Effects Of Agricultural Management Practices Research Articles

Delineation of tile-drain networks using thermal and multispectral imagery—Implications for water quantity and quality differences from paired edge-of-field sites

As part of the Great Lakes Restoration Initiative, paired edge-of-field sites were established in high priority subwatersheds to assess the effectiveness of agricultural management practices. One pairing was in Black Creek, a tributary to the Maumee River and Lake Erie. These fields were paired because of similarity in soils, topography, and agricultural management. Following two years of baseline data collection from these fields, consistent differences in water quantity and quality were observed for tile networks draining the fields, despite these fields being adjacent and managed together. Consequently, it was hypothesized that differences in subsurface water movement, specifically tile-drain density and connectivity, were the source of the observed differences. Our objective was to map the tile-drain network using remote sensing methodology in order to improve the understanding of nutrient and water transport as well as management on these fields. A combination of multispectral and thermal imagery, collected in spring of 2017, was incorporated to delineate the tile-drain network within each field. This imagery led to locating a cracked tile, which provided a direct path for overland flow to enter the tile-drain system and suggested that a tile-drain segment under the road connected the two fields. A ground-penetrating radar survey verified multiple tile locations, including the tile segment under the road. The distribution of these tiles helps explain the difference in water quantity and quality in the two fields.

Evaluation of the RothC model as a prognostic tool for the prediction of SOC trends in response to management practices on arable land

RothC is an established model for predicting soil organic carbon (SOC) changes in response to environmental conditions and management. The model lacks algorithms for carbon input estimation and a differentiated consideration of carbon input sequestration from organic amendments commonly used in agriculture. Moreover, it does not consider the higher stability of below-ground crop residues in relation to above-ground crop residues.RothC was combined with two empirical approaches for quantifying carbon inputs from above- and below-ground crop residues and tested on 439 SOC data series from 36 arable long-term field experiments in Central and Northern Europe. Effects of carbon input quality on model fit were quantified with linear mixed models based on the analytical solution of RothC. Model parameters that describe the stability of incoming carbon were calibrated using a multi-site approach and Bayesian calibration. A second calibration study combined the determination of partitioning of incoming carbon into pools with different turnover rates and model responses to temperature and soil water content. With this calibration we showed that the contribution of above-ground residues to SOC is lower than when estimated with default RothC paramerization. We also show that the relative contribution from roots to SOC is higher than that from above-ground residues. Moreover, the degradability of organic amendments was highly variable between amendment categories and increased for all model configurations in the following order: farmyard manure < farmyard compost < sawdust < sewage sludge < peat. The proposed RothC partition coefficients for above-ground residues, roots and several commonly used organic amendments as estimated for this large data set should be useful for other studies in temperate climates. We also show that the analytical solution of RothC is closely related to the much simpler empirical humus balancing approaches used by farm advisory services. This provides opportunities to build bridges between the more process-oriented SOC models used in research and the well established instruments used by the farming community to assess the effects of agricultural management practices on SOC changes.

Total and available metal concentrations in soils from six long-term fertilization sites across China.

Approximately 19% of agricultural soils in China are contaminated by heavy metals. However, the effects of agricultural management practices on soil contamination are not well understood. Taking advantage of six long-term (23-34years) field sites across China, this study examined the effects of different agricultural fertilization treatments, including control (no fertilization), inorganic nitrogen, phosphorus and potassium fertilization (NPK), manure fertilization (M), and NPK plus manure fertilization (NPKM), on the total and available metal concentrations in soils. The results showed that after 23-34years of fertilization, the M and NPKM treatments significantly increased the total concentration of cadmium (Cd), copper (Cu), and zinc (Zn) in soils compared with the concentrations measured for the control and NPK treatments. In contrast, the fertilization treatments had almost no influence on soil lead (Pb) and nickel (Ni) concentrations. The results of analysis via diffusive gradients in thin films demonstrated that long-term sheep or cattle manure fertilization increased the available metals, especially Cd, Cu, and Zn, but long-term swine manure application decreased the available metals, except for Cu and Zn, in soils. Further analysis revealed that the manure source, soil pH level, and biogeochemical properties of metals affected the availability of Cd, Cu, Pb, Zn, and Ni in soils. Collectively, organic fertilizers had the potential to reduce metal uptake by crops, but caution should be taken to reduce metal concentrations in manure.

