Differences In Soil Water Storage Research Articles

Modelling water/heat transfer and crop growth under film mulching condition in a seed–maize field

Film mulching has been widely applied in arid and semi–arid areas around the world. Current models simulating the process of water, heat, and crop growth generally neglect or simplify the role of film mulching in energy balance and water/heat exchange. In this study, CropSMPAC model was established based on previously developed model (CropSPAC, the soil water/heat transfer and crop growth model), by incorporating the influence of film mulching on energy budget and partition, sensible and latent heat fluxes of the soil surface, precipitation interception, and crop growth. The CropSMPAC model was calibrated and validated using experimental data from a seed–maize field located in arid Northwest China for the years 2017, 2018, and 2019. The experimental setup included two mulching treatments, i.e., full film mulching (M1) and no mulching (M0) along with three irrigation treatments, i.e., full irrigation (WF), medium irrigation (WM, 70%WF), low irrigation (WL, 40%WF). The results demonstrated that the model performed well in simulating the dynamics of field water, heat, and crop growth under various film mulching and irrigation conditions. The Nash-Sutcliffe efficiency coefficients for net radiation, soil heat flux, soil water storage (SWS), soil temperature (ST), leaf area index (LAI), aboveground dry biomass (ADB) were 0.57, 0.37, 0.79, 0.76, 0.95, 0.95, respectively. The relative errors for seed-maize yield, crop evapotranspiration (ET) were 9.38%, 9.10%, respectively. Furthermore, the model accurately reflected the differences in SWS and ST due to different mulching conditions (M1 and M0). The observed differences in SWS between M1 and M0 ranged from –30.6 to 32.9 mm, while the simulated differences ranged from –30.5 to 30.2 mm under various irrigation treatments. Similarly, the observed differences in ST between M1 and M0 were 1.8, 1.7, 1.0 and 1.4 °C at 10, 20, 40 and 80 cm soil depths, respectively, while the simulated differences were 2.3, 2.1, 1.7 and 0.8 °C under WF treatment. Additionally, the model effectively simulated the effects of film mulching on advancing the crop growth period and promoting LAI, ADB and yield. Overall, the model accurately captured the changes in energy fluxes, soil water, heat and crop growth caused by plastic film mulching, demonstrating that it is a useful tool for irrigation water management and crop production in crop land with film mulching.

Differences in soil water storage, consumption, and use efficiency of typical vegetation types and their responses to precipitation in the Loess Plateau, China

After massive afforestation, the Loess Plateau is facing the severe challenge of water shortages. Water use efficiency (WUE) is an important indicator of plant drought resistance, and high WUE is an important way to reconcile the contradiction between vegetation growth and soil water consumption (SWC). Different vegetation types significantly influence hydrological cycle process and WUE. In this study, the Biome-BGC model was used to simulate and analyze the soil water storage (SWS), SWC, and WUE of 3 typical vegetation types in the Loess Plateau from 2005 to 2020. The results showed that the order of SWS of different vegetation types from largest to smallest was grassland (GL, 81.82 mm/day), abandoned farmland (AF, 66.92 mm/day), and Robinia pseudoacacia forest (RP, 55.64 mm/day); SWC was RP (480.09 mm/year), GL (464.68 mm/year), and AF (421.79 mm/year); WUE was RP (2.37 gC/kgH2O), GL (1.10 gC/kgH2O), and AF (0.60 gC/kgH2O). GL showed a better water retention capacity. Precipitation recharge did not meet the full SWC of vegetation. In years of high vegetation growth, as well as in the dry season when water was scarce, both RP and GL showed varying degrees of water deficit. Correlation analysis revealed that a positive effect of precipitation on WUE has a threshold effect, and the thresholds range from approximately 15–50 mm/day for RP, 15–25 mm/day for GL, and no clear pattern for AF. Overall, in water-stressed areas, a large expansion of forest land should be reduced and GL should be increased. In seasons and areas where vegetation is growing vigorously or extremely arid, irrigation regarding precipitation thresholds should be carried out to improve the WUE of vegetation and promote the sustainable development of regional ecology.

