Increased Soil Water Research Articles

Farmland Hydrology Cycle and Agronomic Measures in Agroforestry for the Efficient Utilization of Water Resources under Karst Desertification Environments

Severe soil-water loss and unfertile soil frequently occur under karst desertification environments. The surface-underground dual structure in these areas allows the surface water to leak into the subsurface through cracks and sinkholes, as well as other conduits, causing a special “karst drought”. Hence, water-resource shortage has become a challenge for local agricultural development. To realize efficient utilization of water resources, an urgent need is to clearly understand and study the law of farmland hydrological cycles under agroforestry practices, which is still understudied. Here, we focused on the hydrological cycle at the farmland scale and water-saving measures under agroforestry in three study areas representing different degrees of karst desertification. First, a significant positive correlation was found between total and available precipitations as well as land evapotranspiration (LET). Second, under agronomic measures, the soil water content in the three areas was all higher than that of the control group while soil evaporation was all lower. This indicates that agronomic measures can contribute to the efficient use of water resources by halting soil evaporation and increasing soil water content. Third, dwarf dense planting and pruning technologies were helpful in inhibiting crop transpiration and reducing vegetation interception. Fourth, in the farmland hydrological cycle of agroforestry, 77.45% of precipitation transformed into soil water storage, 24.81% into soil evaporation, 20.73% into plant transpiration, 17.40% into groundwater, and 5.18% into vegetation interception. However, their sum was greater than 100%, suggesting that the farmland-scale water cycle is an open system. The implication is that different agronomic practices under agroforestry bring certain water-saving benefits by constraining the conversion of ineffective water and promoting the storage of effective water, thus opening up promising opportunities for efficiently utilizing water resources in karst desertification areas. The finding is also significant to the control of karst desertification, soil and water conservation, and karst drought alleviation.

Growth Response of Tartary Buckwheat to Plastic Mulching and Fertilization on Semiarid Land

Integrated hole-sowing, fertilization, and plastic mulching techniques are common agronomic practices applied to collect rainwater and to improve rainwater utilization in semiarid rain-fed regions. However, little is known about the growth responses of tartary buckwheat (Fagopyrum tataricum L.) to the practices adopted in semiarid areas of Loess Plateau in Northwest China. To address the concerns, a long-term field experiment was conducted in 2015–2017. Four fertilization levels, namely, high fertilization level (N–P2O5–K2O: 120–90–60 kg ha−1, HF), moderate fertilization level (80–60–40 kg ha−1, MF), low fertilization level (40–30–20 kg ha−1, LF), and zero fertilization level (ZF), were applied to hole-sown tartary buckwheat with whole plastic mulching, in comparison to the control with no-mulching and zero fertilization (CK). Several key growth-influencing indicators were measured in the consecutive experimental years, including soil temperature (Ts), soil water storage (SWS), leaf area index (LAI), dry matter (DM), and grain yield. The results showed that in different precipitation years, 2015 (193 ± 23 mm), 2016 (149 ± 19 mm), and 2017 (243 ± 28 mm), the ZF, LF, MF, and HF treatments had the potential to optimize Ts in 0~25 cm soil layers (at 5 cm interval). The four treatments improved SWS in 0~300 cm soil layers by 3.5% and increased soil water consumption in the pre-anthesis period by 22.4%, compared with CK. Moreover, the four treatments shortened the pre-anthesis growth period by 0.4~5.4 d, while extended the post-anthesis growth period by 5.7~10.0 d, giving rise to an overall extension of 0.6~5.0 d for a whole growth period of tartary buckwheat. Furthermore, the ZF, LF, MF, and HF treatments increased LAI by 4.4~225.3% and DM weight by 41.5~238.0%. The rain yield of the four treatments was increased by 14.0~130.4%, and water use efficiency (WUE) was improved by 11.3~102.7%, especially for the LF treatment, compared with CK. The study indicated that the technique of hole-sowing and plastic mulching combined with a low fertilization rate was an effective measure for tartary buckwheat to optimize crop growth and to boost grain yield and WUE on semiarid lands.