Effects of agricultural management practices on soil quality: A review of long-term experiments for Europe and China

In this paper we present effects of four paired agricultural management practices (organic matter (OM) addition versus no organic matter input, no-tillage (NT) versus conventional tillage, crop rotation versus monoculture, and organic agriculture versus conventional agriculture) on five key soil quality indicators, i.e., soil organic matter (SOM) content, pH, aggregate stability, earthworms (numbers) and crop yield. We have considered organic matter addition, no-tillage, crop rotation and organic agriculture as “promising practices”; no organic matter input, conventional tillage, monoculture and conventional farming were taken as the respective references or “standard practice” (baseline). Relative effects were analysed through indicator response ratio (RR) under each paired practice. For this we considered data of 30 long-term experiments collected from 13 case study sites in Europe and China as collated in the framework of the EU-China funded iSQAPER project. These were complemented with data from 42 long-term experiments across China and 402 observations of long-term trials published in the literature. Out of these, we only considered experiments covering at least five years. The results show that OM addition favourably affected all the indicators under consideration. The most favourable effect was reported on earthworm numbers, followed by yield, SOM content and soil aggregate stability. For pH, effects depended on soil type; OM input favourably affected the pH of acidic soils, whereas no clear trend was observed under NT. NT generally led to increased aggregate stability and greater SOM content in upper soil horizons. However, the magnitude of the relative effects varied, e.g. with soil texture. No-tillage practices enhanced earthworm populations, but not where herbicides or pesticides were applied to combat weeds and pests. Overall, in this review, yield slightly decreased under NT. Crop rotation had a positive effect on SOM content and yield; rotation with ley very positively influenced earthworms’ numbers. Overall, crop rotation had little impact on soil pH and aggregate stability − depending on the type of intercrop; alternatively, rotation of arable crops only resulted in adverse effects. A clear positive trend was observed for earthworm abundance under organic agriculture. Further, organic agriculture generally resulted in increased aggregate stability and greater SOM content. Overall, no clear trend was found for pH; a decrease in yield was observed under organic agriculture in this review.

Land use legacy regulates microbial community composition in transplanted Chernozems

Understanding how soil fertility and current practices affect microbial function in different soils is important for the development of sound management recommendations. However, interactions of the soil matrix with topography and climate obscure these interpretations. A long-term soil quality experiment was established in 1990 at Lethbridge, AB to examine the effects of agricultural management practices on different soils transplanted to a common location to normalize for climatic and topographic influences. Transplanted soils were continuously cropped to wheat with residues removed at harvest, with and without nitrogen (N) fertilizer (0 or 60 kg N ha−1). Phospholipid fatty acids (PLFA) profiling of whole communities and analysis of N-cycling functional genes in 10 of the transplanted soils sampled in 2012 revealed that soil origin and land use history had a dominant long-term impact on microbial abundance and community composition. Long-term N fertilizer application did not influence total microbial biomass, bacterial, and fungal abundance. The highest microbial biomass (ca. 25 nmol PLFA g−1 soil) was observed in more fertile (CC (cereal cultivated)) and RM (30 t ha−1 yr−1 manure) soils whereas the lowest biomass was found in transplanted sub-surface soils from B (6 nmol PLFA g−1 soil) and C horizons (8 nmol PLFA g−1 soil). Bacterial amoA, nirK and nirS community compositions were significantly influenced by N application. However, the degree of influence was mainly regulated by soil origin. Long-term N fertilization resulted in convergence of bacterial amoA community structure of CC and PL but not RM and DTF soils; archaeal amoA was not affected by N application. The reliance of the microbial community on inherent soil fertility was exacerbated by residue removal and was indicated by the strong influence of soil origin which reflected soil genesis and land use history. These findings reveal a persistent effect of soil legacy on soil microbial communities. Agricultural soil productivity can be enhanced by integrating soil history information into strategies for developing sustainable management practices.