Differences in Soil Water Storage, Water Consumption and Water Use Efficiency of Typical Vegetation Types on the Loess Plateau, China

Differences in Soil Water Storage, Water Consumption and Water Use Efficiency of Typical Vegetation Types on the Loess Plateau, China

Soil infiltration properties affected by typical plant communities on steep gully slopes on the Loess Plateau of China

Soil infiltration plays an important role in the processes of soil moisture, runoff generation, erosion, and nutrient movement under different climatic zones. Vegetation restoration may greatly affect soil infiltration process via altering soil and vegetation properties in arid and semi-arid region. However, few studies have been carried out to evaluate soil infiltration properties on steep gully slopes covered by typical plant communities in this region. This study was conducted to quantify the effects of typical plant communities on soil infiltration properties, and identify the main influencing factors on steep gully slopes of the Loess Plateau, China. Six typical plant communities of two shrubs (Caragana korshinskii and Hippophae rhamnoide) and four grasses (Artemisia sacrorum, Artemisia giraldii, Bothriochloa ischaemum, and Carex lanceolata) were selected to measure soil infiltration rate by a disc infiltrometer under four pressure heads of 0, −3, −6, and −12 cm. The results showed that soil infiltration properties of initial infiltration rate (IIR), steady infiltration (SIR), and hydraulic conductivity (Ks) were significantly affected by plant communities. IIR, SIR, and Ks varied from 1.54 to 0.27 mm min−1, 0.94 to 0.09 mm min−1, and 0.80 to 0.07 mm min−1 with the means of 0.78, 0.42, and 0.33 mm min−1. Plant communities of Artemisia sacrorum had the maximum IIR, SIR, and Ks, whereas Carex lanceolata had the minimum ones. Overall, IIR, SIR, and Ks of shrub communities were 14.7%, 4.9%, and 3.0% higher than those of grass communities. IIR, SIR, and Ks of shrub and grass communities with tap root systems were 1.90, 2.36, and 2.28 times greater than those with fibrous root systems. Variations in soil infiltration properties under different plant communities can be explained by the changes in soil texture, organic matter content, plant litter density, and root mass density. And plant litter and root were the main factors attributing to the changes in soil infiltration properties between different plant communities. The results are helpful to understand the differences in soil water storage, runoff, and erosion between different plant communities on steep gully slopes in arid and semi-arid regions.

Light Grazing Significantly Reduces Soil Water Storage in Alpine Grasslands on the Qinghai-Tibet Plateau

The degradation of alpine grasslands directly affects their ability to conserve water, but changes in soil water storage in grassland under different degrees of degradation are poorly understood. Here, we selected four grassland plots along a degradation gradient: no-degradation grassland (NG), lightly degraded grassland (LG), moderately degraded grassland (MG) and severely degraded grassland (SG). We then applied an automatic soil moisture monitoring system to study changes in soil water storage processes. Results revealed significant (p < 0.05) differences in soil water storage among NG, LG, MG and SG. Specifically, LG lost 35.9 mm of soil water storage compared with NG, while soil water storage in LG, MG and SG decreased by 24.5%, 32.1% and 36.7%, respectively. The shallow groundwater table, air temperature and grass litter were the key controlling factors of soil water storage in the grassland. Grazing and future global warming will significantly reduce soil water storage in alpine grasslands.

Effects of planting density on potato growth, yield, and water use efficiency during years with variable rainfall on the Loess Plateau, China

A 3-yr field study was conducted in semiarid areas of the Loess Plateau to investigate the effects of different planting densities on the soil water, potato growth, yield, and WUE during the normal year (2015), relatively dry year (2016), and relatively wet year (2017). The five potato planting densities were 3.75 × 104 (A, traditional local planting density as a control), 4.50 × 104 (B), 5.25 × 104 (C), 6.00 × 104 (D), and 6.75 × 104 plants ha–1 (E). During the three years, the differences in soil water storage among the five planting densities were significant in the early and middle potato growth stages, when the soil water storage levels in treatments B and C were 8.8 % and 10.8 % higher (P < 0.05) than those in A. Treatments B and C significantly (P < 0.05) increased the potato emergence rate by 12.5 % and 7.5 % to promote growth in the early and middle stages. The planting density had a decreasing parabolic relationship with the potato yield. After fitting a function to the three years of data, the highest tuber potato yield varied with the amount of rainfall and the optimum level was 5.12–5.58 × 104 plants ha−1. The WUE and rainwater use efficiency (RWUE) were significantly higher under B and C compared with A in the normal and relatively dry years. WUE and RWUE were significantly higher in B, C, and D compared with A in the relatively wet year. The optimum planting density with treatments B and C obtained higher net profits. Thus, the recommended optimum planting density should be 4.50–5.12 × 104 plants ha−1 in relatively dry years and 5.13–5.58 × 104 plants ha−1 in normal and relatively wet years to increase dryland potato production and water use efficiency in the semiarid regions of the Loess Plateau, China.