Revealing the Effect of Saline Water Drip Irrigation on Soil Microorganisms in Cotton Fields Based on Metagenomics

Saline water irrigation has become an important means to alleviate the shortage of freshwater in arid areas. However, long-term saline water irrigation can cause soil salinity accumulation, affect soil microbial community structure, and then affect soil nutrient transformation. In this study, we used metagenomics to investigate the effects of long-term saline water drip irrigation on soil microbial community structure in a cotton field. In the experiment, the salinity of irrigation water (ECw) was set to two treatments:0.35 dS·m-1 and 8.04 dS·m-1 (denoted as FW and SW, respectively), and the nitrogen application rates were 0 kg·hm-2and 360 kg·hm-2 (denoted as N0 and N360, respectively). The results showed that saline water irrigation increased soil water content, salinity, organic carbon, and total nitrogen content and decreased soil pH and available potassium content. Nitrogen fertilizer application increased soil organic carbon, salinity, and total nitrogen content and decreased soil water content, pH, and available potassium content. The dominant bacterial phyla in each treatment were:Proteobacteria, Actinobacteria, Acidobacteria, Chloroflexi, and Gemmatimonadetes. Saline water irrigation significantly increased the relative abundances of Actinobacteria, Chloroflexi, Gemmatimonadetes, and Firmicutes but significantly decreased the relative abundances of Proteobacteria, Acidobacteria, Cyanobacteria, and Nitrospira. Nitrogen fertilizer application significantly increased the relative abundances of Chloroflexi and Nitrospira but significantly decreased the relative abundances of Acidobacteria, Gemmatimonadetes, Planctomycetes, Cyanobacteria, and Verrucomicrobia. LEfSe analysis showed that saline water irrigation had no significant effect on the number of potential biomarkers, and nitrogen fertilizer application decreased the number of potential biomarkers in soil microbial communities. The correlation network diagram showed that the 20 genera had different degrees of correlation, including 44 positive correlations and 48 negative correlations. The core species in the network diagram were Nocardioides, Streptomyces, Pyrinomonas, Candidatus_Solibacter, and Bradyrhizobium spp. Saline water irrigation increased the relative abundances of the denitrification genes nirK, nirS, nasB, and norC and decreased the relative abundances of the nitrification genes amoB, amoC, and nxrA, whereas nitrogen fertilizer application increased the relative abundances of the nitrification genes amoA, amoB, amoC, hao, and nxrA and decreased the relative abundances of the denitrifying genes narB, napA, nasA, and nosZ. Saline water irrigation could adversely affect soil physicochemical properties; SWC, EC1:5, and BD were the main driving factors affecting soil microbial community structure and function genes; and soil microorganisms adapted to soil salt stress by regulating species composition.

Effect of Biochar Application on Soil Fertility, Nitrogen Use Efficiency and Balance in Coastal Salt-Affected Soil under Barley–Maize Rotation

Coastal lands are often affected by salinization, which leads to a deterioration of soil structure and a decrease in land productivity. As a widely used soil amendment, biochar has been proven to improve poor soil properties and promote crop growth and N adsorption and utilization. However, the effects of biochar on soil fertility, N use efficiency (NUE) and balance in coastal salt-affected soil have rarely been reported. Therefore, we conducted a field micro-plot experiment to study the improvement effects of different biochar rates (0, 13.5, 20.25 and 27 t/ha, corresponding to CK, B1, B2 and B3 treatments, respectively) on coastal salt-affected soil. The results showed that biochar application increased soil water content (SWC) in seasons with abundant rainfall but decreased SWC in seasons with strong evaporation, and the increase or decrease in SWC was greater with the increase in biochar rates. Biochar application increased soil salinity and decreased soil pH, although high rates of biochar increased soil salinity to a lesser extent, while low rates of biochar decreased soil pH most. Biochar application was able to reduce soil bulk density, while B1and B2 treatments decreased it to a higher degree. Moreover, biochar application increased soil macro-aggregates (>0.25 mm) and organic matter, while B2 and B3 treatments increased it to a higher degree. Biochar application improved soil fertility to an extent that crop grain increased yield by 2.84~19.88% in barley season and 12.27~16.74% in maize season. Meanwhile, biochar application also increased NUE because it promoted the increase of yield. In particular, the calculation of N balance between soil and plant systems suggested that biochar application could reduce the apparent N loss during crop planting, and B1 treatment was better at reducing apparent N loss. Overall, our study indicates that biochar application has great potential to improve poor physicochemical properties and N nutrient utilization in coastal salt-affected soil. More importantly, we suggest that biochar application rates should be controlled in coastal salt-affected soil.

