Maintain Soil Water Research Articles

Long-term alfalfa planting mediates the coupling of soil water and organic carbon storage in a semi-arid area of the Loess Plateau, China

The key to restoring arid and semi-arid ecosystems is maintaining soil water and organic carbon contents. Alfalfa (Medicago sativa L.) is a high-yield perennial forage crop and performs ecological functions as a drought-resistance leguminous herb. It has been widely planted for reconstruction of degraded soils in the Loess Plateau in northwestern China, but long-term planting may affect soil carbon–water coupling and lead to crop yield reduction. To maximize the benefits of reconstructed grassland, this study explored the couplings of soil water, organic carbon, and alfalfa productivity along a reconstruction chronosequence in a semi-arid area of the Loess Plateau. Space-for-time substitution approach was used to select different-aged stands of reconstructed grassland (1, 5, 7, 10, 15, 20, 30 years old). Alfalfa above-ground biomass (AGB), soil water storage (SWS), organic carbon storage (SOCS), and carbon–water coupling coordination degree (D) were measured in the 0–100 cm soil profile. Alfalfa AGB reached a peak in the 7th year, and the degradation began in the 10th year. Both SWS and SOCS varied nonlinearly with stand age. The greatest loss of SWS occurred in the 15th year (80–100 cm depth), whereas the largest increase of SOCS occurred in the 30th year (0–20 cm depth). There was a negative feedback relationship between AGB and SWS over the 30-year study period (Pearson r = −0.835, P = 0.098). AGB and SOCS initially showed a trade-off within the first 10 years (Pearson r = −0.7431, P = 0.2569), in contrast to their positive feedback in the 20–30th years (Pearson r = 0.9978, P = 0.0421). A decoupling between SWS and SOCS (D < 0.6) was observed after 12 years of alfalfa planting. For agricultural production, a greater supply of water and organic fertilizer is required from the 7th year of alfalfa planting, and reseeding may be needed around the 10th year to prolong the life of alfalfa community. Alfalfa should be planted for no more than 12 consecutive years in the study area for ecological protection.

Enhancing soil water stability and retention through plastic mulching under atypical climatic conditions on the Chinese loess plateau

Mulching is an agricultural practice that is extensively implemented worldwide to conserve water in soil to enhance agricultural production，and especially in the temperate continental monsoon climate regions. However, the mechanism controlling soil moisture evaporation, infiltration, and retention by mulching is unclear. We assess the impact of various mulching regimes on the soil–water equilibrium in the root zone of corn fields under atypical climate conditions(Excessive Precipitation) from 2020–2021 in five treatments: (1) ridges mulched with plastic film and furrows without mulching (RF), (2) conventional flat planting with full plastic mulching (FPM), (3) conventional flat planting with straw mulching (SM), (4) conventional flat planting with partial plastic mulching (PPM), and (5) conventional (control) flat planting with no mulching (CK). The HYDRUS-2D model was calibrated and validated using experimental data, to assess soil water content, water flux, and soil water balance within a two-dimensional soil profile. This model accurately replicated the root zone within the soil profile under all mulching scenarios, with numerical simulation outcomes closely aligning with observed measurements. Average R² values for FPM, PPM, RF, SM, and CK scenarios were 0.76, 0.75, 0.86, 0.85, and 0.77, respectively. During the 2020 and 2021 growing seasons, characterized by increased rainfall, plastic-covered treatments (FPM, PPM, RF) more efficiently reduced soil evaporation and enhanced soil-water retention. The combined soil drainage and storage changes for FPM, PPM, RF, and SM treatments exceeded those of CK by an average of 114.57, 64.93, 77.38, and 6.74 mm, respectively. FPM, PPM, and RF treatments had substantial water-retention capabilities during years of atypical climate. Notably, FPM ensured adequate water supply, facilitated deep soil water replenishment, and more effectively maintained soil water stability and retention. This underscores the pivotal regulatory function of mulching in mitigating the impacts of consecutive years of unusual climatic conditions.