Thresholds for run‐off generation in a drained closed depression

AbstractHydrological threshold behaviour has been observed across hillslopes and catchments with varying characteristics. Few studies, however, have evaluated rainfall–run‐off response in areas dominated by agricultural land use and artificial subsurface drainage. Hydrograph analysis was used to identify distinct hydrological events over a 9‐year period and examine rainfall characteristics, dynamic water storage, and surface and subsurface run‐off generation in a drained and farmed closed depression in north‐eastern Indiana, USA. Results showed that both surface flow and subsurface tile flow displayed a threshold relationship with the sum of rainfall amount and soil moisture deficit (SMD). Neither surface flow nor subsurface tile flow was observed unless rainfall amount exceeded the SMD. Timing of subsurface tile flow relative to soil moisture response on the shoulder slope of the depression indicated that the formation and drainage of perched water tables on depression hillslopes were likely the main mechanism that produced subsurface connectivity. Surface flow generation was delayed compared with subsurface tile flow during rainfall events due to differences in soil water storage along depression hillslopes and run‐off generation mechanisms. These findings highlight the substantial impact of subsurface tile drainage on the hydrology of closed depressions; the bottom of the depression, the wettest area prior to drainage installation, becomes the driest part of the depression after installation of subsurface drainage. Rapid connectivity of localized subsurface saturation zones during rainfall events is also greatly enhanced because of subsurface drainage. Thus, less fill is required to generate substantial spill. Understanding hydrologic processes in drained and farmed closed depressions is a critical first step in developing improved water and nutrient management strategies in this landscape.

Cellulosic biofuel crops alter evapotranspiration and drainage fluxes: Direct quantification using automated equilibrium tension lysimeters

AbstractAn increasing number of crops are being considered as potential sources of biomass for both conventional (e.g., maize/corn) and cellulosic (e.g., switchgrass, miscanthus, and hybrid poplar) biofuels. Studies investigating the hydrologic characteristics of these crops are often conducted at either the field scale with a focus on evapotranspiration (ET) or at the plot scale where experiments generally rely on soil water storage dynamics and residual water balances. While this has led to many important insights into crop–soil water interactions under these crops, there does not appear to be any multiyear direct comparisons of the drainage fluxes under this range of biofuel crops. Furthermore, important advancements in drainage flux measurement technologies have yet to be applied to quantify hydrologic fluxes below a range of biofuel crops. Here, we use soil water content (SWC) probes and automated equilibrium tension lysimeters (AETL) to characterize detailed differences in soil water storage and drainage fluxes under conventional and cellulosic biofuel crops. The results of this study suggest that there are significant differences between subsurface water fluxes under some conventional and cellulosic biofuel crops, such as 75% greater average annual drainage and more rapid drainage accumulation under switchgrass relative to maize.

IDENTITY TEST OF MODELS GENERATED IN NEUTRON PROBE CALIBRATION IN LATOSOL CULTIVATED WITH COFFEE AND SIGNALGRASS

&lt;strong&gt;ABSTRACT: &lt;/strong&gt;The sustainability of agricultural production can be improved through the use of cover crops. The objective of this study was to evaluate the Model Identity Method in the verification of equality of linear regressions resulting from the calibration of a neutron probe for different layers, as a function of signalgrass management as a cover crop between rows of soil coffee crop in the Brazilian Central Cerrado. Aluminum tubes were installed to access the probe and two saturation basins were built in a coffee area, irrigated by a central pivot, in an Oxisol, with two management systems, T (Traditional with bare soil) and B (Signalgrass in the row). Samples were taken at depths of 0-0.20; 0.20-0.40; 0.40-0.60; and 0.60-0.80 m for the determination of physical and water properties and monitoring of soil drying; concomitant measurements were taken with the neutron probe in these layers. Two calibration curves were constructed for each layer, which were compared by the above method. It was observed that treatment B yielded differences in soil water storage in the 0.20-0.40 m layer, differing from treatment T. The statistical method allowed the observation of equality of regressions between treatments B and T at depths 0-0.20, 0.40-0.60, and 0.60-0.80 m; it also showed the need for different regression curves per layer, besides justifying the need for neutron probe calibration for each specific local condition.