Fallow replacement and alternative nitrogen management for reducing nitrate leaching in a semiarid region

Nitrate (NO3−) leaching into groundwater is a growing global concern for health, environmental, and economic reasons, yet little is known about the effects of agricultural management practices on the magnitude of leaching, especially in dryland semiarid regions. Groundwater nitrate–nitrogen (nitrate–N) concentrations above the drinking water standard of 10 mg L−1 are common in the Judith River Watershed (JRW) of semiarid central Montana. A 2-year study conducted on commercial farms in the JRW compared nitrate leaching rates across three alternative management practices (AMP: pea, controlled release urea, split application of N) and three grower standard practices (GSP: summer fallow, conventional urea, single application of urea). Crop biomass and soil were collected at ten sampling locations on each side of a management interface separating each AMP from its corresponding GSP. A nitrogen (N) mass balance approach was used to estimate the amount of nitrate leached annually. In 2013, less nitrate leached the year after the pea AMP (18 ± 2.5 kg N ha−1) than the year after the fallow GSP (54 ± 3.6 kg N ha−1), whereas the two AMP fertilizer treatments had no effect on nitrate leaching compared to GSPs. In 2014, leaching rates did not differ between each AMP and its corresponding GSP. The results suggest that replacing fallow with pea has the greatest potential to reduce nitrate leaching. Future leaching research should likely focus on practices that decrease deep percolation, such as fallow replacement with annual or perennial crops, more than on N fertilizer practices.

Effects of residue management and fertilizer application mode on soil organic carbon pools in an oasis cotton region.

To reveal the regulation mechanisms of agricultural management practices on soil organic carbon (SOC) pools and provide scientific basis for improving soil productivity and formulating agricultural fixed carbon and reducing discharge measures, we monitored the changes of SOC pools and organic carbon fractions in an oasis cotton field under different residue management and fertilizer application modes. A split-plot experimental design was used with differing residue management including residue incorporation (S) and residue removing (NS) in the main plots and differing fertilizer application modes including no fertilizer (CK), NPK fertilizer (NPK), organic manure (OM) and NPK fertilizer plus organic manure (NPK+OM) in the subplot. The results showed that fertilization and residue incorporation significantly increased SOC pool, soil organic carbon (CT), labile carbon (CL), microbial biomass carbon (CMB), water-soluble organic carbon (CWS), hot-water-soluble organic carbon (CHWS), accumulative amount of soil organic carbon mineralization (CTM) and carbon management index (CMI). The SOC pool was increased by 20.6% by residue incorporation compared to residue removing. SOC pools were increased by 7.8%, 29.5% and 37.7% in NPK, OM and NPK+OM treatments compared to CK, respectively. The contents of CT, CL, CMB, CWS and CHWS under different fertilization treatments were shown as NPK+OM>OM>NPK>CK. CTM was increased by 5.9% by residue incorporation compared to residue removing and CTM was increased by 32.7%, 59.5% and 97.3% in NPK, OM and NPK+OM treatments compared to CK, respectively. There was a significant correlation between CMI and CT, CMB, CL, CWS, CHWS, CTM, C pool and C sequestration. Therefore, we concluded that CMI is an important index for evaluating the effect of agricultural management practices on soil quality. In order to construct high-standard oasis farmland in arid region and develop cotton production, we should consider adopting reasonable agricultural management practices (i.e. combining residue incorporation with NPK fertilizer plus organic manure), which could increase the content of SOC, organic carbon fractions and soil fertility, promote soil carbon sequestration, and help the efficient use of agricultural resources and sustainable deve-lopment.

Crop rotation effects on yield, technological quality and yield stability of sugar beet after 45 trial years