The constancy of chemical weathering intensity on hillslopes in the arid to semiarid Qilian Mountains, NE Tibetan Plateau

Quantifying the relationship between the chemical weathering and denudation rates of active orogenic belts over a range of climates is the key to addressing the controversy over the uplift-weathering hypothesis. However, studies have focused on warm and humid environments and have not examined cold and arid environments. Here, we present a new dataset of the chemical depletion fraction (CDF: ratio of the chemical weathering rate to the total denudation rate) across the arid to semiarid Qilian Mountains on the northeastern Tibetan Plateau, where the uplift-weathering hypothesis has been proposed. We selected 60 points from 12 catchments in the middle Qilian Mountains. At each point, we collected three samples (soil, saprolite, and bedrock samples) and calculated the CDF values based on their Zr concentrations. We found no clear correlation between the CDF and climatic factors (temperature, precipitation, and normalized difference vegetation index (NDVI)), topographic factors (slope and local relief), and denudation rate. The calculated chemical weathering rates, nevertheless, are positively correlated with precipitation, NDVI, and denudation rate, and negatively correlated with temperature. This result indicates that the Qilian Mountains are under supply-limited conditions, even at high denudation rates (>800 t km−2 y−1). We speculate that low temperatures (<0 °C) could intensify near-surface chemical weathering by promoting the physical breakdown of the bedrock and increasing soil water availability. This mechanism causes a compensation effect maintaining the supply-limited conditions in landscapes with high denudation rates. Combing a worldwide dataset regarding the correlations between CDF and climatic factors and denudation rates, we argue that intensified denudation since the late Cenozoic contributed to global cooling.

Root distribution, soil water depletion, and water productivity of sweet corn under deficit irrigation and biochar application

Root modifications can play a vital role in crop adjustments to soil water deficit. It is important to understand root growth and soil water depletion patterns to develop effective cropping systems, especially in semi-arid regions like Texas High Plains (THP). This study evaluated root growth, soil water depletion, and water productivity (WP) of sweet corn under three deficit irrigation treatments [100 %, 70 % and 40 % crop evapotranspiration (ETc)] and biochar application (hardwood and softwood). The experimental units were replicated 4 times in a split-plot design. The results revealed no interaction between irrigation and biochar treatments for almost all measured parameters. The 70 % ETc treatment increased the root length density (RLD) over 100 % ETc during 2019, while no differences were observed among irrigation treatments in 2020. Both deficit irrigations (70 % and 40 % ETc) increased soil water depletion compared to 100 % ETc, the highest being in 40 % ETc. The 70 % ETc maintained a similar yield and increased WP by 21 % compared to 100 % ETc across two years. However, 40 % ETc resulted in significant decline in yield and WP in 2020. The hardwood biochar increased RLD over no biochar treatment without affecting the soil water status and WP. Long-term studies are needed to investigate biochar effects beyond two years of application. In case of limited water availability, 70 % ETc can be recommended as an alternative to 100 % ETc in the THP of the US.

Effects of arbuscular mycorrhizal fungi on plant growth and herbivore infestation depend on availability of soil water and nutrients.

Fitness of plants is affected by their symbiotic interactions with arbuscular mycorrhizal fungi (AMF), and such effects are highly dependent on the environmental context. In the current study, we inoculated the nursery shrub species Artemisia ordosica with AMF species Funneliformis mosseae under contrasting levels of soil water and nutrients (diammonium phosphate fertilization), to assess their effects on plant growth, physiology and natural infestation by herbivores. Overall, plant biomass was synergistically enhanced by increasing soil water and soil nutrient levels. However, plant height was surprisingly repressed by AMF inoculation, but only under low water conditions. Similarly, plant biomass was also reduced by AMF but only under low water and nutrient conditions. Furthermore, AMF significantly reduced leaf phosphorus levels, that were strongly enhanced under high nutrient conditions, but had only minor effects on leaf chlorophyll and proline levels. Under low water and nutrient conditions, specific root length was enhanced, but average root diameter was decreased by AMF inoculation. The negative effects of AMF on plant growth at low water and nutrient levels may indicate that under these conditions AMF inoculation does not strongly contribute to nutrient and water acquisition. On the contrary, the AMF might have suppressed the direct pathway of water and nutrient absorption by the plant roots themselves despite low levels of mycorrhizal colonization. AMF inoculation reduced the abundance of the foliar herbivore Chrysolina aeruginosa on plants that had been grown on the low nutrient soil, but not on high nutrient soil. Fertilization enhanced the abundance of this herbivore but only in plants that had received the high water treatment. The lower abundance of the herbivore on AMF plants could be related to their decreased leaf P content. In conclusion, our results indicate that AMF negatively affect the growth of Artemisia ordosica but makes them less attractive to a dominant herbivore. Our study highlights that plant responses to AMF depend not only on the environmental context, but that the direction of the responses can differ for different components of plant performance (growth vs. defense).

