Intensive Cropland Research Articles

Model-Based Analysis of the Long-Term Effects of Fertilization Management on Cropland Soil Acidification.

Agricultural soil acidification in China is known to be caused by the over-application of nitrogen (N) fertilizers, but the long-term impacts of different fertilization practices on intensive cropland soil acidification are largely unknown. Here, we further developed the soil acidification model VSD+ for intensive agricultural systems and validated it against observed data from three long-term fertilization experiments in China. The model simulated well the changes in soil pH and base saturation over the last 20 years. The validated model was adopted to quantify the contribution of N and base cation (BC) fluxes to soil acidification. The net NO3- leaching and NO4+input accounted for 80% of the proton production under N application, whereas one-third of acid was produced by BC uptake when N was not applied. The simulated long-term (1990-2050) effects of different fertilizations on soil acidification showed that balanced N application combined with manure application avoids reduction of both soil pH and base saturation, while application of calcium nitrate and liming increases these two soil properties. Reducing NH4+ input and NO3- leaching by optimizing N management and increasing BC inputs by manure application thus already seem to be effective approaches to mitigating soil acidification in intensive cropland systems.

Solute and sediment export from Amazon forest and soybean headwater streams.

Intensive cropland agriculture commonly increases streamwater solute concentrations and export from small watersheds. In recent decades, the lowland tropics have become the world's largest and most important region of cropland expansion. Although the effects of intensive cropland agriculture on streamwater chemistry and watershed export have been widely studied in temperate regions, their effects in tropical regions are poorly understood. We sampled seven headwater streams draining watersheds in forest (n=3) or soybeans (n=4) to examine the effects of soybean cropping on stream solute concentrations and watershed export in a region of rapid soybean expansion in the Brazilian state of Mato Grosso. We measured stream flows and concentrations of NO3- , PO43- , SO42- , Cl- , NH4+ , Ca2+ , Mg2+ , Na+ , K+ , Al3+ , Fe3+ , and dissolved organic carbon (DOC) biweekly to monthly to determine solute export. We also measured stormflows and stormflow solute concentrations in a subset of watersheds (two forest, two soybean) during two/three storms, and solutes and δ18 O in groundwater, rainwater, and throughfall to characterize watershed flowpaths. Concentrations of all solutes except K+ varied seasonally in streamwater, but only Fe3+ concentrations differed between land uses. The highest streamwater and rainwater solute concentrations occurred during the peak season of wildfires in Mato Grosso, suggesting that regional changes in atmospheric composition and deposition influence seasonal stream solute concentrations. Despite no concentration differences between forest and soybean land uses, annual export of NH4+ , PO43- , Ca2+ , Fe3+ , Na+ , SO42- , DOC, and TSS were significantly higher from soybean than forest watersheds (5.6-fold mean increase). This increase largely reflected a 4.3-fold increase in water export from soybean watersheds. Despite this increase, total solute export per unit watershed area (i.e., yield) remained low for all watersheds (<1kg NO3- N·ha-1 ·yr-1 , <2.1kg NH4+ -N·ha-1 ·yr-1 , <0.2kg PO43- -P·ha-1 ·yr-1 , <1.5kg Ca2+ ·ha-1 ·yr-1 ). Responses of both streamflows and solute concentrations to crop agriculture appear to be controlled by high soil hydraulic conductivity, groundwater-dominated hydrologic flowpaths on deep soils, and the absence of nitrogen fertilization. To date, these factors have buffered streams from the large increases in solute concentrations that often accompany intensive croplands in other locations.

Mitigation of herbicide runoff as an ecosystem service from a constructed surface flow wetland

Ecosystem services provided by wetland systems presently play a pivotal role in intensive cropland as water purification from agricultural pollution. A field trial was conducted in 2014 to evaluate herbicide runoff reduction and retention using a 0.32 ha constructed surface flow wetland (CSFW) at the outlet of a 6 ha agricultural basin. To simulate an extreme pulse contamination, the CSFW was flooded with a runoff contaminated with metolachlor, and terbuthylazine and two other subsequent floods with pure water were applied 21 and 65 days later. Results show that the CSFW can reduce runoff concentration of metolachlor and terbuthylazine by a factor of 45–80 even in extreme flooding conditions. Herbicides retention in the CSFW was reversible, and the second and third floods mobilized 14–31 and 3.5–7.0% respectively, of the amount detected in the first flood. The CSFW performs a high buffer capacity for herbicides, capable to provide water purification service, protecting downstream surface water. Moreover, mitigation capacity of a CSFW for a heavy runoff from a 10 ha basin is 90% for every 50 m in length of a 15 m wide wetland. This confirms that the implementation of CSFWs in agro-systems can improve the sustainability of agricultural production.

Honey bee success predicted by landscape composition in Ohio, USA.

