•140 kg N ha−1 applied at 2 times with 75 mm irrigation was recommended for maize.•240 kg N ha−1 applied at 3 times with 90 mm irrigation was recommended for wheat.•DPW response time to 30 m depth ...was 1 yr (135 mm irr.) and more than 2 yr (60 mm).•Nitrogen leaching loss flux decreased exponentially with soil depth.•Higher irrigation (≥105 mm) even with lower N could cause groundwater contamination.
Appropriate irrigation and nitrogen (N) management practices should be implemented to obtain high grain yields while considering the influence of water and N leaching on groundwater in the intensively cropped winter wheat (Triticum aestivum)-maize (Zea mays L.) rotation system. The calibrated RZWQM2 model was used to explore long-term (1984–2017) effects of irrigation and N fertilization on crop yield, water and nitrogen use efficiency, deep percolation water (DPW), N leaching loss (NLL), and their effects on deep soil layers (2−30 m) in this rotation system in the Jinghui Canal irrigation area of the Guanzhong Plain in China. Results showed that crop yields increased with increasing N rate. The critical N application rates of 140 and 240 kg N ha−1 coupled with 75 and 90 mm of irrigation for maize and wheat, respectively, resulted in high yields (7535 and 8977 kg ha−1), water use efficiency (2.22, 2.07 kg m-3), and nitrogen use efficiency (44.56, 40.78 kg kg−1). The simulated DPW values were 69 and 110 mm for maize and wheat, respectively, and NLL values were 25.36 and 25.47 kg ha−1. Crop yield and NLL for wheat were more sensitive to N application timing than maize yield and NLL, indicating that split N applications of two application times and three application times for maize and wheat, respectively, could be a more effective way of applying N fertilizer. DPW fluxes increased from 0.021-0.024 (varied over the 2−30 m depth) to 0.107-0.110 mm d−1 for irrigation ranging from 60 to 135 mm. The response times for DPW to be observed at the groundwater depth of 30 m could range from one year to more than two years, with DPW velocities of 0.034 and 0.077 m d−1 for 60 and 135 mm irrigation application amounts, respectively. NLL flux increased with added irrigation and N application rate, while decreasing exponentially with soil depth. Annual recharge of NO3-N to the groundwater (0.15–6.2 kg N ha−1) with lower irrigation amounts (60−90 mm) could be neglected, but higher irrigations (≥105 mm) even with lower N application rates could cause groundwater contamination. Therefore, comprehensively considering the effects of irrigation and fertilization practices on grain yields and groundwater could improve the sustainability of the agro-hydrological environment and agricultural production.
•Dynamics of N cycling was studied under spruce logging residues on a clear cut.•Stimulated N cycling processes increased N losses via leaching and N2O production.•Amount of residues affected soil N ...cycling and losses.
This study aimed to determine the effects of Norway spruce logging residues on the early-stage dynamics of N cycling processes on a clear cut and how this is related to N losses via leaching or nitrous oxide emissions. We compared N cycling processes in soil under spruce logging residues (fresh residues 40 kg m−2) and in corresponding soil without the residues for four growing seasons on a clear-cut in southern Finland. In addition, two other sites were studied in the same region six years after clear-cutting in plots with three different amounts of spruce logging residues (0, 10, 40 kg m−2). Logging residues strongly stimulated net nitrification within the first three months after the residue treatment, and this stimulation continued over the whole study period, although NO3-N concentrations in the soil decreased. Residues increased the pH, rate of net N mineralization and microbial C-to-N ratio. N2O production in the laboratory and fluxes in the field were both studied after four growing seasons. N2O production was higher in the humus layer under the residues and originated from both autotrophic nitrification and denitrification. N2O fluxes in the field were low but were also higher in the residue-containing plots. N concentrations in percolate water were monitored for four years at the same site. Logging residues increased NO3-N and NH4-N concentrations; the highest concentrations were found during the second and third years after clear-cutting. After that the concentrations of dissolved organic N increased. Both the percolate water study at this site and the N cycling studies at the two other sites six years after clear-cutting showed that the largest amount of residues resulted in the highest rates of net N mineralization and net nitrification and the highest concentrations of mineral N forms in the percolate water. The amount and decomposition stage of the logging residues as well as the development of ground vegetation may together determine the dynamics of soil N cycling processes and losses.
