed by CST with cover crop of beans(5.3 and 73 t ha^(-1)yr^(-1))under 8-12%and 30-35%respectively.Implementation CST and CST with cover crop of beans are resulted in better soil moisture under both the slope ranges in comparison to remaining measures as well as farmers'practice of plantation.Therefore,either CST alone or in combination with cover crop of beans are recommended for soil and water conservation under new tea plantation in the hill slopes.

Dynamic study of infiltration rate for soils with varying degrees of degradation by water erosion

Ultisols,widely distributed in tropical and subtropical areas of south China,are suffering from serious water erosion,however,slope hydrological process for Ultisols under different erosional degradation levels in field condition has been scarcely investigated.Field rainfall simulation at two rainfall intensities (120 and 60 mm/h) were performed on pre-wetted Ultisols with four erosion degrees (non,moderate,severe and very-severe),and the hydrological processes of these soils were determined.The variation of soil infiltration was contributed by the interaction of erosion degree and rainfall intensity (p < 0.05).In most cases,time to incipient runoff,the decay coefficient,steady state infiltration rate,and their variability were larger at the high rainfall intensity,accelerating by the increasing erosion severity.Despite rainfall intensity,the infiltration process of Ultisols was also significantly influenced by mean weight diameter of aggregates at the field moisture content,soil organic carbon and particle size distribution (R2 > 30%,p < 0.05).The temporal erodibility of surface soil and soil detachment rate were significantly and negatively correlated with infiltration rate (r <-0.32,p < 0.05),but less significant correlation was observed between sediment concentration and infiltration rate for most soils,especially at the high rainfall intensity.The variation of surface texture and soil compactness generated by erosion degradation was the intrinsic predominant factors for the change of infiltration process of Ultisols.The obtained results will facilitate the understanding of hydrological process for degraded lands,and provide useful knowledge in managing crop irrigation and soil erosion.

Relationship between granitic soil particle-size distribution and shrinkage properties based on multifractal method

The mechanical properties of granitic residual soils vary with depth due to changes in soil type and heterogeneity caused by weathering.The purpose of this study was to relate the spatial variation of particle-size distribution(PSD)of granitic soils with soil shrinkage parameters using multifractal theory.The heterogeneity of PSD and pedogenic processes were depicted in detail by multifractal dimensions.The PSD generally increased with the increase of profile depth in accordance with the variation of single fractal dimension(D)ranging from 2.45 to 2.65.The shrinkage limit was greatly influenced by the multifractal dimension parameters,including information dimension(D1)and capacity dimension(D0)(Adjusted R2=0.998,P<0.01),and the maximum linear extensibility(κv)was determined by spectral width(?α)and bulk density,with the latter explaining 89%of the total variance ofκv(P<0.01).Soil shrinkage characteristic curve was fitted by the modified logistic model(R2>0.97,root sum of squares<0.1),and the water variation corresponding to the maximum change rate of linear extensibility was determined by the silt content(R2=0.81,P<0.01).Overall,the shrinkage of granitic soils was primarily influenced by PSD and soil compactness.

Effect of gravel content on the detachment of colluvial deposits in Benggang

Accurately calculating detachment capacity is the most fundamental issue when establishing a soil erosion process model.Colluvial deposits of Benggang are typical soil-gravel mixtures,whereas the understanding of the soil detachment of colluvial deposits is limited.This work investigated the effects of the gravel contents on the soil detachment capacity of colluvial deposits and its hydrodynamic mechanism.The colluvial sample was collected in Anxi County,Fujian Province,Southeast China,and a small-sample scouring test was used.The slope steepness ranged from 18%to 84%,unit discharge ranged from 0.56×10^(-3)to 2.22×10^(-3)m^(2)s^(-1),and gravel content ranged from 0%to 70%.The results indicated that the gravel content is the primary factor that influences the detachment capacity,followed by the discharge and then the slope.The detachment capacity trend with the gravel content varied over different slopes and discharges.Stream power represents the best hydrodynamic parameter for modelling the detachment capacity of colluvial deposits and can be used to establish a fitting equation for the colluvium together with the mean weight diameter(MWD)(Nash-Sutcliffe efficiency(NSE)=0.96).As the gravel content increased,the soil erodibility parameters increased several folds,in some cases more than 10 folds,mainly because the soil shear strength decreased gradually.Meanwhile,as the gravel content increased,the gravel specific surface area increased,the obstruction of gravel to runoff increased,and the energy needed for runoff to overcome gravel obstruction increased,leading to 2-3 folds higher critical shear stress of runoff for soilgravel mixtures compared with pure soil.In summary,gravel can influence the detachment capacity by changing the soil properties,and the gravel content also affects the relationship between soil detachment capacity and the hydrodynamic parameters.These findings deepen the understanding of the influence of gravel on soil erosion and provide a basis for establishing a soil erosion process model in colluvial deposits.