Foraging honey bees (Apis mellifera L.) can routinely travel as far as several kilometers from their hive in the process of collecting nectar and pollen from floral patches within the surrounding landscape. Since the availability of floral resources at the landscape scale is a function of landscape composition, apiculturists have long recognized that landscape composition is a critical determinant of honey bee colony success. Nevertheless, very few studies present quantitative data relating colony success metrics to local landscape composition. We employed a beekeeper survey in conjunction with GIS-based landscape analysis to model colony success as a function of landscape composition in the State of Ohio, USA, a region characterized by intensive cropland, urban development, deciduous forest, and grassland. We found that colony food accumulation and wax production were positively related to cropland and negatively related to forest and grassland, a pattern that may be driven by the abundance of dandelion and clovers in agricultural areas compared to forest or mature grassland. Colony food accumulation was also negatively correlated with urban land cover in sites dominated by urban and agricultural land use, which does not support the popular opinion that the urban environment is more favorable to honey bees than cropland.

Landscape cultivation alters δ³⁰Si signature in terrestrial ecosystems.

Despite increasing recognition of the relevance of biological cycling for Si cycling in ecosystems and for Si export from soils to fluvial systems, effects of human cultivation on the Si cycle are still relatively understudied. Here we examined stable Si isotope (δ30Si) signatures in soil water samples across a temperate land use gradient. We show that – independent of geological and climatological variation – there is a depletion in light isotopes in soil water of intensive croplands and managed grasslands relative to native forests. Furthermore, our data suggest a divergence in δ30Si signatures along the land use change gradient, highlighting the imprint of vegetation cover, human cultivation and intensity of disturbance on δ30Si patterns, on top of more conventionally acknowledged drivers (i.e. mineralogy and climate).

Effect of cactus pear cultivation after Mediterranean maquis on soil carbon stock, δ13C spatial distribution and root turnover

Mediterranean ecosystems are characterized by nearly complete replacement of natural vegetation by intensive croplands and orchards leading to strong soil degradation. Organic carbon is usually accumulated in soils under maquis leading to partial regeneration of fertility for future agricultural use. The aim of this work was to investigate the effect of land use change from maquis to agriculture on soil organic carbon (SOC) stock and its spatial distribution in a Mediterranean system. Three Mediterranean land use systems (seminatural vegetation, cactus pear crop and olive grove) were selected in Sicily and analysed for soil C stocks and their δ13C. Total SOC and δ13C were measured up to 75cm soil depth within and between the rows of cactus pear and olive grove and along a similar transect in maquis, in order to evaluate the distribution of new and old C derived from roots. The land use change from Mediterranean maquis (C3 plant) to cactus pear (CAM plant) lead to a SOC decrease of 65% after 28years of cultivation, and a further decrease for 14% after 7years after the change from cactus pear to olive grove (C3 plant). Considering these SOC losses as well as the periods after the land use changes we calculated the mean residence time (MRT) of soil organic matter. The MRT of C under Mediterranean maquis was about 142years, but was just 10years under cactus pear. Root biomass of cactus pear was used for a new approach to estimate root turnover. The root turnover rate of cactus decreased along the soil profile from 7.1% per year in 0–15cm to 3.7% in 60–75cm soil depth. Along the transect, the average of root turnover values was highest in the middle of the intra-row. Root turnover and C input were correlated with SOC stocks to evaluate C sequestration potential of soils depending on land use and managements. We conclude that the SOC under maquis is higher and has longer residence time compared to permanent agricultural crops like cactus pear and olives.

Effect of biochar on soil respiration in the maize growing season after 5 years of consecutive application

The effect of biochar on soil respiration (Rs) over one maize-growing season was studied after 5 years of consecutive application in an intensive cropland in the North China Plain. The experiment was carried out in randomly arranged plots with four treatments being evaluated. Three replications were conducted per treatment: a control plot without biochar addition (CK), biochar incorporated at 4.5 t ha–1 year–1 (BC4.5), biochar incorporated at 9.0 t ha–1 year–1 (BC9.0), and incorporated wheat straw (SR). The Rs was determined throughout the growing season of maize in 2012. Soil temperature and moisture were measured simultaneously at 5 cm depth. The results showed that the seasonal and diurnal variations of Rs in the four different treatments were approximately equal, and there was a positive correlation between Rs and soil temperature. The Rs values of treatments BC4.5 and BC9.0 were significantly lower than of SR but not CK. Significant correlations between Rs and soil temperature and soil moisture were observed. Soil temperature had a stronger effect on Rs than did soil moisture, and Rs was more sensitive to soil temperature in the biochar treatments than in the SR and CK treatments. The application of biochar and straw increased the soil active organic carbon content, but an obvious relationship between Rs and the soil active organic carbon content was not found.