Calibration of a non-invasive cosmic-ray probe for wide area snow water equivalent measurement

Abstract. Measuring snow water equivalent (SWE) is important for many hydrological purposes such as modelling and flood forecasting. Measurements of SWE are also crucial for agricultural production in areas where snowmelt runoff dominates spring soil water recharge. Typical methods for measuring SWE include point measurements (snow tubes) and large-scale measurements (remote sensing). We explored the potential of using the cosmic-ray soil moisture probe (CRP) to measure average SWE at a spatial scale between those provided by snow tubes and remote sensing. The CRP measures above-ground moderated neutron intensity within a radius of approximately 300 m. Using snow tubes, surveys were performed over two winters (2013/2014 and 2014/2015) in an area surrounding a CRP in an agricultural field in Saskatoon, Saskatchewan, Canada. The raw moderated neutron intensity counts were corrected for atmospheric pressure, water vapour, and temporal variability of incoming cosmic-ray flux. The mean SWE from manually measured snow surveys was adjusted for differences in soil water storage before snowfall between both winters because the CRP reading appeared to be affected by soil water below the snowpack. The SWE from the snow surveys was negatively correlated with the CRP-measured moderated neutron intensity, giving Pearson correlation coefficients of −0.90 (2013/2014) and −0.87 (2014/2015). A linear regression performed on the manually measured SWE and moderated neutron intensity counts for 2013/2014 yielded an r2 of 0.81. Linear regression lines from the 2013/2014 and 2014/2015 manually measured SWE and moderated neutron counts were similar; thus differences in antecedent soil water storage did not appear to affect the slope of the SWE vs. neutron relationship. The regression equation obtained from 2013/2014 was used to model SWE using the moderated neutron intensity data for 2014/2015. The CRP-estimated SWE for 2014/2015 was similar to that of the snow survey, with an root-mean-square error of 8.8 mm. The CRP-estimated SWE also compared well to estimates made using snow depths at meteorological sites near (&lt; 10 km) the CRP. Overall, the empirical equation presented provides acceptable estimates of average SWE using moderated neutron intensity measurements. Using a CRP to monitor SWE is attractive because it delivers a continuous reading, can be installed in remote locations, requires minimal labour, and provides a landscape-scale measurement footprint.

The relative role of soil type and tree cover on water storage and transmission in northern headwater catchments

AbstractSoil water storage and stable isotopes dynamics were investigated in dominant soil–vegetation assemblages of a wet northern headwater catchment (3.2 km2) with limited seasonality in precipitation. We determined the relative influence of soil and vegetation cover on storage and transmission processes. Forested and non‐forested sites were compared, on poorly drained histosols in riparian zones and freely draining podzols on steeper hillslopes. Results showed that soil properties exert a much stronger influence than vegetation on water storage dynamics and fluxes, both at the plot and catchment scale. This is mainly linked to the overall energy‐limited climate, restricting evaporation, in conjunction with high soil water storage capacities. Threshold behaviour in runoff responses at the catchment scale was associated with differences in soil water storage and transmission dynamics of different hydropedological units. Linear input–output relationships occurred when runoff was generated predominantly from the permanently wet riparian histosols, which show only small dynamic storage changes. In contrast, nonlinear runoff generation was related to transient periods of high soil wetness on the hillslopes. During drier conditions, more marked differences in soil water dynamics related to vegetation properties emerged, in terms of evaporation and impacts on temporarily increasing dynamic storage potential. Overall, our results suggest that soil type and their influence on runoff generation are dominant over vegetation effects in wet, northern headwater catchments with low seasonality in precipitation. Potential increase of subsurface storage by tree cover (e.g. for flood management) will therefore be spatially distributed throughout the landscape and limited to rare and extreme dry conditions. Copyright © 2014 John Wiley &amp; Sons, Ltd.