Soil Respiration, Microbial Biomass C and N Availability in a Sandy Soil Amended with Clay and Residue Mixtures

Crop yields in sandy soils can be increased by addition of clay-rich soil, but little is known about the effect of clay addition on nutrient availability after addition of plant residues with different C/N ratios. A loamy sandy soil （7% clay） was amended with a clay-rich subsoil （73% clay） at low to high rates to achieve soil mixtures of 12%, 22%, and 30% clay, as compared to a control （sandy soil alone） with no clay addition. The sandy-clay soil mixtures were amended with finely ground plant residues at 10 g kg-l： mature wheat （Triticum aestivum L.） straw with a C/N ratio of 68, mature faba bean （Vicia faba L.） straw with a C/N ratio of 39, or their mixtures with different proportions （0% 100%, weight percentage） of each straw. Soil respiration was measured over days 0-45 and microbial biomass C （MBC）, available N, and pH on days 0, 15, 30, and 45. Cumulative respiration was not clearly related to the C/N ratio of the residues or their mixtures, but C use efficiency （cumulative respiration per unit of MBC on day 15） was greater with faba bean than with wheat and the differences among the residue mixtures were smaller at the highest clay addition rate. The MBC concentration was lowest in sole wheat and higher in residue mixtures with 50% of wheat and faba bean in the mixture or more faba bean. Soil N availability and soil pH were lower for the soil mixtures of 22% and 30% clay compared to the sandy soil alone. It could be concluded that soil cumulative respiration and MBC concentration were mainly influenced by residue addition, whereas available N and pH were influenced by clay addition to the sandy soil studied.

Parameter evaluation for soil erosion estimation on small watersheds using SWAT model

This research was undertaken for the evaluation of soil erosion using the semi-distributed basin scale SWAT model for four subcatchments of the Dhrabi River Catchment(DRC),which is located in the Pothwar Plateau region.Two subcatchments(catchment-25 and-31)are characterized by gullies while the other two(catchment-27 and-32)are managed with terraced landuse system.The performance of the model was satisfactory with coefficient of determination(R^(2))=0.67 to 0.91 and Nash-Sutcliffe efficiency(ENS)=0.54 to 0.85 for both surface runoff and sediment yield during the calibration(2009-2010)and validation(2011)periods.The PUSLE factor was found to be the most sensitive parameter during model calibration.It was observed that all of the rainfall-runoff events occurred during the monsoon season(June to September).The estimated annual sediment loss ranged from 2.6 t/hm^(2) to 31.1 t/hm^(2) over the duration of the simulation period for the non-terraced catchments,in response to annual precipitation amounts that were between 194.8 mm to 579.3 mm.In contrast,the predicted annual sediment levels for the terraced catchments ranged from 0.52 t/hm^(2) to 10.10 t/hm^(2) due to similar precipitation amounts.The terraced catchments resulted in 4 to 5 times lower sediment yield as compared to non-terraced catchments.The results suggest that there is a huge potential for terraces to reduce soil erosion in the DRC specifically and Pothwar area generally,which have proven to be an efficient approach to establishing soil and water conservation structures in this region.

Developing a new red band- SEVI-blue band (RSB) enhancement method for recognition the extra-high-voltage transmission line corridor in green mountains

Monitoring the extra-high-voltage transmission line corridor(EHVTLC)in mountains is critical for safe smart-grid operation.However,the transmission lines are so narrow that they are difficult to recognize using multispectral satellite images with a spatial resolution of 10 m.In this study,we developed a new method using the red band–shadow-eliminated vegetation index(SEVI)–blue band(RSB)composite image to enhance the EHVTLC in green mountains(named RSB-enhancement method).Using this method,the EHVTLC becomes evident in the false-color synthesis of the RSB composite of the Sentinel-2 image.Then,we recognized and extracted approximately 342.45 km of the EHVTLC in a mountainous region of Fuzhou City,China,including a 46.73 km three-parallel-lane segment of 1000 kV and a 295.72 km two-parallel-lane segment of 500 kV.Spatial analysis shows that the SEVI mean difference between the EHVTLC and the buffer zone reaches approximately 10%,and three landslides and 2.66 km^(2) soil erosion reside in the buffer zone which area is approximately 73.67 km^(2).Finally,the RSB-enhancement method can be used in other satellite images with spatial resolutions of greater than 10 m for enhancement and recognition the transmission line corridors in green mountains.

Breeding for pre-harvest sprouting resistance in bread wheat under rainfed conditions

Pre-harvest sprouting in wheat is the germination of seeds within the spikes when rains occur after or during grain ripening, which occurs commonly in the barani tract of Pakistan. Therefore, 10 cultivars and five advanced lines of spring bread wheat were evaluated for pre-harvest sprouting resistance. After natural rainfall,seeds were immediately collected from the wet spikes and tested for germinating ability. Three different germination tests were applied to hand-threshed seed:(1) spikes threshed on the day of sampling and germination tested immediately,(2) spikes threshed on the day of sampling and germination tested 1 week later, and(3) spikes threshed 1 week after sampling and germination test immediately after threshing. Seeds and spikes kept for 1 week were place on blotting paper at room temperature.Cultivars BARS-09, 09 FJ17, Doukkala-12, NARC-09 and Ouassou-20 exhibited higher sprouting resistance while other genotypes were susceptible to pre-harvest sprouting in each of the three tests. A diallel crossing was conducted with six susceptible and two resistant genotypes to assess the genetic behavior of pre-harvest sprouting resistance.The combining ability(CA) demonstrated a higher proportion of additive genetic effects for sprouting resistance, because of higher variance of general and specific CA for both parameters under study. Doukkala-12 and BARS-09 showed increased pre-harvest sprouting resistance in their F1 descendants.