Mapping and spatial analysis of the soybean agricultural frontier in Mato Grosso, Brazil, using remote sensing data

The main pioneer frontier considered by geographers is the Amazonian pioneer frontier. The occupation of the Brazilian territory has been carried out through successive economic cycles. Currently, the expansion of soybean crops in Amazonia is considered as the last economic cycle involving new migrations to still unexplored areas. Mapping this frontier is necessary in order to better understand its drivers and think about efficient land use policies to struggle its progress. In this paper, we propose an innovative methodology for mapping the agricultural frontier in the Amazonian state of Mato Grosso (Brazil) using satellite data acquired during the 2000–2006 period. We assume that the frontier evolves through successive land-use stages such as wildlands, non-croplands, extensive croplands and intensive croplands areas. The transitions between two stages can then be monitored through land-use change analysis. A particular emphasis is given on three land-use transitions named “deforestation”, “economic” and “intensification sub-frontiers”. In order to adapt this model for the use of remote sensing data, we defined (1) a relevant spatial scale corresponding to an agrarian locality, (2) relevant indices to qualify the land-use types and (3) rules applied on land-use types to define the frontier’s location. Our results highlight the dynamic of the agricultural frontier towards northern areas. We identified four main agricultural regions with different levels of agricultural intensification. We finally discuss these results with respect to governmental policies and economics for a better understanding of the frontier’s dynamic.

Wet deposition N and its runoff flow during wheat seasons in the Tai Lake Region, China

Interest in the study of wet deposition N continues to grow for its impact on terrestrial ecosystems. Assessing the contribution of wet deposition N to intensive croplands is significant for recommending N fertilizers and minimizing environmental hazards. NH 4 +–N, NO 3 −–N, and total N concentrations in wet deposition, seasonal deposition N fluxes, and N loads in event-based runoff were determined for four consecutive wheat seasons in the Tai Lake Region. Wet deposition N during wheat seasons ranges from 11 to 15 kg ha −1 (average, 13 kg ha −1), 61% of which is in the form of NH 4 +–N. NH 4 +–N concentrations range from 0.3 to 8.5 mg N L −1 (average, 1.7 mg N L −1), showing greater temporal variations than do those of NO 3 ––N, which range from 0.2 to 4 mg N L −1 (average, 0.8 mg N L −1). NH 4 +–N concentration in event-based runoff from wheat fields is much lower than that in rainfall, whereas that of NO 3 ––N is equal to or higher than that in rainfall. N loss through runoff reaches 1.8 kg N ha −1, accounting for 14% of wet deposition N. Results indicate that NH 4 +–N in wet deposition is prone to immobilization by the soil–crop system, whereas NO 3 ––N is relatively easily lost to runoff. The contribution of 11 kg ha −1 wet deposition N should be adjusted in fertilizer N recommendations for winter wheat cultivation in this region.

Organic Matter in Clay Density Fractions from Sandy Cropland Soils with Differing Land‐Use History

Land‐use history is often overlooked when assessing soil fertility of intensive cropland production systems. The unusually high organic carbon (OC) content of many sandy cropland soils in Northwestern Europe is unexpected given their general low clay content (3–8%) and organic matter (OM) input typical of cropland, but appears to be related to historical heathland land‐use. Clay fraction OM composition was compared between two groups of sandy cropland soils with (HC) or without (CC) a history of heathland/forest land‐use. Light (1.6–2.2 g cm−3) and heavy (&gt;2.2 g cm−3) clay fractions in HC soils were nearly twice as rich in OC (on average 199 g kg−1) compared with those of CC soils (on average 109 g kg−1). The hypothesized preferential presence of stable heathland derived OM in light soil fractions, was not supported by our data. Pyrolysis‐field ionization mass spectrometry of the clay fractions revealed a more decomposed character of OM in the CC soils and lasting long‐term influence of land‐use history on SOM composition. This could be concluded from higher proportions of lipids and sterols, a lower thermostability in the HC compared with the CC soils, and enrichment of alkylaromatics and heterocyclic N‐containing compounds in the latter. The density fractionation methodology separated organic‐mineral particles with similar OM loadings but lower proportions of sterols and medium to long‐chained lipids in the heavy compared with the light clay fraction. Given the very high clay OC loadings (6–16 mg C m−2) and low binding capacity of the quartz/kaolinite/mica dominated clays, we hypothesize that OM–OM interactions are involved as an OM stabilization mechanism. However, contrary to our hypothesis high clay OC loading (and hence thick OM layering) were found in all sandy croplands regardless of land‐use history or density fraction.