Abstract Long-term field trials constitute an essential basis for research into the effects of agricultural management practices on yield and soil properties. The long-term field trial Etzdorf (Germany) was set up in 1970 and uses various crop rotations with sugar beets ( Beta vulgaris L., SB) to investigate the influence of increasing cropping concentrations (20 %–100 %) and decreasing cropping intervals (0–4 years) on the yield and quality parameters of SB. However, evaluation of the yield stability of SB in diverse crop rotations has not been conducted in this context so far. For this reason, the yield for the last 13 years of the trial (2002 until 2014) was subjected to such an evaluation. Besides cropping interval and cropping concentration, the crop rotations investigated also differed in terms of the complementary crops cultivated (winter wheat, Triticum aestivum L.; alfalfa, Medicago ssp.; potato, Solanum tuberosum L. and grain maize, Zea mays L.). Both SB root yield and white sugar yield increased with an increasing cropping interval or decreasing cropping concentration of SB in the crop rotation. In addition, a positive effect on root yield and white sugar yield was seen when integrating alfalfa, while cultivating SB after SB displayed the lowest root yield and white sugar yield. Sugar content was lowest in SB monoculture. In order to assess stability of white sugar yield, the coefficient of variation and ecovalence were calculated, and a linear regression analysis of the individual crop rotations’ annual yield was performed for the annual average of all crop rotations. When considering these three parameters, the crop rotations with a cropping interval of at least 2 years displayed higher yield stability, with simultaneously higher white sugar yield, than the crop rotations with a cropping interval of 0 and 1 year. By integrating alfalfa into the crop rotation, it was also possible to achieve above-average white sugar yield with high yield stability for a cropping interval of 1 year.

Coupling the short-term global forecast system weather data with a variable source area hydrologic model

Few current modeling tools are designed to predict short-term, high-risk runoff from hydrologically sensitive areas (HSAs) in watersheds. This study couples the Soil and Water Assessment Tool-Variable Source Area model with the Climate Forecast System Reanalysis model and the Global Forecast System-Model Output Statistics model short term weather forecast, to develop a HSA prediction tool designed to assist producers, landowners, and planners in identifying high-risk areas generating storm runoff and pollution. Short-term predictions for stream flow and soil moisture level were estimated in the South Fork of the Shenandoah river watershed. Daily volumetric flow forecasts were found to be satisfactory four days into the future, and distributed model predictions accurately captured sub-field scale HSAs. The model has the potential to provide valuable forecasts that can be used to improve the effectiveness of agricultural management practices and reduce the risk of non-point source pollution.

Distribution of soil carbon and grain yield of spring wheat under a permanent raised bed planting system in an arid area of northwest China

Soil organic carbon (SOC) plays a crucial role in improving soil properties and the C global cycle. Judicious tillage management can improve soil fertility and quality, and effectively reduce greenhouse gas emissions by enhancing soil carbon sequestration. An 8-year (2005–2012) field experiment was conducted in arid northwestern China to evaluate the effect of tillage practices on the distribution of total organic carbon (TOC), particulate organic carbon (POC) and microbial biomass carbon (SMBC) at 0–5, 5–10, 10–20, 20–40, 40–60 and 60–90cm soil depths, as well as TOC stratification, TOC stocks and grain yield of spring wheat (Triticum aestivum L.). Spring wheat was grown under three tillage systems: (1) permanent raised beds–zero tillage and ride culture with controlled traffic (PRB), (2) no-tillage planting on a flat field with controlled traffic (FB) and (3) traditional tillage −conventional tillage without residue retention (TT). A tillage effect was observed on TOC, POC and SMBC, which was significantly higher in the surface soil layer (0–10cm) in permanent raised beds (PRB) than in TT and FB. No differences in TOC or POC were encountered at 10–20, 20–40 and 60–90cm between treatments. Below 10cm, no differences in SMBC were observed between treatments, but TOC and POC contents at 40–60cm were significantly higher under TT than FB, with TT>PRB>FB. PRB had the highest TOC storage in the 0–90cm soil profile (75MgCha−1) followed by FB (74MgCha−1) and TT (69MgCha−1). Higher TOC stratification was observed under PRB and FB than under TT. Six years of PRB increased mean grain yield by 6% and 9% compared with TT and FB, respectively. We conclude that: (1) conservation tillage with controlled traffic (PRB and FB) increased TOC, POC and SMBC concentrations (0–10cm) and TOC stock, (2) SMBC is a sensitive indicator for reflecting the effect of agricultural management practices on TOC dynamics, and (3) PRB tillage could sustain wheat grain yields and increase carbon sequestration in arid northwestern China, such that PRB tillage is a more sustainable wheat cropping system than the TT system currently used by most farmers.