Maize straw mulching with no-tillage increases fertile spike and grain yield of dryland wheat by regulating root-soil interaction and nitrogen nutrition

Straw mulching increases soil water availability, but the influence of tillage practices with straw mulching on soil water, soil nitrogen, root distribution, and the physiological response of wheat plants is poorly understood. Field experiments (2013–2017) were conducted to determine the combined effects of straw mulching (0 and 8,000 kg ha−1) and tillage methods (no-tillage, rotary tillage, and plow tillage) on soil water, N, root distribution, plant N nutrition, tiller capability, and grain yield of dryland wheat. Straw mulching with no-tillage showed higher soil moisture, mineral N, and Olsen-P content than no-mulch with rotary tillage or plow tillage. These changes increased the total root length and surface area in the 0–20 cm soil layer but not in the 20–40 cm soil layer. Topsoil foraging strategies of root increased total N uptake, wheat return N from straw, and N balance while reducing N surplus, indicating that maize straw harvesting by mulching with no-tillage leads to a more efficient N recycling in the winter wheat–summer maize rotation system. Straw mulching with no-tillage showed greater aboveground plant dry mass and shoot N%, leading to increased plant N nutrition, tillering capability, and grain yield. Our results indicated that maize straw mulch with no-tillage increased fertile spike and grain yield by increasing soil water and N availability and maximizing root-soil interactions among the different combinations studied. Maize straw mulching with no-tillage could hence be recommended to dryland farming communities to transition from rotary tillage to a no-tillage conservation system and to increase soil and crop productivity in the maize-wheat rotation system.

Biochar co‐compost improves nitrogen retention and reduces carbon emissions in a winter wheat cropping system

AbstractOrganic amendments, such as compost and biochar, mitigate the environmental burdens associated with wasting organic resources and close nutrient loops by capturing, transforming, and resupplying nutrients to soils. While compost or biochar application to soil can enhance an agroecosystem's capacity to store carbon and produce food, there have been few field studies investigating the agroecological impacts of amending soil with biochar co‐compost, produced through the composting of nitrogen‐rich organic material, such as manure, with carbon‐rich biochar. Here, we examine the impact of biochar co‐compost on soil properties and processes by conducting a field study in which we compare the environmental and agronomic impacts associated with the amendment of either dairy manure co‐composted with biochar, dairy manure compost, or biochar to soils in a winter wheat cropping system. Organic amendments were applied at equivalent C rates (8 Mg C ha−1). We found that all three treatments significantly increased soil water holding capacity and total plant biomass relative to the no‐amendment control. Soils amended with biochar or biochar co‐compost resulted in significantly less greenhouse gas emissions than the compost or control soils. Biochar co‐compost also resulted in a significant reduction in nutrient leaching relative to the application of biochar alone or compost alone. Our results suggest that biochar co‐composting could optimize organic resource recycling for climate change mitigation and agricultural productivity while minimizing nutrient losses from agroecosystems.