Importance of stemflow to soil water replenishment in a montane forest of Popa Mountain Park, Myanmar

Stemflow (SF), rainwater that reach the ground by flowing down along the branches and trunk, is important in maintaining soil water content (SWC) and recharging groundwater in a forest. This study aims to investigate the importance of SF to soil water replenishment in a montane forest. Measurements of gross rainfall, SF at 9 trees, SWC at two different points for two soil depths and infiltration rates at the two points were carried out in Popa Mountain Park (PMP) in 2019. SF rates in PMP were high ranging from 4.0% to 18.8% of total gross rainfall. Mean SWC near the tree were 18.5% at 5 cm depth and 21.7% at 15 cm depth, respectively, while those outside the canopy area were 11.4% and 9.0%, respectively. SWC near the tree were significantly higher for both soil depths. Similarly, significant higher infiltration rate was found near the tree. Near the tree, infiltration rate exceeded the amounts of individual rain events helped to store more rainwater as SWC in deeper soil layers. In PMP, thus, vegetative cover particularly forested areas are expected to have hydrological advantages in restoring rainwater through a large amount of infiltrated SF into the soil.

Soybean yield response to managed depletion irrigation regimes in a Mid-South silt loam soil

Soybean irrigation experiments were conducted for five years (2013–2017) on silt loam soil in Jackson, TN, a sub-humid region with high and variable precipitation. The purpose of the experiment was to investigate managed depletion irrigation (MDI) regimes in soybean to obtain the highest yield with minimal water applied on high water-holding capacity soil. Another goal was to find the best use of soil matric potential sensors and water balances to achieve MDI goals. Irrigation supplemented rainfall at a rate of 1.27, 2.54, and 3.81 cm wk−1 starting from first bloom (R1), first pod (R3), and first seed (R5) stages and these treatments were compared against a rainfed control. The results lead to the recommendation that delaying irrigation to R5 in most years and R3 in dry years produced yields at the highest significance level. The connection between irrigation rate and yield fluctuates yearly, but generally, higher rates result in greater crop yields, necessitating a high irrigation rate and rainfall for managed depletion after initiation. The water balance method best emulated optimum MDI results when irrigation was delayed until the soil moisture depletion reached the management allowable depletion (MAD) and then was followed by irrigation that maintained soil water at the MAD level. The irrigation trigger points were initially lowered for matric potential sensors to avoid excess watering in early growth, transitioning to higher levels for optimal yield later in the R3 stage. These results may be applicable in other regions with high water holding capacity soil and moderate to high rainfall rates during the growing season.

Regulation of Na+/H+ antiport system and nitrogen metabolism by melatonin and endogenous hydrogen sulfide confers resilience to drought and salt stress

The present study was conducted with the purpose of examining the role of endogenous hydrogen sulfide (H2S) in melatonin (Mel)-induced regulation of tolerance mechanisms to drought stress and salinity. The drought stress was induced by maintaining soil water level at 40% and salinity was induced by applying 100 mM sodium chloride (NaCl). The results demonstrate an augmentation in the degree of activation of the antioxidant defense mechanisms in response to drought stress and salinity. However, a significant decline in the K+/Na+ ratio, accompanied by an elevation in reactive oxygen species, lipid peroxidation, and electrolyte leakage, was witnessed as well. A remarkable decrease in the level of hydration and content of chlorophyll was also observed under the imposed stress. The reported findings indicate that the administration of 30 µM Mel effectively regulated the activity of the Na+-H+ antiporter and H+-ATPase. This regulation ultimately led to an increase in K+ influx and a decline in Na+ efflux, resulting in an enhanced K+/Na+ ratio. Application of Mel also demonstrated an improvement in nitrogen metabolism, as well as the enzymatic and non-enzymatic antioxidant defense system. Additionally, Mel application caused a remarkable increase in the accumulation of osmolytes in drought stress and salinity -suffered plants. The synergistic effect of these characteristics resulted in the resilience of the Mel-supplemented plants to drought stress and salinity. However, application of hypotaurine (a scavenger of H2S) counteracted the beneficial impact of Mel which once again resulted in the same condition that was initially created by the imposed stress. These findings imply that Mel, in coordination with H2S was remarkable in inducing plant adaptive responses to drought stress and salinity.