Toward optimal soil organic carbon sequestration with effects of agricultural management practices and climate change in Tai-Lake paddy soils of China

Understanding the impacts of climate change and agricultural management practices on soil organic carbon (SOC) dynamics is critical for implementing optimal farming practices and maintaining agricultural productivity. This study examines the influence of climatic variables and agricultural management on carbon sequestration potentials in Tai-Lake Paddy soils of China using the DeNitrification-DeComposition (DNDC, version 9.1) model, with a high-resolution soil database (1:50,000). Model simulations considered the effects of no-tillage, the application rates of manure, N fertilization, and crop residue, water management, and changes in temperature and precipitation. We found that the carbon sequestration potential in the top soils (0–30cm) for the 2.32Mha paddy soils of the Tai-Lake region varied from 4.71 to 44.31Tg C under the feasible management practices during the period of 2001–2019. The sequestration potential significantly increased with increasing application of N-fertilizer, manure, conservation tillage, and crop residues, with an annual average SOC changes ranged from 107 to 121kgCha−1yr−1, 159 to 326kgCha−1yr−1, 78 to 128kgCha−1yr−1, and 489 to 1005kgCha−1yr−1, respectively. Toward mitigating greenhouse emissions and N losses, no-tillage and increase of crop residue return to soils as well as manure application are recommended for agricultural practice in this region. Our analysis of climate impacts on SOC sequestration suggests that the rice paddies in this region will continue to be a carbon sink under future warming conditions. Specifically, with rising air temperature of 2.0°C and 4°C, the average annual SOC changes were 52 and 21kgCha−1yr−1, respectively.

Soil properties and not inputs control carbon : nitrogen : phosphorus ratios in cropped soils in the long term

Abstract. Stoichiometric approaches have been applied to understand the relationship between soil organic matter dynamics and biological nutrient transformations. However, very few studies have explicitly considered the effects of agricultural management practices on the soil C : N : P ratio. The aim of this study was to assess how different input types and rates would affect the C : N : P molar ratios of bulk soil, organic matter and microbial biomass in cropped soils in the long term. Thus, we analysed the C, N, and P inputs and budgets as well as soil properties in three long-term experiments established on different soil types: the Saria soil fertility trial (Burkina Faso), the Wagga Wagga rotation/stubble management/soil preparation trial (Australia), and the DOK (bio-Dynamic, bio-Organic, and “Konventionell”) cropping system trial (Switzerland). In each of these trials, there was a large range of C, N, and P inputs which had a strong impact on element concentrations in soils. However, although C : N : P ratios of the inputs were highly variable, they had only weak effects on soil C : N : P ratios. At Saria, a positive correlation was found between the N : P ratio of inputs and microbial biomass, while no relation was observed between the nutrient ratios of inputs and soil organic matter. At Wagga Wagga, the C : P ratio of inputs was significantly correlated to total soil C : P, N : P, and C : N ratios, but had no impact on the elemental composition of microbial biomass. In the DOK trial, a positive correlation was found between the C budget and the C to organic P ratio in soils, while the nutrient ratios of inputs were not related to those in the microbial biomass. We argue that these responses are due to differences in soil properties among sites. At Saria, the soil is dominated by quartz and some kaolinite, has a coarse texture, a fragile structure, and a low nutrient content. Thus, microorganisms feed on inputs (plant residues, manure). In contrast, the soil at Wagga Wagga contains illite and haematite, is richer in clay and nutrients, and has a stable structure. Thus, organic matter is protected from mineralization and can therefore accumulate, allowing microorganisms to feed on soil nutrients and to keep a constant C : N : P ratio. The DOK soil represents an intermediate situation, with high nutrient concentrations, but a rather fragile soil structure, where organic matter does not accumulate. We conclude that the study of C, N, and P ratios is important to understand the functioning of cropped soils in the long term, but that it must be coupled with a precise assessment of element inputs and budgets in the system and a good understanding of the ability of soils to stabilize C, N, and P compounds.