Rice-based Cropping System Intensification in the Coastal Saline area of Bangladesh: Problems and Prospects

The coastal zone environment of Bangladesh is characterised geographically by river deltas and estuaries, where tidal and riverine flooding and varying salinity levels affect agriculture and livelihoods. In this area, the land and agricultural productivity is very low because of several constraints, particularly waterlogging, high salinity of soil and water, freshwater scarcity for crop irrigation and natural disaster. In this review, the objectives are to focus on the limiting factors for crop intensifying and highlighting the opportunities to increase coastal agriculture while enhancing farmer’s livelihoods. Some recent studies demonstrated many opportunities for increasing cropping systems that have not yet been exploited extensively. Rainwater or low saline river water storing in the internal canal can fulfil the water requirement for dry season rice and non-rice crops, thereby increasing growth and yield. Early establishment of “Rabi” crops (non-rice) can utilize maximum low-saline soil water and escape high salinity/drought or heat/storms at later period of the growing stages, but this early sown Rabi crops needs early harvest of Aman rice around 15-30 days earlier than farmer practices. Moreover, early sowing by zero tilled dibbling (such as sunflower, maize, wheat, and potato) in wet soils results in higher yield potential. Using rice straw mulch ~5 t ha-1 has been shown to be highly beneficial for ameliorating soil constraints. A recent study revealed that straw mulch application on soil surface increased soil water and soil solute potential in the upper root zone, reduced soil salinity, soil strength, and cracking which attributed to higher yield. Considering the successful dry season crop establishment and yield potential requires early drainage to remove excess soil water and a drainage system that mitigates waterlogging from heavy rainfall events during the growing season. We expect this review will facilitate the future research planning and execution in this vulnerable coastal environment. Bangladesh Rice J. 25 (2) : 31-43, 2021

Mesh-shelters provide more effective long-term protection than tube-shelters or mulching for restoration of Pinus halepensis in a Mediterranean arid ecosystem

Forest restoration is challenging in arid and semiarid lands. Research has identified ecotechnologies that may alleviate stressful conditions of planted seedlings, but studies are often limited to the first few years of regeneration establishment. Over 20 years, we tested the effects of tree shelters (mesh- and tube-shelters) and competition suppression (two types of synthetic mulch and manual weeding) on soil water content and development of Pinus halepensis on an arid site in southeastern Spain. Competition suppression increased soil water content at shallow depths only using a polyethylene sheet, with no effect on survival. Tree shelters had a much greater effect than competition suppression on tree responses. Survival was mostly affected by shelter type, with lower survival in tube-shelters compared to mesh-shelters and non-protected seedlings; differences began after the first year, but became more pronounced following an intense drought at 3 years. Survival for pines protected by mesh-shelters was significantly higher than for non-protected seedlings beginning at 6 years, and mortality did not stabilize until 15 years. After 20 years, survival ranked in order of mesh-shelters (57.5%), non-sheltered (46%), and tube-shelters (29.5%). Effects of shelter type on growth response over time followed an opposite pattern, with differences declining when pines outgrew the height of the shelter after 3 years. The response of pines to tube-shelters could be explained by the microenvironmal differences among vertical protection and its effects on a shade intolerant species such as Pinus halepensis: survival depletion is provoked probably by a reduction in root growth under the shaded conditions of tubes. On the other side, growth and morphology response could be partially explained by differences in light, but response of pines in mesh also points towards a reduction of wind pressure that precludes stem growth in thickness. Competition suppression had no effect on pine growth. Lack of response to main effects of competition suppression treatments can be attributed to the minimum changes of soil water content to mulching or weeding under arid conditions. Thus, 20 years after planting, tube-shelters and competition suppression treatments were relatively ineffective at improving survival or growth of P. halepensis. Mesh-shelters are recommended as the most effective protection method for restoration under arid site conditions.

The roles for branch shelters and sheep manure to accelerate the restoration of degraded grasslands in northern China

New strategies are desperately needed for restoring the millions of hectares of degraded grasslands in arid and semiarid areas of northern China. This study evaluated using different combinations of manure amendments and shrub branch shelters for their impacts on soil moisture, nutrient availability, and plant growth over two growing seasons in a degraded grassland in Ningxia, China. A two-factor experiment was conducted, with three concentrations of 1.2 g m−2, 442 g m−2, and 884 g m−2 native Tan sheep manure as the main plots. Cut caragana (Caragana intermedia) branches were used to create branch shelters covering 0%, 20%, 40%, and 60% of ground area, and these acted as sub-main plots. Soil water storage, soil temperature, manure decomposition, branch decomposition, soil nutrients, and plant growth were monitored for 2 years. Results indicated that soil water storage was significantly increased, and soil temperature decreased, under the 40% and 60% branch shelters. Decomposition rate of manure and shrub branches also increased with increasing soil water availability associated with the higher branch sheltering effects, although soil carbon and nitrogen concentrations were primarily driven by the decomposing manure. The combination of high levels of shrub branch shelter and manure application significantly enhanced plant production, although the bulk of the biomass was concentrated in one species, Artemisia scoparia. In conclusion, our study successfully demonstrated feasible and inexpensive solution for the restoration of degraded grasslands, which takes advantage of resources associated with overgrazing Tan sheep and Caragana shrub encroachment in arid and semiarid areas.