Evidence of the very early effects of water deficit on cell division and expansion processes in tomato ovaries

Water deficit (WD) is known to reduce the final mass of tomato fruit. Despite the recorded positive relationship between final fruit mass and cell number, the latter being determined in the pre-anthesis period of ovary development, very few studies have investigated the effects of WD on ovary growth before anthesis. In this study, cell division and expansion in tomato ovaries (cv. H1311) were studied under two irrigation regimes: a control regime that maintained soil water content at field capacity and a WD regime with a 50% reduction in water supply compared to the control. The ovaries were sampled at 6 and 2 days before anthesis, at anthesis, at 2 and 5 days after anthesis, and at breaker stage. Effects of WD were already significant in the pre-anthesis period and the mesophyll layers contributed 96% of the final loss of fruit mass under WD. Overall, the results suggest that cell expansion was the predominant contributor to the loss of fruit mass, although cell number decreased at fruit scale. This was due to the relative contributions of the different layers to fruit cell number and mean cell volume, and to the specific patterns of development and response to WD occurring in each layer. This study provides important information on the regulation of fruit growth processes under WD and will help better predict the impact of it on fruit yield.

Bio-Waste Management in Razi University by production of Leaf Mulch for the first time in world

Mulch is a type of protective covering placed on or spread over the soil surface. Mulches can be organic or inorganic and are available in many forms. Plastic film, proprietary mulch fabric, pinebark, straw, wood chips, newspaper, bark, grass clippings and leaf litter are examples. The use of tree leaves as mulch is very important to maximize the use of bio waste and reduce the environmental impact of waste and it is seen as both economically and environmentally sensible. Therefore, Leaf Mulch was produced for the first time in the world at Razi University by designing devices and using the technical knowledge of researchers. The aim of Leaf Mulch production, in addition to the optimal use of bio waste, was to maintain soil water, strengthen soil, control weeds and balance in soil temperature.Keyword: Bio-Waste Management, Leaf-Mulch, Maintain soil water, Strengthen soil

Effect of Mulch Type and Application of Liquid Organic Fertilizer on Pumpkin Plants (Cucurbita moschata)

The production of pumpkin (Cucurbita moschata Durch) continues to increase. Optimize the production results, a special treatment is needed. The treatment can be in the form of cultivation techniques such as giving mulch or applying appropriate fertilizers. Research is located on Jl. Kaping Gajah No.45, Jatimulyo Village, Lowokwaru District, Malang City. Observation of parameters: observing the length of the tendrils, number of leaves, number of flowers, fruit weight, diversity of arthropods and intensity of disease in plants. The effect of using black silver plastic mulch (BSPM) is more influential on plant growth and yield than the treatment of black mulch and straw mulch. This is BSPM can suppress weed growth, maintain soil water balance, increase soil surface temperature, increase microorganism activity, keep soil loose, and stimulate root growth. The observations it can be seen that the use of liquid organic fertilizer (LOF) has more effect on plant growth and yield than without using LOF. This is because the use of LOF can stimulate the growth of production branches, and increase the formation of flowers and ovules, and reduce the fall of leaves, flowers and ovules. The use of BSPM and LOF will optimize the growth and yield of pumpkin plants. When use of BSPM and LOF, the soil will remain loose, the activity of soil microorganisms will increase, and the nutrients in the soil will also be maintained.

Ice-covered soil significantly minimizes topsoil water loss in a semi-arid farmland