Long-term monitoring of soil management effects on runoff and soil erosion in sloping vineyards in Alto Monferrato (North–West Italy)

Long-term runoff and soil erosion data have been collected from differently managed field-scale vineyard plots within the “Tenuta Cannona Experimental Vine and Wine Center of Regione Piemonte”, located in the Alto Monferrato vine production area (NW Italy). The primary intent of the program was to evaluate the effects of agricultural management practices on the hydrologic, soil erosion, nutrient transport and soil compaction processes in vineyards. Field runoff data have been collected for every event since the year 2000 until now. Sediment and nutrient concentrations in water have been also monitored. Regarding soil properties and initial conditions, surveys have been carried out to investigate spatial and temporal variability of soil bulk density, soil saturated conductivity, soil water content, and penetration resistance. The Cannona Data Base (CDB) includes data for more than 300 runoff events and over 90 soil loss events; moreover, periodic measurements for soil physical characteristics are included for the three plots.Runoff and sediment yield showed high annual and seasonal variability and were strongly affected by the adoption of different soil management in the vineyard inter-rows, especially after some years of observation. Grass cover reduced runoff by at least 37%, in comparison with management by tillage, and average annual sediment yield ranged from 1.8Mgha−1year−1 to 20.7Mgha−1year−1, respectively for the “grass covered” and the “reduced tillage” vineyards. Furthermore, results showed the effect of the adopted soil management on soil properties. The Cannona Data base (CDB) can be accessed via a website (http://sustag.to.cnr.it/index.php/cannona-db) supported by the IMAMOTER-CNR.

Impact assessment of agricultural driven stressors on benthic macroinvertebrates using simulated data

Agricultural land use poses a significant threat to the ecological integrity of rivers in Europe. Particularly in the Mediterranean, water abstraction and nutrient application are anthropogenic pressures that have a significant impact on aquatic habitats and biodiversity. In this article, we assessed the effects of agricultural management practices on benthic macroinvertebrates in a large river basin of central Greece using simulated data based on the application of SWAT (Soil Water Assessment Tool) model. Physicochemical and hydrological output variables of the model were used as predictors of the ASPT (Average Score Per Taxon) metric based on a correlated component regression analysis (CCR) built on empirical data. The estimation of ASPT was performed for the wet and dry seasons within a 20-year period for a total of 47 subbasins under the baseline conditions and after implementing three management scenarios that reduced: a) irrigation water applied to crops by 30%, b) chemical fertilization applied to crops by 30% and c) both irrigation and fertilization by 30%. The results revealed that application of the reduced irrigation resulted to a slight increase of the simulated dissolved inorganic nitrogen concentration (DIN), which in turn decreased the mean ASPT in 21 of the 47 subbasins implying a negative effect on the macroinvertebrate communities. On the contrary, the reduction of fertilization as well as the combined scenario decreased both the simulated DIN and phosphate concentration causing an increase of the mean ASPT for a total of 40 of the 47 subbasins. Based on these results, we suggest that the best management option is a combined practice of deficit irrigation and fertilization reduction since it improved water quality, increased ASPT values and saved a considerable amount of water. Overall, this work demonstrates a simple methodology that can efficiently assess the effects of agricultural management practices on biotic indicators.

The NHDPlus dataset, watershed subdivision and SWAT model performance

The Soil and Water Assessment Tool (SWAT) has been developed to evaluate the effectiveness of agricultural management practices on watershed water quality. Many studies have indicated that watershed subdivision can affect the accuracy of model predictions. Most of them used the minimum drainage area (MDA) to delineate sub-watersheds, and varied the value of MDA depending on the size of the watershed being modelled. Instead of MDA, we use the National Hydrography Dataset Plus (NHDPlus)—an integration of the best features of the National Hydrography Dataset (NHD), Watershed Boundary Dataset (WBD), National Elevation Dataset (NED), and the National Land Cover Dataset (NLCD)—to delineate the watershed. The Kaskaskia River watershed in Illinois, USA, was selected to investigate the individual effects of sub-watershed and hydrologic response unit (HRU) delineations on predicted streamflow, total suspended sediment (TSS) and total nitrogen (TN) losses at two USGS gauges. In addition, an MDA of 3000 ha, and four levels of stream (the 2nd, 3rd, 4th and 5th order) were evaluated. Three levels of HRU threshold (5%, 10% and 15%) were used for each stream order model. The results show that stream order had little effect on predicted streamflow, but a great impact on TSS and TN losses, and the impact of HRU delineation became greater when a higher stream order was used to delineate the watershed. For higher stream order, fewer streams were recognized in SWAT simulations, which resulted in less sediment routing and channel processes, which, in turn, led to less deposition in the channels; thus high sediment losses were obtained at the watershed outlet. However, fewer channel processes led to less in-stream N processes; thus lower TN losses. Overall, the SWAT simulations performed the best when the 2nd stream order was used for delineations comparing with USGS observed data, followed by the 3rd stream order. Therefore, to fully depict the watershed characteristics to perform SWAT simulations, a stream order higher than 3rd order is not recommended for watershed delineation.Editor D. Koutsoyiannis; Associate editor C. Perrin