Effect of Grass Components on the Temporal Response of Surface Soil Water to Precipitation and Air Temperature in the Loess Plateau

The Loess Plateau of China is facing increasingly serious challenges related to water shortage issues despite the successful vegetation restoration. Surface soil water (0–40 cm) is crucial to water transfer and discharge in the soil-plant-atmosphere continuum, which is controlled by precipitation (P), air temperature (Ta), and plant components. This study selected one typical grass species and set different treatments of natural condition (NC), removing litter (CR), and only roots (OR), to analyze the responses of soil water storage (W) and its change (∆W) to P and Ta at different time scales (including daily, weekly and monthly scales). The results showed that P had significantly positive effects on W and ∆W, while Ta negatively influenced W and ∆W. Meanwhile, Ta also controlled the significance of P affecting W. P contributed more (53–63%) to ∆W variation at the daily scale, but Ta showed more effect (73–80%) at the weekly scale, and both of them contributed more than 77% at the monthly scale. P and Ta existed a threshold phenomenon for increasing soil water, where P thresholds were higher than 0.93, 4.98, and 28.17 mm and Ta threshold were lower than 28.69, 28.89, and 29.96°C at the daily, weekly and monthly scales, respectively. Moreover, grass components also affected the responses of ∆W to P and Ta, and the OR treatment displayed the lowest sensitivity and had the lowest loss rate of soil water. The total infiltration, total loss amount, and rainwater retention rate exhibited: NC &gt; CR &gt; OR. Overall, grass canopy and litter improved soil water condition, and the roots most strongly protected soil water after infiltration. This study can provide a better understanding of surface soil water responding to climate change under drought stress with water shortage implications, and may strength the management of grassland in semi-arid region.

Ferrihydrite coating reduces microplastic induced soil water repellency.

Addition of microplastics (MP) to soil has the potential to increase soil water repellency. However, coating of MP with soil abundant substances e.g., iron compounds, can reduce this effect. Here, we tested if pre-coating or in situ coating of MP with ferrihydrite (Fh) reduces soil water repellency. We applied hotspots of pristine and coated MP (20-75 μm, PS and PET) to sand and imaged capillary rise via neutron radiography. Capillary rise experiments in wetting-drying cycles were conducted using water and Fh suspension. Pristine MP hotspots were not wettable. Capillary rise of water into coated MP hotspots differed in wettability depending on polymer type. While coated PS was still non-wettable, water imbibed into the coated PET hotspot. Capillary rise of Fh suspensions in wetting and drying cycles also showed varying results depending on polymer type. MP hotspots were still non-wettable and local water content increased only marginally. Our results indicate that Fh coating of MP changes MP surface wettability depending on polymer type and therefore counteracts the hydrophobic properties of pristine MP. However, MP coating is likely to be slowed down by the initial hydrophobicity of pristine MP. Dynamics of MP coating and increasing wettability are key factors for biotic and abiotic degradation processes.

Effect of Organic Mulch and Water Supply on Yield and Profitability in Black Nightshade (Solanum Scabrum Mill.) in West Cameroon

Water shortage and increased soil water evaporation are among challenges facing farmers in tropical regions subjected to prevailing climate change. Combinations of agricultural practices expected to improve yields of cultivated crops such as mulching has been described as a method to improve soil water storage and yields of cultivated crops including black nightshade. Unfortunately, up to date, few research works have addressed the yields and profitability of black nightshade. Combinations of rate of water, frequency of irrigation, mulch rate were tested during the 2021 and 2022 off-seasons for large-scale and cost-effective production of black nightshade, a staple food crop. A total of 18 triptych combinations of three irrigation volumes (Vn), three irrigation frequencies (Fn) and two mulch rates (Mn) were tested. Results showed that the best 5 yielding combinations (mean: 42.08 t/ha) represented 124% of the trial mean (33.80 t/ha) independently of the cropping year. However, combination V1F3M10 i.e. applying an average of 5.8 mm/day of water every 3 days on 10 t/ha-mulch plots led to the highest yield (47.16 t/ha) and profit (304.60%). Therefore, the combination V1F3M10 should be adopted for off-season production of black nightshade on Oxisol from West-Cameroon. Soil mulching at 10 t/ha promoted water saving by 402.3 mm and probably reduced soil water evaporation, weeds control, and improved water use efficiency.