Flood irrigation is widely used as the most common farmland irrigation measure worldwide. However, the larger water evaporation after flooding seriously affects soil water maintenance, especially in winter and spring in the semi-arid and arid regions of north China. Hence, how to more efficiently maintain soil water content (SWC) after flood irrigation has become an important issue. This study examined whether ice-covered soil after flood irrigation can maintain high soil moisture based on a field investigation. Our results showed that the increase of SWC due to flood irrigation was markedly higher in the topsoil than in the subsoil layer, and the soil water supplement mainly happened on the cultivated horizon. Compared with the fields with no flood irrigation, SWC of the topsoil in the fields with no ice cover and with ice cover after flood irrigation increased by 56.4% and 75.6%, respectively. Farmland with ice cover presented a higher SWC than that with no ice cover after flood irrigation, and SWC increased for the topsoil and subsoil layer by 12.25% and 8.56%, respectively. Our findings proved that ice cover significantly enhanced soil water replenishment efficiency of flood irrigation to the soil layer, and the ice-covered soil after flood irrigation maintain higher SWC for both soil layers. The ice-covered soil after winter flood irrigation contributes to a better soil water habitat for farming production as an effective agricultural water management measure.

The lagging movement of soil nitrate in comparison to that of soil water in the 500-cm soil profile

The combination of forage-crop rotation with conservation tillage has long been known to result in proven productivity and sustainability, but less information is available on the influence of long-term conservation tillage practices on the movement of soil water and residual nitrate at deep soil depths in forage-crop rotation systems. In this study, we measured the changes in soil water storage, residual soil nitrate accumulation and their relationship to study the long-term effects of tillage and mulching practices on regional nitrogen management in maize (Zea mays L.)-wheat (Triticum aestivum L.)-common vetch (Vicia sativa L., annual legume forage) rotation system. Soils were collected from the 500-cm soil profile at the harvest stage of the maize and common vetch after 19 years of continuous conventional tillage (T), conventional tillage followed by straw mulching (TS), no tillage (NT), and no tillage followed by straw mulching (NTS) on the Loess Plateau, China. The results showed that the NT practices increased soil water storage by 3.07% compared with the T practices in the maize field, mulching practices increased soil water storage by 3.47% compared with no mulching practices in the common vetch field, and the improvement effect was mainly concentrated in the deep soil layer (150–500 cm). When compared with no mulching, straw mulching practices increased residual soil nitrate accumulation by 51.20 kg ha−1 at shallow soil depths (0–120 cm) but decreased this accumulation by 206.09 kg ha−1 at deep soil depths (120–500 cm) in the maize field; however, straw mulching decreased nitrate accumulation by 16.25 kg ha−1 throughout the whole profile (0–500 cm) in the common vetch field. The NT practices decreased residual soil nitrate accumulation by 131.65 kg ha−1 compared with the T practices in the maize field but had no effects on the common vetch field in the 0–500-cm soil profile. Greater changes in soil residual nitrate accumulation appeared at depths of 200–500 cm than at other depths. Moreover, according to structural equation model, nitrite accumulation was limited by soil water storage. Soil nitrate peaked at deeper soil depths in the NT (90–120 cm) and TS (250–300 cm) treatments than in the T treatment (60–90 cm), whereas the NTS treatment resulted in no nitrate accumulation peak across the whole soil profile. Soil water recharge and depletion were deeper in the NT and TS treatments than in the T treatment, and this effect could limit the further leaching of soil nitrate into deep soil. The depth of soil water recharge was deeper than the depth of nitrate accumulation, and the vertical movement speed of soil residual nitrate was slower than that of soil water. Therefore, the downward movement of soil nitrate lagged behind that of soil water. Together, these results demonstrated that the NTS treatment exerted the strongest effect on maintaining soil water and decreasing residual nitrate accumulation at deep soil depths, which will be favorable for improving regional N management and assessing N budgets in agroecological systems on the Loess Plateau.

Integrated Duflow-Drainmod model for planning of water management operation in tidal lowland reclamation areas

The research objective was to develop field operational model to control water table level at reclaimed area of tidal lowland for food crop cultivation. DUFLOW computer model was used to evaluate the perfomance of water management network at secondary and tertiary levels, whereas DRAINMOD computer model is used to evaluate soil water status at tertiary block. Results of DUFLOW model simulation can be used to improve water management by passing the Secondary Irrigation Chanel (SPD) and Secondary Drainage Chanel (SDU) through tertiary channels, water gate installation of stop-log type and weir construction in Drainage Secondary Channel (SDU). The weir construction has function as long storage and capable to control or maintain soil water level in land not quickly drawdown. Drainmod simulation model is acceptable, this is indicated by the results of statistical analysis where the correlation coefficient value reaches 0.89. Analysis of DUFLOW-DRAINMOD computer model software showed mutually supportive results in which DUFLOW simulation results can provide water potential information in channel for supply purpose. This water level condition is an important part in DRAINMOD model because it has effect on soil water level dynamics as targeted on tertiary block as well as on capacity to applied drainage operation system.