Regulation of soil moisture dynamics in agricultural fields using strips of native prairie vegetation

There is a growing interest in the use of native prairie vegetation to restore the hydrologic balance in agricultural watersheds. The objectives of this study were to investigate the effects of establishing strips of native prairie vegetation (SNPV) in agricultural fields (CROP) on soil water dynamics and assess the potential value of SNPV as an agricultural conservation practice to regulate soil water dynamics. Soil water storage (SWS) was monitored biweekly at four soil depth intervals (0–30, 30–60, 0–60, 0–100) during the growing seasons of 2007, 2008, 2009 and 2010 at the Neal Smith National Wildlife Refuge, Prairie City, Iowa. The influence of land cover (SNPV, CROP), topographic position (summit, sideslope footslope), season, and precipitation on SWS was analyzed. Results indicated that SWS was higher under prairie vegetation than CROP the year the SNPV was established (2007), while a reverse pattern was observed for the following three post-treatment years. More pronounced differences among land covers were observed in the first 30cm of soil. Overall, June–July had the highest SWS and August–September the lowest, but the trend varied within years. In 2009 and 2010, years of low and high precipitation, respectively, the differences in SWS among land covers were minimal and no statistical differences were observed. Overall, results indicate that the introduction of SNPV can contribute to the regulation of the water balance in agricultural watersheds by increasing water holding capacity, and hence, reducing runoff during high rainfall events.

沟垄全覆盖种植方式对旱地玉米生长及水分利用效率的影响

2008-2010年在渭北旱塬区,以沟不覆盖为对照(CK),研究垄上覆地膜沟内分别覆普通地膜(PP)、生物降解膜(PB)、玉米秸秆(PS)和液体地膜(PL)4种沟垄全覆盖种植模式对土壤水温、玉米生长、产量及水分利用效率的影响。结果表明,在玉米生长前期,PP、PB和PS处理可明显提高0-200 cm土壤蓄水量;生育中期,PS处理蓄水保墒效果最为显著;生育后期,各沟垄全覆盖处理与对照的土壤蓄水量无显著差异;整个生育期PL处理与CK的土壤蓄水量差异不显著。PP和PB处理3a玉米生育期5-25 cm平均土壤温度分别较CK增高1.6 ℃和1.3 ℃,PS处理降低1.9 ℃,而PL处理与CK无显著差异。PP和PB的增温保水效应使玉米株高、叶面积及地上生物量均高于CK;PS处理的降温效应促进玉米中后期生长,其株高、叶面积及地上生物量均高于CK;PL处理对玉米各生长指标影响不显著。与CK相比,PP、PB和PS处理3a平均的籽粒产量分别提高13.0%、13.8%和15.0%,水分利用效率分别提高9.8%、10.2%和11.6%。可见,垄覆地膜沟覆地膜、生物降解膜或秸秆的沟垄全覆盖种植可明显改善土壤的水温状况,促进玉米生长,从而显著提高作物产量和水分利用效率,对渭北旱塬区春玉米丰产栽培具有重要指导意义。;From 2008-2010, we conducted a field experiment in the Weibei Highlands to determine the effects of planting with ridge and furrow mulching on the soil water and temperature, and the maize growth, yield, and water use efficiency. Ridges were covered with plastic film in all treatments, while furrows were mulched with plastic film (PP), biodegradable film (PB), corn straw (PS), or liquid film (PL). In the control treatment (CK), ridges were covered with standard plastic film, while furrows received no mulching. The three-year trial showed that, during the early maize growth stage, the soil water storage (0-200 cm) was significantly higher with the PP, PB, and PS treatments compared with CK. The three-year average water storage increased by 14.1, 17.9, and 22.2 mm compared with CK. Our analysis of the vertical distribution of the soil water content in the 0-200 cm soil profile showed that the soil water content at the 0-20 cm and 100-200 cm depth were higher with PP, PB, and PS compared with CK. The effect of PS on water conservation was the highest during the middle growth stage, while the three-year average water storage was 16.9 mm higher with the PS treatment than CK. However, the soil storage with PP and PB was significantly lower than CK in 2008 and 2009. Compared with CK, the soil water content with PP and PB increased significantly at the 0-200 cm depth, whereas it decreased at the 80-180 cm depth. There were no significant differences among the mulching treatments during the later growth stage. Soil water storage was slightly higher with PL than CK, while there were no differences in soil water storage between the two treatments during the entire maize growing season. The three-year mean soil temperatures (5-25 cm) with the PP and PB treatments were 1.6 ℃ and 1.3 ℃ higher than CK, respectively, whereas the PS treatment was 1.9 ℃ lower than CK. However, there was no significant difference in the soil temperature with the PL treatment and CK during the maize growing season. The water retention and temperature-raising effects of the PP and PB treatments increased the plant height, leaf area, and aboveground biomass by 2.3% and 2.4%, 30.9% and 29.9%, and 15.5% and 13.9%, compared with CK, respectively, while the maize growing period was reduced by 5-6 d. The cooling effect of the PS treatment also increased the plant height, leaf area, and aboveground biomass by 7.0%, 34.6%, and 6.5% compared with CK, respectively, although the growing period was extended by 4-5 d. There was no difference between the maize growth indices of the PL treatment and CK during the entire maize growing period. PP, PB, and PS produced a higher maize yield and water use efficiency throughout the experimental period. Compared with CK, the PP, PB, and PS treatments increased the three-year mean maize yields by 13.0%, 13.8%, and 15.0%, with water use efficiency improvements of 9.8%, 10.2%, and 11.6%, respectively. Therefore, covering ridges with plastic film and mulching furrows with plastic film, biodegradable film, or corn straw, greatly improved the soil water and temperature status, promoted maize growth, and significantly increased the crop yield and water use efficiency. These results may have important implications for maize production in the Weibei Highlands, China.