Drivers of Variation in Winter and Spring Groundwater Recharge: Impacts of Midwinter Melt Events and Subsequent Freezeback

AbstractIn areas with seasonal snowfall, the spring snowmelt often accounts for a large percentage of annual groundwater recharge. As climates warm, midwinter snowmelts are becoming more common. Although midwinter melt events can cause discrete recharge events, they can also increase soil water content and leave the ground exposed to subsequent cold periods. Without the insulating effects of snow, frozen ground can develop, which can prevent infiltration during subsequent melt events, reducing recharge, and increasing overland flow. We investigated relationships between winter precipitation, the soil thermal regime, and recharge to determine the factors that contribute to variation in winter‐spring recharge. We found that statistically significant predictors of variation in winter‐spring recharge, controlling for precipitation, were amount and cover of snow, evapotranspiration/sublimation, air temperature, and number of freezeback events occurring between two melt events. We observed that midwinter snowmelt followed by freezeback and subsequent melt events correlated with lower than expected recharge. We quantify the occurrence of this sequence of events (snowmelt followed by freezeback and another melt) and demonstrate its effect in reducing recharge in a multiyear, multilocation statistical analysis. This finding indicates that frozen ground plays a role the partitioning of precipitation between recharge and runoff, but the effect is sensitive to the magnitude and temporal sequence of precipitation events and temperature fluctuations. Understanding the complex relationships between snow, midwinter melt and freezeback events, frozen ground, and recharge is critical for predicting how climate change will affect groundwater resources in the future.

Water Retention Potential in Novel Terrestrial Ecosystems Restored on Post-Mine Sites: A Review

Many activities are conducted with the view of reducing CO2 emission from fossil fuels, but mining extraction will continue to be important for energy sources, mineral and metal ores, and the general economy. This activity has negative environmental consequences such as habitat loss, water scarcity, and soil degradation in novel ecosystems. Additionally, climate change, drought, and desertification accelerate important problems with water retention. From one point of view, identifying and conserving critical regions for ecological sustainability are issues of fundamental importance, but on the other hand, post-mine sites could provide additional carbon sinks and improve regional water retention (WR). This review paper analyses different studies focusing on the impact of the reclamation of mining sites on the water retention properties of soil. Water retention in reclaimed mining soil (RMS) increased considerably after various restoration efforts were implemented. The amount of water holding capacity in RMS was mostly affected by reclamation methods, soil properties, soil biota, restoration duration, and vegetation type. The major conclusions from the analysis were that (i) the bulk density of reclaimed mining soil ranges from 1.35 to 1.50 g/cm3 and decreases with restoration duration; (ii) Soil fauna increases soil water storage capacity and plant litter and earthworms convert litter to fecal pellets, which increases water field capacity; and (iii) water holding capacity increases with duration of reclaimed sites and type of plants, i.e., afforestation and tree communities have higher WR than younger grasslands. Therefore, identification of the suitable reclamation method, restoration duration, vegetation type, and soil fauna are important factors for increasing water retention capacity at a regional scale.

Temporal and spatial changes in soil organic carbon and soil inorganic carbon stocks in the semi-arid area of northeast China