Effects of agricultural management practices on earthworm populations and crop yield: validation and application of a mechanistic modelling approach

Summary There is little consensus on how agriculture will meet future food demands sustainably. Soils and their biota play a crucial role by mediating ecosystem services that support agricultural productivity. However, a multitude of site‐specific environmental factors and management practices interact to affect the ability of soil biota to perform vital functions, confounding the interpretation of results from experimental approaches. Insights can be gained through models, which integrate the physiological, biological and ecological mechanisms underpinning soil functions. We present a powerful modelling approach for predicting how agricultural management practices (pesticide applications and tillage) affect soil functioning through earthworm populations. By combining energy budgets and individual‐based simulation models, and integrating key behavioural and ecological drivers, we accurately predict population responses to pesticide applications in different climatic conditions. We use the model to analyse the ecological consequences of different weed management practices. Our results demonstrate that an important link between agricultural management (herbicide applications and zero, reduced and conventional tillage) and earthworms is the maintenance of soil organic matter (SOM). We show how zero and reduced tillage practices can increase crop yields while preserving natural ecosystem functions. This demonstrates how management practices which aim to sustain agricultural productivity should account for their effects on earthworm populations, as their proliferation stimulates agricultural productivity. Synthesis and applications. Our results indicate that conventional tillage practices have longer term effects on soil biota than pesticide control, if the pesticide has a short dissipation time. The risk of earthworm populations becoming exposed to toxic pesticides will be reduced under dry soil conditions. Similarly, an increase in soil organic matter could increase the recovery rate of earthworm populations. However, effects are not necessarily additive and the impact of different management practices on earthworms depends on their timing and the prevailing environmental conditions. Our model can be used to determine which combinations of crop management practices and climatic conditions pose least overall risk to earthworm populations. Linking our model mechanistically to crop yield models would aid the optimization of crop management systems by exploring the trade‐off between different ecosystem services.

Mitigación de daños provocados por fauna silvestre en cultivos agrícolas en un bosque montano de Bolivia

Wildlife is often blamed for causing damage to human activities, including agricultural practices and the result may be a conflict between human interests and species conservation. A formal assessment of the magnitude of damage is necessary to adequately conduct management practices and an assessment of the efficiency of different management practices is necessary to enable managers to mitigate the conflict with rural people. This study was carried out to evaluate the effectiveness of agricultural management practices and controlled hunting in reducing damage to subsistence annual crops at the Cotapata National Park and Natural Area of Integrated Management. The design included seven fields with modified agricultural practices, four fields subjected to control hunting, and five fields held as controls. We registered cultivar type, density, frequency of visiting species to the field, crops lost to wildlife, species responsible for damage, and crop biomass. Most frequent species in the fields were Dasyprocta punctata and Dasypus novemcinctus. Hunted plots were visited 1.6 times more frequently than agriculturally managed plots. Crop lost to wildlife averaged 7.28% at agriculturally managed plots, 4.59% in plots subjected to hunting, and 27.61% in control plots. Species mainly responsible for damage were Pecari tajacu, D. punctata, and Sapajus apella. We concluded that both management strategies were effective to reduce damage by >50% as compared to unmanaged crop plots.