The effect of long-term fertilization on soil water storage and water deficit in the Black Soil Zone in northeast China

Zou, W., Si, B., Han, X. and Jiang, H. 2012. The effect of long-term fertilization on soil water storage and water deficit in the Black Soil Zone in northeast China. Can. J. Soil Sci. 92: 439–448. The Black Soil Zone in northeast China is one of the most important areas of agricultural production in China and plays a crucial role in food supply. However, further improvement in crop yield hinges on effective management of soil water. There is a poor understanding of how different fertilization methods affect crop water use efficiency. The objective of this study was to examine the effect of different fertilization methods on soil water storage and deficit in Black soils. A long-term experiment was conducted at the National Field Research Station of Agro-ecosystems, at Hailun County, Heilongjiang province in northeastern China from 1999 to 2008. Three fertilizer treatments including no fertilizer (CK), inorganic fertilizer (NP) and inorganic fertilizer plus organic material (NPM) were tested. The results showed that soil water storage decreased in the order CK, NP, and NPM during the growing season and the differences in soil water storage in the active root zone (0–70 cm) and below the active root zone (70–130 cm) and soil water deficit were statistically significant among the three treatments. Due to the uneven temporal distribution of rainfall and crop water uptake, soil water content was very dynamic in all three treatments: The low soil water storage and resulting soil water deficit (defined as the monthly difference between potential evapotranspiration and soil available water storage) within the 0- to 70-cm soil profile were found in both June and July. Further, soil receiving NPM was more likely to have a soil water deficit, but less likely to have excessive water. A lower risk of excess water may result in deeper root penetration and increased water use at greater depth, and thus the water deficit under the NPM treatment may not be the limiting factor for crop production. Therefore, NPM seems a viable management practice for improving crop yields in the Black Soil Zone in northeast China, possibly due to higher soil organic carbon and nutrient supply and lower probability of excess water.

GOES Solar Radiation for Evapotranspiration Estimation and Streamflow Prediction

This study explores the value of incoming solar radiation estimates derived from geostationary operational environmental satellites (GOES) as an alternative solar radiation data source to historical solar radiation estimates for use in rainfall – runoff simulations. At 26 sites in the United States, the GOES-based solar radiation (\iR²=0.79) and ET\dp (R²=0.94) estimates agreed well with the ground-based estimates. There was a slight positive bias for the GOES-based solar radiation (5.4%) and potential evapotranspiration (8.7%) estimates compared to the ground-based estimates, with the strong and significant biases noted during the warm seasons. However, individual stations biases ranged from – 12 to 27%. Daily streamflow predictions made using National Weather Service River Forecast System’s Sacramento Soil Moisture Accounting rainfall.runoff model for four NOAA Distributed Model Intercomparison Project watersheds show that although notable peak storm flow differences occurred occasionally during extended drying periods, on average, the GOES-based potential evapotranspiration estimates slightly outperformed the simulations using ground-based data on an annual basis and were relatively insensitive to biases. However, on seasonal time scales, differences in soil water storage are evident and can result in numerous moderate differences in streamflow predictions.