We analysed how logging residue (LR) piles of common tree species in Finland, Norway spruce (Picea abies (L.) H. Karst.), Scots pine (Pinus sylvestris L.) and silver birch (Betula pendula Roth), ...affect nitrogen (N) losses in forest soil after final felling. A Norway spruce dominated stand was clear-cut and followed by two experimental setups to study the nitrous oxide (N2O) emissions and leaching of carbon (C) and N. Experiments consisted of four treatments: tree species treatments consisting of 40 kg m−2 of LR and a control treatment without residues. The C losses were monitored as dissolved organic carbon (DOC), the N losses as ammonium (NH4-N), nitrate (NO3-N) and dissolved organic nitrogen (DON) fluxes and concentrations in soil percolation waters and the N2O emissions as fluxes from the forest soil to the atmosphere. In addition the soil temperatures, the molecular size distribution of the DOC from the soil percolation waters and the origin of the N2O production were determined. The LR piles lowered the soil temperatures and, especially those of birch, increased the concentrations of NO3-N in the soil percolation waters already 1 year after the establishment of the piles. The LR piles increased the NH4-N concentrations. The smallest molecular size fraction (<1 kD) of DOC predominated in all treatments. The N2O fluxes peaked under the piles during the second and third growing seasons; however, the inconsistent fluxes tended to be low. The production of N2O was driven by both nitrification and denitrification processes, the proportion depending on the tree species. Our results indicate that LR piles accelerate N losses 1 year after the clear-cutting, especially NO3-N, which predominates in the soil percolation waters under the birch residues, whereas spruce residues tend to stimulate N2O emissions longer. These results have implications for sustainable forest management practices and nutrition of regrowing vegetation.
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•Effects of logging residues of spruce, pine and birch were studied on a clear cut.•Logging residue piles accelerated C and N losses via leaching and N2O emissions.•Leaching losses of NO3-N increased most under birch residues.•Soil N2O fluxes remained low, although logging residues enhanced those losses.•Spruce residues tended to stimulate N2O emissions longer than other tree species.
•A. donax gave the highest yearly yield, N and P aboveground biomass content and the best performance for watertable protection.•M. x giganteus was the second best species after A. donax.•Across all ...species total nitrogen in percolation water decreased along the years to <2 mg L−1.•Across all species total phosphorus in percolation water decreased along the years to < 0.145 mg L−1.•The apparent N balance was negative for A. donax and positive for the other species.
Research has recently stressed the importance of combining renewable energy production with environmental protection. The aim of the present work was to find new perennial herbaceous plants adequate to figure out innovative energy cropping systems based on reduced input (no tillage, use of slurry and/or wastewater for nutrient supply) and with low environmental impact. Fourteen species were cultivated in growth boxes and fertilized with pellet manure (2010–2012) and digestate (2013). Research focused on comparison of biomass production, nitrogen (N) and phosphorus (P) accumulation in aboveground biomass and the quality of percolation water. Five species, C. indica, C. pseudocyperus, G. maxima, P. arundinacea and S. sylvaticus, did not survive more than one or two years of cultivation. A. donax had the highest biomass yield, increasing yearly (26.2, 62.8, 95.1 and 140.1 Mg ha−1, from 2010 to 2013, respectively) and significantly higher than all the other studied species. M. x giganteus production increased from the first (13.1 Mg ha−1) to the second year of cultivation and then remained stable (average 51.0 Mg ha−1); the other species showed increased productivity in the first years and then a dramatic drop in the last year. Again, A. donax had the highest nutrient accumulation in aboveground biomass, with mean yearly values of 631 kg N ha−1 and 83.2 kg P ha−1. The total N (TN) concentration in percolation water was higher in the first autumn-winter season, with a median close to 15 mg L−1 and great variability. Two years later, the median concentration fell to 2 mg L−1 and variability was considerably reduced. A. donax and M. giganteus turned out to be the best species in reducing nitrate N concentrations in percolation water. Concentrations of total P (TP) were two orders of magnitude lower than those of TN and showed higher and more variable values in 2012–2013 (from 0.060 to 0.145 mg L−1) than in 2010–2011 (from 0.025 to 0.034 mg L−1). The species did not significantly influence the TN and TP presence in the percolation water. Considering both biomass production and attitude to water table protection, A. donax gave the best results of all species studied.
