Greenhouse gas emissions from croplands of China

China possesses cropland of 1.33 million km 2. Cultivation of the cropland not only altered the biogeochemical cycles of carbon (C) and nitrogen (N) in the agroecosystems but also affected global climate. The impacts of agroecosystems on global climate attribute to emissions of three greenhouse gases, namely carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O)

Expansion Potential for Irrigation within the Mississippi Delta Region

17.6 million acres, or 73 percent, of the Mississippi Delta Region is currently cropland and possesses the physical characteristics of slope, texture and soil type which are recommended for irrigation. Economic feasibility of expanding irrigation by flood, furrow and center pivot methods were examined under 24 scenarios representing two sets of crop prices, yield levels, production costs, opportunity costs and six crop rotations. Irrigation was economically feasible for 56 to 100 percent of the cropland across all scenarios. Approximately 88 percent of the cropland can be economically irrigated with flood or furrow in its present form, 8 percent yield highest net returns if furrow irrigated following land forming and 4 percent can be economically irrigated only with center pivot systems

Sensitivity of cropping patterns in Africa to transient climate change

The detailed analysis of current cropping areas in Africa presented here reveals significant climate sensitivities of cropland density and distribution across a variety of agro-ecosystems. Based on empirical climate-cropland relationships, cropland density responds positively to increases in precipitation in semi-arid and arid zones of the sub-tropics and warmer temperatures in higher elevations. As a result, marginal increases in seasonal precipitation lead to denser cropping areas in arid and semi-arid regions. Warmer temperatures, on the other hand, tend to decrease the probability of cropping in most parts of Africa (the opposite is true for increases in rainfall and decreases in temperatures relative to current conditions). Despite discrepancies and uncertainties in climate model output, the analysis suggests that cropland area in Africa is likely to decrease significantly in response to transient changes in climate. The continent is expected to have lost on average 4.1 percent of its cropland by 2039, and 18.4 percent is likely to have disappeared by the end of the century. In some regions of Africa the losses in cropland area are likely to occur at a much faster rate, with northern and eastern Africa losing up to 15 percent of their current cropland area within the next 30 years or so. Gains in cropland area in western and southern Africa due to projected increases in precipitation during the earlier portions of the century will be offset by losses later on. In conjunction with existing challenges in the agricultural sector in Africa, these findings demand sound policies to manage existing agricultural lands and the productivity of cropping systems.Climate Change,Crops&Crop Management Systems,Global Environment Facility,Common Property Resource Development,Rural Poverty Reduction

Effects of drainage ditches and stone bunds on topographical thresholds for gully head development in North Ethiopia

Gully erosion is an extreme process of land degradation operating in different regions of the world. A common way to quantify the susceptibility of land to gully incision is the use of topographical thresholds for different land use types. However, the impact of various management practices in cropland on these thresholds has not been studied to date, although land management may significantly affect runoff production, erosion processes and rates. Here, the impact of different land management practices on gully head development in cropland is studied based on a standardized procedure for topographical threshold analysis: s > kA− b, where s represents the slope gradient of the soil surface, A the drainage area at the gully head, b an exponent and k a coefficient reflecting the resistance of the land to gully head development. A case study area was chosen around Wanzaye, North Ethiopia, where three different cropland management practices were studied in 75 catchments: (i) the catchment-wide use of stone bunds on the contour, (ii) the use of slightly sloping drainage ditches (feses), and (iii) the combined use of stone bunds and feses. The lowest k-values (0.078–0.090) are found for catchments treated with feses, the highest k-values (0.198–0.205) are observed for stone bund catchments, and medium k-values (0.092–0.099) are found for mixed catchments. This finding implies that catchments with the exclusive use of drainage ditches are the most vulnerable to gully head development compared with mixed catchments and stone bund catchments. However, on-site sheet and rill erosion rates are reduced by feses as they lower the gradient of the overland flow lines. Three trends in cropland management around Wanzaye and the wider region are observed: (i) feses are exclusively made on rather steep slopes where small drainage areas lead to the rapid development of gully heads; (ii) stone bunds are constructed on both steeper and gentle sloping cropland; and (iii) larger and gently sloping catchments seem to be most suitable for the combined use of drainage ditches and stone bunds