Influence of various in situ rainwater harvesting methods on soil moisture and growth of Tamarix ramosissima in the semiarid loess region of China

The influence of different in situ rainwater harvesting and moisture conservation methods on soil moisture storage and growth of Tamarix ramosissima was studied in the semiarid loess region of China from 2002 to 2004. The treatments included control (T1), trench (T2), saucer covered by plastic film (T3), bare ridge and bare furrow (T4), plastic-covered ridge and bare furrow (T5), and plastic-covered ridge and gravel-covered furrow (T6). The results indicated that soil water storage for the T5 and T6 was significantly higher than the control. The T6 treatments produced the highest amount of soil water storage, 18–137 mm more than the controls at soil depth of 0–100 cm and 40–75 mm at soil depth of 100–200 cm. No significant differences in soil water storage were found between the T2, T3, T4 and the control treatments at soil depth of 0–100 cm, but soil water storage at soil depth of 100–200 cm was significantly higher for the T2, T3, T4 treatment than the control. Rainwater harvesting and moisture conservation treatments increased growth of T. ramosissima, tree height was significantly higher for the rainwater harvesting and moisture conservation treatments than the controls. Tree height, crown diameter and collar girth for the T6 treatments increased by 70, 57 and 79% as compared to the controls. No significant differences in crown diameter and collar girth were observed between T1, T2 and T3 or T4 and T5 treatments in some years. The effectiveness of the different treatments for the tree height, crown diameter and collar girth was in the order of T6, T5, T4, T3, T2 and T1.

SOIL WATER CONSERVATION, GROWTH, YIELD AND WATER USE EFFICIENCY OF SORGHUM AS AFFECTED BY LAND CONFIGURATION AND WOOD-SHAVINGS MULCH IN SEMI-ARID NORTHEAST NIGERIA

Water is perhaps the most important single factor that limits crop production in the semi-arid northeast of Nigeria. A four-year field experiment was therefore initiated in 1999 to evaluate the influence of land configuration practices with or without wood-shavings mulch on water conservation, yield and water use efficiency (WUE) of sorghum. The experimental treatments consisted of flat bed (FB), open ridging (OR), tied ridging (TR), FB + mulch (FBM), OR + mulch (ORM), and TR + mulch (TRM). Ridge heights were 15 to 20 cm and furrows were left open (for OR and ORM) or tied (for TR and TRM). Wood-shavings mulch was used at the rate of 5 t ha−1 in 1999, but this was increased to 10 t ha−1 in subsequent years to ensure adequate soil coverage. Differences in soil water storage at various sampling dates were significant only in some cases in each year, but trends were towards greater soil water storage in the mulched treatments than in the non-mulched treatments, irrespective of tillage method. Growth parameters (plant height and leaf area index) indicated significant differences between treatments on only some measurement dates in each year. Sorghum water use varied significantly between years and treatments. Seasonal water use was greater with FBM, ORM and TRM than with the FB treatment in all cropping seasons. Averaged over the four-year period, mean increases in grain yield relative to the FB treatment were 16 % for OR, 25 % for TR, 77 % for FBM, 50 % for ORM and 57 % for TRM. Pooled across the experimental years, the WUE (ET) of FB, OR, TR, FBM, ORM and TRM were 1.95, 2.12, 2.13, 2.74, 2.36 and 2.48 kg ha−1 mm−1 respectively. The corresponding WUE(R) values for these treatments were 1.26, 1.46, 1.56, 2.22, 1.88 and 1.97 kg ha−1 mm−1 respectively. It is concluded that combining the practice of flat bed cultivation with mulching may eliminate the need for ridging in increasing the productivity of sorghum grain in semi-arid northeast Nigeria.