Ground-Based Hyperspectral Remote Sensing for Estimating Water Stress in Tomato Growth in Sandy Loam and Silty Loam Soils.

Drought and water scarcity due to global warming, climate change, and social development have been the most death-defying threat to global agriculture production for the optimization of water and food security. Reflectance indices obtained by an Analytical Spectral Device (ASD) Spec 4 hyperspectral spectrometer from tomato growth in two soil texture types exposed to four water stress levels (70–100% FC, 60–70% FC, 50–60% FC, and 40–50% FC) was deployed to schedule irrigation and management of crops’ water stress. The treatments were replicated four times in a randomized complete block design (RCBD) in a 2 × 4 factorial experiment. Water stress treatments were monitored with Time Domain Reflectometer (TDR) every 12 h before and after irrigation to maintain soil water content at the desired (FC%). Soil electrical conductivity (Ec) was measured daily throughout the growth cycle of tomatoes in both soil types. Ec was revealing a strong correlation with water stress at R2 above 0.95 p < 0.001. Yield was measured at the end of the end of the growing season. The results revealed that yield had a high correlation with water stress at R2 = 0.9758 and 0.9816 p < 0.01 for sandy loam and silty loam soils, respectively. Leaf temperature (LT °C), relative leaf water content (RLWC), leaf chlorophyll content (LCC), Leaf area index (LAI), were measured at each growth stage at the same time spectral reflectance data were measured throughout the growth period. Spectral reflectance indices used were grouped into three: (1) greenness vegetative indices; (2) water overtone vegetation indices; (3) Photochemical Reflectance Index centered at 570 nm (PRI570), and normalized PRI (PRInorm). These reflectance indices were strongly correlated with all four water stress indicators and yield. The results revealed that NDVI, RDVI, WI, NDWI, NDWI1640, PRI570, and PRInorm were the most sensitive indices for estimating crop water stress at each growth stage in both sandy loam and silty loam soils at R2 above 0.35. This study recounts the depth of 858 to 1640 nm band absorption to water stress estimation, comparing it to other band depths to give an insight into the usefulness of ground-based hyperspectral reflectance indices for assessing crop water stress at different growth stages in different soil types.

Converting continuous cropping to rotation including subsoiling improves crop yield and prevents soil water deficit: A 12-yr in-situ study in the Loess Plateau, China

Water deficit and conventional production mode limited agriculture sustainable development on the Loess Plateau. Crop rotation and conservation tillage appears to serve as an effective strategy to optimize water resources distribution and utilization. From 2007–2019, a 12-yr in-situ experiment consisting of three cropping systems (winter wheat continuous cropping, WW; winter wheat-spring maize rotation, WM; spring maize continuous cropping, MM) and two tillage methods (conservation tillage, subsoiling, ST; conventional tillage, plowing, CT) were conducted in a semi-arid region, and grain yield, economic profit, water use, precipitation storage and loss, soil water balance were analyzed to explore the mechanism and potential of crop rotation and conservation tillage regulating soil water balance and increasing farmland productivity. Our results show that compared to WW, WM and MM significantly enhanced grain yield by 4358 and 8791 kg ha−1 in 2-yr rotation cycle, respectively. And ST increased grain yield after 3 cycles with 979 kg ha−1. WM and MM with ST significantly reduced precipitation loss (78 and 135 mm) during the fallow period, and increased WUE (6.5 and 10.8 kg ha−1 mm−1), compared to WW-CT. With the passage of time, soil water storage of WW and MM showed a decreasing trend in 100–200 and 0–100 cm layers compared to pre-experiment, with the rate of 18.1 and 13.6 mm per cycle. And ST could ease the downward trend, relative to CT. However, the WM-ST maintained soil water balance by regulating water use and precipitation storage, compared to the two continuous cropping systems. Additionally, correlation analysis showed that evapotranspiration was positive to soil water balance and we should consider crop water use when designing cropping system to prevent soil water deficit. Overall, the WM-ST achieved better soil water sustainability, on the basis of sacrificing grain yield partly (4646 kg ha−1 in 2-yr rotation cycle) compared to MM-ST, which perhaps more eco-friendly and sustainable agricultural technique to replace WW-CT in the Loess Plateau of China.