Dissolved organic carbon (DOC) plays a key role in linking terrestrial and aquatic carbon cycles. Most of the work on soil and water DOC has been conducted in temperate watersheds. There is still a ...gap in knowledge on DOC dynamics within the tropics. This study assesses water extractable organic carbon (WEOC) in topsoils and describes the relationship between WEOC and land use/land cover (LULC), slope position, curvature and soil properties using linear regression in the Rukarara River Watershed (RRW) in Rwanda. The study analyzes DOC concentration in soil percolation water (pDOC) and describes its relationship with antecedent precipitation index (API) and mean antecedent temperature (MAT) within the watershed using quadratic regression. Generalized linear model (GLM) and linear mixed effect model (LME) with site and/or LULC random effects are used to predict WEOC within the watershed. WEOC concentrations range from 124 to 855 mgC/L in the study area. The highest WEOC concentrations were observed in natural forest, followed by tree plantations, tea plantations and croplands. t-test results did not reveal a significant difference between concentrations of WEOC in valleys, upper slopes, ridges, flat, concave and convex areas in the Rukarara River Watershed (RRW). Considering the relationship between WEOC and soil properties, significant positive correlation coefficients were 0.60, 0.53, 0.50, and 0.36 respectively for the total organic carbon (TOC), the total nitrogen (TN), the cation exchange capacity (CEC), and the aluminum (Al). The best predictor WEOC as a function of soil properties was the generalized linear model (GLM) and indicated soil TOC as the overarching soil factor of WEOC in the RRW by 71%. The pDOC concentration ranges between 0.34 and 10.03 mgC/L and its relationship with both API and MAT was concave upward. APIs explained 12 to 17% of the pDOC variation in the RRW whereas MATs explained 8 to 25%, the natural forest site showing the highest values and the cropland site the lowest values. This result means that a conversion from forest to cropland within the RRW could decrease DOC in both soils and in percolation water. Also, an increase of precipitation and temperature up to respective optima in the RRW, could increase DOC in percolation water and consequently in streams. This increase of instream DOC can impact the water quality of the Rukarara River and its streams, with implications for their ecological function. Strategies of land management and water resources should be enhanced to preserve soil and water quality in the RRW.
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•GLM of soil properties is the best predictor of soil WEOC.•Tea and tree plantations produce comparable soil WEOC.•Soil WEOC is relatively stable between slope positions, concave and convex areas.•TOC affects WEOC by 20 to 71% in the RRW.•pDOC is positively influenced by both antecedent precipitation and temperature.