Global patterns of cropland use intensity

This study presents a global scale analysis of cropping intensity, crop duration and fallow land extent computed by using the global dataset on monthly irrigated and rainfed crop areas MIRCA2000. MIRCA2000 was mainly derived from census data and crop calendars from literature. Global cropland extent was 16 million km2 around the year 2000 of which 4.4 million km2 (28%) was fallow, resulting in an average cropping intensity of 0.82 for total cropland extent and of 1.13 when excluding fallow land. The lowest cropping intensities related to total cropland extent were found for Southern Africa (0.45), Central America (0.49) and Middle Africa (0.54), while highest cropping intensities were computed for Eastern Asia (1.04) and Southern Asia (1.0). In remote or arid regions where shifting cultivation is practiced, fallow periods last 3–10 years or even longer. In contrast, crops are harvested two or more times per year in highly populated, often irrigated tropical or subtropical lowlands where multi-cropping systems are common. This indicates that intensification of agricultural land use is a strategy that may be able to significantly improve global food security. There exist large uncertainties regarding extent of cropland, harvested crop area and therefore cropping intensity at larger scales. Satellite imagery and remote sensing techniques provide opportunities for decreasing these uncertainties and to improve the MIRCA2000 inventory

The Role of Irrigation in Determining the Global Land Use Impacts of Biofuels

In recent years there has been a flurry of activity aimed at evaluating the land use consequences of biofuels programs and the associated carbon releases. In this paper we argue that these studies have tended to underestimate the ensuing land use change, because they have ignored the role of irrigation, and associated constraints on cropland expansion. In this paper, we develop a new general equilibrium model which distinguishes irrigated and rainfed cropping industries at a global scale. Using the new model we evaluate the implications of land use change due to US ethanol programs, in the context of short run constraints on the expansion of irrigated cropland. Since irrigated area tends to offer a higher yield than its rainfed counterpart, this provides an upper bound on the change in cropland following biofuel expansion. We find that the biofuel-induced expansion in global cropland cover is about 16 percent larger when the irrigation constraint is imposed. This translates into a 21 percent increase in land use emissions due to US ethanol production. This estimate represents an upper bound, since irrigated area can be expanded over the medium run in many places around the world.Land Economics/Use, Resource /Energy Economics and Policy,

COUNTY LEVEL TAXABLE AGRICULTURAL LAND VALUES IN NORTH DAKOTA: COMPARING THE GROSS REVENUE APPROACH WITH VALUES BASED ON RENTAL VALUES

Land values calculated with the current North Dakota agricultural land valuation model were compared with values calculated by capitalizing the average cash rent for each county. Results showed there was a significant difference in cropland values, but there was no significant difference in non-cropland values. Land values for the 2000, 2001, and 2002 assessments were compared.land valuation model, property taxes, North Dakota, Land Economics/Use,

RESULTS OF THE NORTH DAKOTA LAND VALUATION MODEL FOR THE 2006 AGRICULTURAL REAL ESTATE ASSESSMENT

This report summarizes the 2006 results of the North Dakota Land Valuation Model. The model is used annually to estimate average land values by county, based on the value of production from cropland and non-cropland. The county land values developed from this procedure form the basis for the 2006 valuation of agricultural land for real estate tax assessment. The average "all land value" from this analysis is multiplied by the total acres of agricultural land on the county abstract to determine each county's total agricultural land value for taxation purposes. The State Board of Equalization compares this value with the total value assessed to agricultural property in each county. Each county is required by state statute to assess a total value of agricultural property within 5 percent of this value. The average value per acre of all agricultural land in North Dakota increased by 6.68 percent based on the value of production. Cropland value increased by 6.4 percent and non-cropland value increased by 7.76 percent. The formula capitalization rate was below the minimum set by the State Legislature, therefore the minimum rate of 8.3 percent was used. Changes in market value are included for comparison. Market value data are from the annual County Rents and Values survey conducted by North Dakota Agricultural Statistics Service.Land valuation, real estate assessment, agricultural land, Land Economics/Use,