The role of biochar in alleviating soil drought stress in urban roadside greenery

Soil structure degradation is a major obstacle to vegetation growth in urban roadside greenery, particularly under drought conditions. Biochar application can improve soil structure and water retention; however, the mechanisms linking changes in soil aggregation with those in pore size distribution, and how they interactively influence plant growth remain unclear. In this study, we investigated the role of biochar in improving soil structure and water retention under drought stress in urban roadside greenery. In a field study, plots (2 m × 2 m) were established on roadside greenery in Suwon, Korea, in which 2.5% wt bochar was mixed with surface soil (<10 cm depth) (BCfield). During the eight-month experiment, drought conditions prolonged, and soil water content was continuously higher in BCfield than in CONfield. For a more mechanistic understanding, a 100-day greenhouse experiment was conducted on Rudbeckia hirta planted in sandy soil, either mixed with 4% wt biochar (BCgreenhouse) or without biochar (CONgreenhouse). Drought conditions were simulated by maintaining soil water content below 40% of the water-holding capacity. In the biochar-added soil, macro-aggregates (250–1000 μm) increased significantly after 60 days, probably due to biochar particles themselves acting as the same-sized aggregates. In addition, biochar can act as a binding agent for forming macro-aggregates, thereby preventing their disintegration into smaller-sized aggregates. Enhanced macro-aggregation in biochar-added soil, therefore, is a potential mechanism for the increased formation of meso-pores. These pores could retain more soil water for plant uptake, eventually increasing plant biomass and water use efficiency in the BCgreenhouse, by 39%, when compared with that in the CONgreenhouse under drought conditions. Our results indicate that biochar application is a potential management strategy for improving soil physical structure in urban roadside greenery, which would, in turn increase plant resistance and resilience to drought stress.

Enhanced maize yield and water-use efficiency via film mulched ridge–furrow tillage with straw incorporation in semiarid regions

ABSTRACT Film mulched ridge-furrow tillage (FMRF) with straw incorporation (S) can efficiently improve rain-fed maize yield and water use efficiency (WUE). The key mechanisms were investigated via a 3-year consecutive FMRF and S interactive experiments [CP (conventional planting, Control), CPS, FMRF, FMRFS] from 2014 to 2016. In comparison with CP, FMRFS increased the temperature by 1.8°C to 4.8°C and the soil water content of 0–200 cm soil profile (W200 ) by 98.0 mm to 106.7 mm from the seedling to tasseling stage, and decreased the temperature by 1.1°C to 3.7°C from flowering to maturity. The concentrations of soil organic carbon (SOC), soil total and available nitrogen, phosphorus and potassium (TN, TP, TK and AN, AP, AK) were also remarkable increased by 5.9% to 55.1% (P < 0.05) for FMRFS, respectively. FMRFS considerably mitigated the effects of the frequent water and heat stress and fertility deficit and led to a higher maize yield (27.0% to 40.0%), improved WUE (1.4-folds to 2.0-folds). The W200 , SOC, TN, TP, AN and AP significant contribute to maize yield. Therefore, FMRFS not only enhanced the soil fertility but also maintained soil water balance, thus causing a significant increase in maize yield and WUE.