Soil organic carbon (SOC) and soil inorganic carbon (SIC) has important effects on soil physical, chemical and biological properties. They play an important role in coordinating the relationship between soil water and air, increasing soil water holding capacity and improving plant productivity. In this study, a boosted regression trees (BRT) model was developed to map the spatial distribution carbon stocks in the semi-arid region of Northeast China in 1990 and 2015. During the two periods, 10-fold cross-validation technology was used to test the performance and uncertainty of BRT model. In order to construct the model, 9 environmental variables (derived from climate, topography and biology) and 173 (1990) and 223 (2015) topsoil (0–30 cm) samples were used. The comparison between estimated and observed data shows that the RMSE of SOC and SIC stocks were 0.53 kgm−2 and 0.19 kgm−2 in 1990, and 0.65 kgm−2 and 0.20 kgm−2 in 2015, respectively. Elevation, normalized difference vegetation index, mean annual precipitation and Landsat band 3 were identifies as critical environmental factors for simulating the spatial distribution of SOC, accounting for 76.6 % and 70.3 % of the total relative importance in 1990 and 2015, respectively. Mean annual precipitation, mean annual temperature and topographic wetness index were the critical environmental factors for simulating the spatial variation of SIC during the two periods. Land use change also played an important role in the spatial variability of SOC and SIC stocks. In the past 25 years, soil carbon stocks decreased from 6.2 kg m−2 in 1990 to 5.9 kg m−2 in 2015. The spatial distribution pattern of SOC was high in northeastern area and low in southwestern area during the two periods, while the spatial distribution pattern of SIC was opposite to that of SOC stocks. The mapped soil carbon stock distribution is fundamental to future study of soil carbon cycle and regional carbon balance in semi-arid regions.

Effect of long term application of super absorbent polymer on soil structure, soil enzyme activity, photosynthetic characteristics, water and nitrogen use of winter wheat.

Water scarcity and seasonal drought are major constraints on agricultural development globally. Super absorbent polymer (SAP) is a good amendment that can improve soil structure, increase soil water retention, and promote crop growth even with less soil moisture. We hypothesize that long term application of SAP has a better effect on soil organic carbon, soil enzyme activity, photosynthetic characteristics, yield, and water and nitrogen use than short term application. A long term field experiment with different application rates (0 (CK), 15 (L), 30 (M), 45 (H) kg ha-1) of SAP was conducted at the Yuzhou water conservation agriculture base of the Henan Academy of Agricultural Sciences from 2011 to 2019. The results indicate that applying SAP increases > 0.25 mm aggregates and decreased<0.25 mm aggregates in the soil after one year (2011) and 9 years (2019) of application. In addition, soil organic carbon, soil microbial biomass carbon, soil sucrase and cellulase activities, soil water consumption, water consumption, net photosynthetic rate (Pn), leaf water use efficiency (LWUE) of wheat and yield, all increased after SAP application. SAP also boosts water use efficiency and nitrogen use efficiency. Correlation analyses show that SAP promotes the growth of wheat, and improves the utilization rate of soil water and nutrients by improving the soil structure and increasing soil organic carbon and microbial enzyme activity. Based on our research, SAP treatment at a dosage of 45 kg ha-1 is most effective and is thus recommended.

Enhancing Soil Quality of Short Rotation Forest Operations Using Biochar and Manure

Biochar and manure may be used to enhance soil quality and productivity for sustainable agriculture and forestry operations. However, the response of surface and belowground wood decomposition (i.e., soil processes) and nutrient flux to soil amendments is unknown, and more site-specific information about soil property responses is also essential. In a split-plot design, the soil was amended with three rates of manure (whole plot; 0, 3, and 9 Mg ha−1) and three rates of biochar (split-plot; 0, 2.5, and 10 Mg ha−1). Soil physical properties, nutrients, and enzyme activities were evaluated in two years. In addition, wood stakes of three species (poplar, triploid Populus tomentosa Carr.; aspen, Populus tremuloides Michx.; and pine, Pinus taeda L.) were installed both horizontally on the soil surface and vertically in the mineral soil to serve as an index of soil abiotic and biotic changes. Wood stake mass loss, nitrogen (N), phosphorus (P), and potassium (K) flux were tested. The high rate of both manure and biochar increased soil water content by an average of 18%, but the increase in total soil P, K, organic carbon (C) content, and enzyme activities were restricted to single sample dates or soil depths. Wood stakes decomposed faster according to stake location (mineral &gt; surface) and species (two Populus &gt; pine). On average, soil amendments significantly increased the mass loss of surface and mineral stakes by 18% and 5%, respectively, and it also altered wood stake nutrient cycling. Overall, the decomposition of standard wood stakes can be a great indicator of soil quality changes, and 10 Mg ha−1 of biochar alone or combined with 9 Mg ha−1 of manure can be used for long-term carbon sequestration in plantations with similar soil conditions to the present study.