Analysing the space–time distribution of soil water storage of a forest ecosystem using spatio-temporal kriging

In forest the soil water balance is strongly influenced by tree species composition. For example, differences in transpiration rate lead to differences in soil water storage (SWS) and differences in canopy interception cause differences in infiltration. To analyse the influence of tree species composition on SWS at the scale of a forest stand, we compare spatio-temporal patterns in vegetation and SWS. Geostatistical space–time models provide a probabilistic framework for mapping SWS from point observations. The accuracy of these models may be improved by incorporating knowledge about the process of evapotranspiration. In this paper we combine a physical-deterministic evapotranspiration model with space–time geostatistical interpolation to predict soil water storage in the upper 30 cm of soil (SWS 30) for a 0.5 ha plot in a mixed stand of Norway spruce ( Picea abies (L.) Karst.) and European beech ( Fagus sylvatica L.) in Kreisbach, Lower Austria. Soil water storage was measured at 198 locations by permanently installed wave guides. This was repeated 28 times, about every two weeks during the growing seasons of 2000 and 2001. Incorporation of a process-based model in space–time prediction of SWS 30 reduced the effect of precipitation on SWS 30 predictions prior to precipitation. Spatial patterns of SWS 30 between the permanent wilting point and field capacity depend on the precipitation and drying history, which is affected by vegetation. Early in the growing season spruce starts to transpire markedly, which is common for coniferous trees. During dry periods, spruce reduces transpiration earlier than beech. Overall beech transpires more than spruce during the growing season. The greater transpiration rates of beech are compensated for by greater soil water recharge after precipitation because less rainfall is intercepted. At low water contents near the permanent wilting point SWS 30 was spatially quite uniform. This was also the case at water contents nearfield capacity, probably because the soil physical parameters varied little. Space–time interpolation of SWS 30 and the prediction of soil water discharge and soil water recharge during periods of drying and rewetting demonstrate the important role of vegetation on the spatial patterns of SWS 30.

Characterisation of a windbreak system on the south coast of Western Australia. 3. Soil water and hydrology

This paper describes changes in soil water and ground water at various distances from a Pinus pinaster windbreak in south-western Australia. Soil water contents were measured by neutron moisture meter and time domain reflectometry at distances from a windbreak ranging from 1 to 20 tree heights (H). Within 3 H of the windbreak, soil water storage was reduced by 100–153 mm/1.8 m when compared to unsheltered conditions (20 H) over the 4 years of the experiment. Beyond 3 H, no significant differences in soil water storage were found which could be related to microclimate modification. Relationships between surface soil water storage (mm/0.4 m) at &lt;6�H and 12–24 H were 1 : 1 regardless of the technique used. Similarly, soil water depletion within the crop rootzone (mm/0.6 m) was similar at distances &gt;3 H. Reductions in the depth and duration of perched water levels occurred within 4 H of the windbreak. Despite this, the windbreaks had no effect on the regional ground-water levels.

Water use and drainage under phalaris, annual pasture, and crops on a duplex soil in Western Australia

Rising water tables in southern Western Australia are causing waterlogging and salinity problems. These issues are related to a lower level of water use by annual plants than by the native vegetation. Phalaris can use more water than annual pastures and crops because of deeper rooting characteristics and longer growing season. However, there is limited information on the water use of phalaris in the Western Australian environment. There is also very little information on water balances under annual crops and pastures outside the growing season. A field experiment was carried out on a duplex soil between March 1994 and March 1999. Annual rainfall varied between 321 and 572 mm. The study examined soil water content, deep drainage, and productivity of phalaris-based pasture, continuous annual pasture, annual pasture–wheat rotation, and a wheat–lupin rotation. The results showed that the phalaris-based pasture after the establishment year was 25% (1.9 t dry matter/ha) more productive than continuous annual pasture, with the main difference occurring in late spring–early summer. The phalaris-based pasture used, on average, 45 mm/year more water and reduced drainage below 1 m by 44 mm/year compared with the annual pastures and crops. Total drainage below 1 m was 30 mm under the phalaris-based pasture and 74 mm under annual pasture. The greater water use in the phalaris-based pasture occurred in late spring and early summer. Although differences in total biomass per year occurred between wheat in different rotations there was no difference in the soil water storage prior to the break of the season. There was also no difference in the soil water balance between any of the annual crops and pastures. Differences in soil water storage did occur in some years in October but disappeared by May the following year.