Modelling the effects of climate change on transpiration and evaporation in natural and constructed grasslands in the semi-arid Loess Plateau, China

Investigating the effects of climate change on transpiration (T) and evaporation (E) in natural and constructed grasslands is of theoretical and practical significance for vegetation restoration and water resource management in the Loess Plateau, China. In this study, a two-year field experiment was conducted in one natural (Imperata cylindrica plot) and two constructed grasslands (Pennisetum giganteum and Medicago sativa plots) in the semi-arid Loess Plateau. Hydrus-1D models were then established and validated to simulate T and E processes under scenarios combining climate characteristics in both future periods and different hydrological years. The results showed that under all climate scenarios, T in the natural grassland, and P. giganteum and M. sativa plots ranged from 63.7–179.3, 126.8–245.5, and 96.9–243.1 mm, respectively, while E ranged from 90.6–131.9, 68.7–92.8, and 70.4–92.4 mm, respectively. Both T and E showed a decreasing trend in the future periods, exhibiting the highest values in wet years and the lowest values in dry years. The effects of climate change on T were greater than that on E in all three grasslands. Of the studied grasslands, T of M. sativa plot exhibited the strongest response, followed by that in the natural grassland and P. giganteum plot. However, E of the natural grassland responded to the strongest degree, followed by that of the P. giganteum and M. sativa plots. Precipitation during the growing-season was the most dominant climatic factor affecting T and E, and was positively linearly related with T and E (P < 0.01) in all three grasslands. The conversion thresholds of precipitation for T-E dominance were 435.8, 149.4, and 253.3 mm for the natural grassland, and P. giganteum and M. sativa plots, respectively. In constructed grasslands, more water was lost through T than through E; hence, the T/ET ratios were high (>0.55). In contrast, T was high in the natural grassland only in conditions of sufficient precipitation; hence, the T/ET ratio was relatively lower (around 0.5). Precipitation distribution strongly affected the soil water supply, and the natural grassland was more efficient in maintaining soil water than the constructed grasslands. Our study not only improves our understanding of the hydrological processes and water budget under different grass restoration measures, but also provides valuable guidelines for the management of water resources and the restoration of ecological environment in the Loess Plateau.

Soil aeration and relationship to inorganic nitrogen during aerobic cultivation of irrigated rice on a consolidated land parcel

Efficient use of irrigation water in Asia can be achieved through production of rice (Oryza sativa L.) on aerobic soil rather than submerged, anaerobic soil. Rice grown on aerobic soil is referred to as aerobic rice. The irrigation of aerobic rice without soil submergence might result in fluctuations and spatial variability in soil aeration, which can affect N transformations. We examined variability in soil aeration and inorganic N during the vegetative and ripening growth phases of aerobic rice grown on one 3.3-ha parcel with frequent irrigation using an overhead sprinkler to maintain soil water potential not less than −10 kPa without soil submergence. Water-filled pore space (WFPS) of soil ranged from 70–96% at 36 locations. The WFPS was inversely related to sand content (r = –0.66, P < 0.001). Soil ammonium-N was unrelated to WFPS, but nitrate-N was inversely related to WFPS (r = –0.84, P < 0.001) and directly related to sand content (r = 0.67, P < 0.001). The WFPS during production of aerobic rice favored nitrate accumulation at only some locations in the 3.3-ha parcel. Rice yield was inversely related to nitrate-N (P < 0.001). Nitrate-N, originating from both soil and fertilizer N, accumulated and exceeded ammonium-N at ≤77 % WFPS. Nitrate-N was small and < ammonium-N at>90 % WFPS, presumably due to N loss by denitrification. Precise irrigation of aerobic rice did not prevent spatial variability in soil aeration and nitrate, which was associated with inherent soil properties such as sand content.

