Search Results (4)

Considerable amounts of irrigation water of vegetable crops grown in homogenous sandy soil profiles could be subjected to deep percolation water losses due to inappropriately designed surface or subsurface drip irrigation methods. This study aimed to investigate the combined influence of implementing clay soil layer in homogenous sandy soil profile of low-tech greenhouse ridges and using modified surface drip irrigation (M-DI) on soil moisture distribution and water productivity of tomatoes. In the greenhouse, a 7.5 cm thick clay soil layer was implemented 15 cm from the soil surface of each ridge as a hydraulic barrier. Three irrigation regimes (100%, 70% and 50% of ETo) were imposed with the M-DI on tomato plants and 100%ETo with surface drip irrigation (DI) as control. Regarding economic valuation, viability was preserved for the M-DI and DI methods. The outcome indicated that soil moisture spreads more horizontally than vertically on the sandy soil above the clay soil layer. The combined effect of the homogenous sandy soil profile amendment and full irrigation (100%ETo) with the M-DI irrigation method increased the tomato fruit yield by 64.5%. Furthermore, the combined influence enhanced water productivity by the M-DI to 54.7 kg/m³ compared to 32 kg/m³ by the DI. However, M-DI demonstrated dominance over DI regarding returns, yield, and profit. Economic-wise, the M-DI requires 50% less of the lateral pipelines needed by the DI in low-tech greenhouses. Adopting the M-DI with a hydraulic barrier can improve soil moisture, water productivity, yield, and returns for tomato crops in low-tech greenhouses under sandy soil conditions. Also, the M-DI with the hydraulic clay barriers was an economically viable investment compared to the DI without clay barriers for growing tomatoes in low-tech greenhouses. Full article

Previous studies have found that C turnover is bound to hotspots of microbial activity. The objective of this study was to analyze the effects of pure energy substrate (glucose), nutrient (mineral N or P) and combined substrate and nutrient (glucose + N, glucose + P, sterile DOC, artificial root exudate extract) additions to enzyme activity inside and outside hotspots as a proxy for microbial C turnover in a subsoil. By means of different substrate and nutrient additions, we tested how the limitations of our site were distributed on a small scale and depth-dependently to contribute to an increase in knowledge of subsoil mechanistics. The study site is a sandy Dystric Cambisol under an over 100-year-old beech forest stand in Lower Saxony, Germany. Forty-eight undisturbed soil samples from two depth increments (15–27 cm and 80–92 cm) of three profiles were sprayed homogeneously with easily available C, N and P sources to investigate the impacts of substrates and nutrients on three enzyme activities (acid phosphatase, β-glucosidase and N-acetylglucosaminidase) by using the soil zymography approach. Comparisons of upper and lower subsoils showed significantly fewer and smaller hotspots in the lower subsoil but with a high degree of spatial variation in comparison to the upper subsoil. Different patterns of enzyme distribution between upper and lower subsoil suggest microbial communities with a lower diversity are found in deeper soil regions of the site. Both substrate and nutrient additions stimulated enzyme activities significantly more outside the initial hotspots than within. Because of this, we conclude that microorganisms in the initial hotspots are less limited than in the surrounding bulk soil. Changes in enzyme activities owing to both substrate and nutrient addition were stronger in the lower subsoil than in the upper subsoil, showing differences in limitations and possible changes in microbial community structure with increasing depth. The results of our study emphasize the need to consider spatial factors in microbial turnover processes, especially in lower subsoil regions where stronger substrate and nutrient limitations occur. Full article

Capillary rise tests were conducted on soil columns containing of three layers of sandy soils with coarser over finer over coarser sandy soil to investigate the effect of the relatively finer soil interlayer. The capillary rise height, rate, and water distribution were observed in laboratory tests of four layered soil columns, with two homogeneous (without the interlayer) soil columns serving as the controls. The final maximum height of the capillary rise in the soil column with the interlayer was larger than that of the column without the interlayer when the interlayer was laid around the water entry value of the underlying soil. The water content was not continuous in the entire soil profile with the interlayer, and a small matric suction gap was observed in the relatively fine soil between the soil column with and without the interlayer. Full article

The water infiltration rules of five different homogeneously or heterogeneously-constructed soil samples were determined to select the best soil construction module for refuse dump reclamation in the opencast mines of the Shanxi-Shaanxi-Inner Mongolia energy circle. Five treatments, including three homogeneous soil samples consisting of sandy soil, Montmorillonite-enriched sandstone, and sand-Montmorillonite-enriched sandstone mixture, together with two heterogeneous soil samples composed of sandy soil + Montmorillonite-enriched sandstone + sandy soil and sandy soil + sandy − Montmorillonite-enriched sandstone mixture (7:3) + sandy soil. Three replicates of each treatment were prepared in the indoor pillars to measure the infiltration process by auto-recording geometry, to investigate the infiltration features of various soil configurations by testing their infiltration rate, cumulative infiltration capacity, wetting front migration, and profile soil content, and to evaluate the infiltration of newly constructed soil in the natural conditions of the research area. The experiment demonstrated that the addition of Montmorillonite-enriched sandstone into sandy soil significantly slowed down soil water infiltration, especially in the heterogeneous soils. Traditional models perfectly simulated the soil water infiltration in the three homogeneous soils in which soil infiltration capacity could be segmentally fitted by Kostiakov model and linear model, and wetting front could be fitted by a power function. Compared with the homogeneous soil samples, heterogeneous soil could reduce the direct surface runoff and deep percolation, and is an idealized structure for soil reconstruction in opencast coal mine dump. Full article