(“Sources of soil dissolved organic carbon in a mixed agricultural and forested watershed in Rwanda”, 6)
This data article presents water extractable organic carbon (WEOC), percolation water ...dissolved organic carbon (pDOC), and mean antecedent precipitation indices (API) and mean antecedent temperature (MAT) data. The article also presents edaphic properties such soil texture elements, total organic carbon (TOC), total nitrogen (TN), cation exchange capacity (CEC), iron (Fe), and aluminum (Al). Additionally, the article presents topography attributes such including topographic position index (TPI) and curvature. All these data were used to analyze both WEOC and pDOC dynamics in the Rukarara River Watershed (RRW), Rwanda. WEOC and soil properties data were analyzed from sampled 52 soil composites samples collected during from October to December 2016 using 53 × 50 mm rings. Data of pDOC were analyzed from percolation water samples collected using a zero tension lysimeters on various dates during the period from Jun 2015 to Jun 2017. API and MAT data for various antecedent days were calculated on basis of rainfall and air temperature data recorded at three stations within the RRW using respectively tipping bucket rain gauges and sensors installed at three sites located representing the main land use land cover classes within the RRW.
The fate and transport of pretilachlor, one of the most widely used rice-paddy herbicides in Japan, were monitored in a rice paddy plot for 28 days after its application in the five study years. The ...effect of the percolation rate on herbicide loss was investigated. The concentration of pretilachlor in the paddy water was at its highest level within 2 days of application. The maximum concentration in percolated water was lower, and it was reached 1 or 2 days later than that in the paddy water. Almost all the pretilachlor loss was caused by percolation. The pretilachlor loss, as estimated from the amount that was applied and the cumulative percolation loss, ranged from 7.4 to 16.3%. In the five study years, the average percolation rate for the 7 days following application ranged from 11.5 to 29.3 mm/day. The pretilachlor loss increased proportionally with the percolation rate for 7 days following application.
We used the interdisciplinary model network REGFLUD to predict the actual mean nitrate concentration in percolation water at the scale of the Weser river basin (Germany) using an area--differentiated ...(100 m x 100 m) approach. REGFLUD combines the agro-economic model RAUMIS for estimating nitrogen surpluses and the hydrological models GROWA/DENUZ for assessing the nitrate leaching from the soil. The areas showing predicted nitrate concentrations in percolation water above the EU groundwater quality standard of 50 mg NO₃/l, have been identified as priority areas for implementing nitrogen reduction measures. For these “hot spot” areas a backward modelling approach was used to quantify the maximal permissible nitrogen surplus levels in agriculture to guarantee a mean long-term nitrate concentration in percolation water below 50 mg NO₃/l. Research work will directly support the implementation of the EU-Water Framework Directive in the Weser basin, e.g. by using the maximal permissible nitrogen surplus levels as a framework for the derivation of regionally adapted and hence effective nitrogen reduction measures.
Based on regional stakeholder preferences and planning guidelines as allocation criteria for SRC, this study aims at providing a transparent approach to evaluate multiple environmental effects and ...the regional significance of SRC systems. Using the example of two poplar SRC-systems (4-year rotation, 9-year rotation) the potential effects on ground water supply, wind erosion, and biodiversity aspects are evaluated in comparison to arable land for two selected municipalities in the district of Uelzen, Germany. Building on fuzzy membership functions and simple fuzzy-logic rules, the qualitative multi-criteria assessment is transparent and easily to adapt. This approach is transferable to other regions and spatial levels, since it derives from commonly available data and scientific evidence. Results show that implementation of SRC could provide multiple beneficial environmental effects, especially in areas with low landscape heterogeneity. The tools provided allow for a multi-criteria evaluation of environmental effects, and reveal the sensitivity to distinct allocation patterns. Physiographical conditions of the study area implicate a preference for mini-SRC systems. This is supported by smaller decline of annual deep percolation water compared to maxi-SRC. On average, decline in groundwater recharge of mini-SRC (92mm a
−1
) is comparable to irrigated arable land (80mm a
−1
), which is common practice in the study area. Currently, the utilization of beneficial environmental SRC effects is quite limited, since only 3 % of arable land is suitable for SRC implementation regarding farmers’ preferences for SRC allocation. Allocation preferences could however change substantially with increasing incentives for SRC, e.g., due to regional bioenergy schemes or “Greening” initiatives within the European Common Agricultural Policy, which is to be reformed by 2013.
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