A Study on the Net Greenhouse Gas Emissions under Intensive High-yielding Cropland in North China-A Case Study of Winter Wheat-Summer Maize Rotation System in Huantai County

Abstract Utilizing the LCA matrix, we preliminarily analyzed whether wheat-maize rotation system was a carbon sink or a source based on long-term and large-scale straw return in Huantai county. The results indicated that the mode was a carbon source if we comprehensively considered agricultural materials production subsystem and farming subsystem together, with the quantity of net GHGs being -1075.71kgCO2e when producing 1 ton of wheat and maize. But if only farming system was considered, the averaged quantity of cropland carbon sequestration was +262.31 kgCO2e, which could offset the -222.99 kgCO2e carbon emission caused by fertilizes and agricultural machine. Therefore, through straw return and tillage system improvement, farming system might become the carbon sink in the future.

Characterizing the Spatial Patterns of Global Fertilizer Application and Manure Production

Agriculture has had a tremendous impact on soil nutrients around the world. In some regions, soil nutrients are depleted because of low initial soil fertility or excessive nutrient removals through intense land use relative to nutrient additions. In other regions, application of chemical fertilizers and manure has led to an accumulation of nutrients and subsequent water quality problems. Understanding the current level and spatial patterns of fertilizer and manure inputs would greatly improve the ability to identify areas that might be sensitive to aquatic eutrophication or to nutrient depletion. The authors calculated spatially explicit fertilizer inputs of nitrogen (N) and phosphorus (P) by fusing national-level statistics on fertilizer use with global maps of harvested area for 175 crops. They also calculated spatially explicit manure inputs of N and P by fusing global maps of animal density and international data on manure production and nutrient content. Significantly higher application rates were found for both fertilizers and manures in the Northern Hemisphere, with maxima centered on areas with intensive cropland and high densities of livestock. Furthermore, nutrient use is confined to a few major hot spots, with approximately 10% of the treated land receiving over 50% of the use of both fertilizers and manures. The authors’ new spatial disaggregation of the rich International Fertilizer Industry Association (IFA) fertilizer-use dataset will provide new and interesting avenues to explore the impact of anthropogenic activity on ecosystems at the global scale and may also have implications for policies designed to improve soil quality or reduce nutrient runoff.

Characterizing the Spatial Patterns of Global Fertilizer Application and Manure Production

Abstract Agriculture has had a tremendous impact on soil nutrients around the world. In some regions, soil nutrients are depleted because of low initial soil fertility or excessive nutrient removals through intense land use relative to nutrient additions. In other regions, application of chemical fertilizers and manure has led to an accumulation of nutrients and subsequent water quality problems. Understanding the current level and spatial patterns of fertilizer and manure inputs would greatly improve the ability to identify areas that might be sensitive to aquatic eutrophication or to nutrient depletion. The authors calculated spatially explicit fertilizer inputs of nitrogen (N) and phosphorus (P) by fusing national-level statistics on fertilizer use with global maps of harvested area for 175 crops. They also calculated spatially explicit manure inputs of N and P by fusing global maps of animal density and international data on manure production and nutrient content. Significantly higher application rates were found for both fertilizers and manures in the Northern Hemisphere, with maxima centered on areas with intensive cropland and high densities of livestock. Furthermore, nutrient use is confined to a few major hot spots, with approximately 10% of the treated land receiving over 50% of the use of both fertilizers and manures. The authors’ new spatial disaggregation of the rich International Fertilizer Industry Association (IFA) fertilizer-use dataset will provide new and interesting avenues to explore the impact of anthropogenic activity on ecosystems at the global scale and may also have implications for policies designed to improve soil quality or reduce nutrient runoff.

Quantifying spatiotemporal dynamics of agricultural landscapes using remotely sensed data and landscape metrics

This study focuses on the spatiotemporal dynamics of agricultural lands and differences in rapidly developing urban and declining rural counties in Iowa, USA between 1984 and 2000. The study presents an analysis of land-cover maps derived from Landsat TM and ETM+ satellite imagery and different landscape metrics using FRAGSTATS and IDRISI software. The study provides evidence of both loss of croplands and change in fragmentation between 1984 and 2000. Fragmentation in agriculture-dominated areas increased with the development of urban centres and diversification of land uses. Fragmentation of landscapes, including agricultural land, was found to be higher in the urbanized counties, but was stable or even declined over time in these counties. In contrast, in the context of remote rural areas, agricultural landscapes experienced rapid increase in fragmentation and farmland loss. The urban–rural gradient analysis used in this study showed that the highest fragmentation occurred on the city edges. These findings suggest that farmland fragmentation is a complex process associated with socio-economic trends at regional and local scales. In addition, socio-economic determinants of landscape fragmentation differ between areas with diverging development trajectories. Intensive cropland fragmentation in remote agricultural regions, detected by this research, should be further studied and its possible effects on both agricultural productivity and biodiversity should be carefully considered.