Cover crop effect on corn growth and yield as influenced by topography

The use of cover crops is reported to enhance ecosystem services, however their adoption by farmers has remained limited. A challenge to farmer uptake is high spatial and temporal variability in cover crop growth and performance. Since topography plays an important role in spatial processes that ultimately affect plant performance, it could be used to quantify cover crop spatial variability and cover crop contribution to a subsequent cash crop. We assessed the effects of topography and cover crop (red clover) biomass on corn yields. Hierarchical path analysis was used to identify direct and indirect relationships among topography, red clover biomass, and corn yield, while taking into account the effects of agricultural management practices, multiple years, and multiple experimental fields. We observed that topography contribute significantly to explaining the variability in both red clover biomass and corn yields. Higher red clover biomass was produced in flat areas, whereas higher corn yield was produced in areas with high curvature. Red clover biomass positively influenced corn yield, however, the magnitude of that effect varied both temporally and spatially. The effect of red clover on corn yields was significant only in the years with lowest precipitation; and its magnitude was more pronounced at summit and slope topographical positions. Therefore, a good cover crop stand will be most beneficial to subsequent corn crop at summit and slope positions. Accounting for variability in fields and years using a hierarchical model significantly improved analysis of the interactive relationships between topography, red clover, and corn; therefore we encouraged its use in agroecological research.

Evaluation of Soil Organic Carbon and Soil Moisture Content from Agricultural Fields in Mississippi

Independent observation of the effects of agricultural management practices on soil organic carbon (SOC) with soil moisture content (SMC) is essential to quantify their potential relationships for sustainable ecosystems. Soil water retention studies and soil carbon stocks have been mapped in some areas worldwide. However, few studies have been conducted in the southeastern US, particularly in Mississippi. The objectives of this research study were to collect soil samples from fields chosen to be representative of the watersheds they are contained within, analyze the soil samples for carbon content and soil moisture content, and evaluate the relationship between SOC and different parameters (land use, vertical distribution, temporal distribution, and soil moisture content). Field sites were chosen based on their compositional similarity shared with the watershed as a whole in the Town Creek watershed (TCW) and Upper Pearl River watershed (UPRW) in Mississippi. Monthly soil samples from different depths (6 inch, 12 inch, and 24 inch) were collected from crop, pasture, and forest field areas. Soil samples were analyzed using bench analysis, elemental analysis, and statistical analysis. This study was able to demonstrate the SOC distribution in the soil layers across all three land uses studied. It was also shown that there does seem to be an interactive effect of parameters such as land use type, vertical distribution, and time on carbon accretion within the soil. Results of this study also determined that the near surface (6-in) layer was found to contain significantly more carbon than either the 12 inch or 24 inch layers (p 0.01) across all field types. There was found to be a high degree of variability within the soil moisture data and correlation between SOC and SMC. It was found that carbon amount is not influenced by SMC but SMC could be influenced by SOC.

Bacterial community response to tillage and nutrient additions in a long-term wheat cropping experiment

The effects of agricultural management practices on bacterial community structure and function are not well defined, yet are of concern for long-term soil resilience. In this study, soil microbial biomass, bacterial community structure (determined by TRFLP), and function, (determined by enzyme assays and Biolog assays), and soil physicochemical properties were investigated in a wheat cropping system subjected to long-term tillage (20 years) and short-term nutrient addition treatments. Samples were taken over a full cropping cycle. Tillage, nutrient addition, and time all significantly affected bacterial community structure (rDNA and rRNA), which showed considerable shifts across the sampling period. Microbial biomass and Biolog profiles changed significantly with time, but were not affected by treatment. With regard to specific enzyme assays, there were significant main effects of treatment and time on glucosidase, phosphatase and phenol oxidase enzyme activity, while for cellobioside and peroxidase, treatment and time had significant interactive effects. For the hydrolases significant effects were observed between nutrient treatments, while for the oxidases they were observed between tillage treatments. Overall, however, we found little evidence of major detrimental long-term effects of tillage on the soil bacterial communities or their important functions in the dryland wheat system studied. The bacterial communities showed both long and short-term trajectories that could be disentangled with appropriate experimental design. Concerns over significant long-term detrimental impacts of tillage on the soil bacterial communities appear unfounded, at least under systems similar to those studied here.