Canopy Microclimate Modification with Reflective Mulches Under Oil Palm and Its Role to Soybean Growth

Land utilization under oil palm plantation is constrained by the condition of low light intensities. Modification of the microclimate through the use of reflective mulch, as a reflector, will increase its ability to reflect the land surface radiation under the tree stand. This modification may suitable for intercropping system between soybean and oil palm. The study aimed to determine the effect of microclimate modification, using reflective mulch, under the stand of oil palm, and to evaluate its effect on soybean productivity. The research was conducted at PTPN-VIII Cimarga Banten using a nested random design with two factors and three replications each. The first factor is the oil palm age, which consists of: (i) control (open land), (ii) 4 years, (iii) 5 years, and (iv) 8 years age of oil palm. The second factor is the reflective mulch, as a solar radiation reflector, which consists of three levels: (i) without mulch (control), (ii) inorganic reflective mulch/silver black plastic mulch, and (iii) organic reflective mulch/dried oil palm leaves. The application of inorganic and organic reflective mulch increased the distribution of reflected land surface radiation (59%-157%), reduced the soil temperature fluctuation (0.30C-1.20C), and maintained soil water content (45.2%-45.8%). An increased of plant growth rates (56%-86%), relative growth rates (16%-21%), and seed weight production per plant (74.8%-86.2%) also reported, as well as the reduction of the etiolation ratio (9.6%-12.5%). The use of organic and inorganic reflective mulches can improve the microclimate and increase the production of soybean under intercopping system with oil palm.

A Simple Method for Simulating Drought Effects on Plants.

Drought is expected to increase in frequency and severity in many regions in the future, so it is important to improve our understanding of how drought affects plant functional traits and ecological interactions. Imposing experimental water deficits is key to gaining this understanding, but has been hindered by logistic difficulties in maintaining consistently low water availability for plants. Here, we describe a simple method for applying soil water deficits to potted plants in glasshouse experiments. We modified an existing method (the “Snow and Tingey system”) in order to apply a gradual, moderate water deficit to 50 plant species of different life forms (grasses, vines, shrubs, trees). The method requires less maintenance and manual handling compared to other water deficit methods, so it can be used for extended periods of time and is relatively inexpensive to implement. With only a few modifications, it is possible to easily establish and maintain soil water deficits of differing intensity and duration, as well as to incorporate interacting stress factors. We tested this method by measuring physiological responses to an applied water deficit in a subset of 11 tree/shrub species with a wide range of drought tolerances and water-use strategies. For this subgroup of species, stomatal conductance was 2–17 times lower in droughted plants than controls, although only half of the species (5 out of 11) experienced midday leaf water potentials that exceeded their turgor loss (i.e., wilting) point. Leaf temperatures were up to 8°C higher in droughted plants than controls, indicating that droughted plants are at greater risk of thermal damage, relative to unstressed plants. The largest leaf temperature differences (between droughted and well-watered plants) were in species with high rates of water loss. Rapid osmotic adjustment was observed in leaves of five species when drought stress was combined with an experimental heatwave. These results highlight the potential value of further ecological and physiological experiments utilizing this simple water deficit method to study plant responses to drought stress.

Monitoring soil water content for decision supporting in agricultural water management based on critical threshold values adopted for Andosol in the temperate monsoon climate

Maintaining soil water content within the readily available range is optimum concerning crop production and water use. In this regard, the continuous monitoring of soil water content is a crucial element for identifying the key parameters for sustainable agricultural water management.In this study, volumetric soil water content (θv) was monitored and analyzed in a bare soil agricultural field (Sakaecho experimental field of Tokyo University of Agriculture and Technology). The field consisting of volcanic ash soils was monitored from June 2016 to September 2017 using capacitance sensor (CS). The optimal range of readily available water for plant uptake was defined as the range between field capacity and depletion level (θDep). These values were determined from the soil water potentials and θv values measured using pressure plate and soil cores, respectively.The 16-month period monitoring result revealed substantial temporal variability in θv in response to rainfall, evaporation and deep percolation. The monitored values of θv were above the θDep (0.307 cm3 cm−3 measured at suction (pF) value of 3.0) throughout the monitoring period for the 10–20 and 20–30 cm soil layers. In contrast, for the surface soil (0–10 cm), the θv fell below θDep for 27% of the monitoring period despite the high rainfall during those periods owing to high evaporation and deep percolation.The below θDep results for the surface soil suggests the need to conduct continuous θv monitoring, to support decision for planning efficient irrigation water management to avoid yield loss of shallow-rooted crops and deep-rooted crops at their earliest growth stages as well as quality reductions due to moisture stresses.