Annual Arable Crops Research Articles

Biomass energy in Western Europe to 2050

Presently biomass energy supplies at least 2 EJ/yr (47 Mtoe) in OECD Europe, which is about 4% of total primary energy consumption (54.1 EJ). Estimates of the potential for bioenergy in the next century range from 2 to 20 EJ/yr. This paper estimates a potential of 9.0–13.5 EJ in 2050, which represents 17–30% of projected total energy requirements. This depends on assumptions of available land areas, achievable yields and the amount of recoverable residues utilized. Greater environmental and net energy benefits can be derived from perennial and woody energy crops compared to annual arable crops as alternative feedstocks for fossil fuels. The relative contribution of biofuels in the future will ultimately depend on markets and incentives, on R&D progress and on environmental requirements.

Bioethanol from grapes in the European community

The feasibility of fermenting grapes to produce bioethanol fuel in the European Community (E.C.) was assessed. The net energy balances, costs and environmental impacts were considered for a range of management scenarios. Typical wine producing vineyards cannot produce ethanol with a positive net energy balance, and costs are 4–6 times as great as those using wheat or sugar beet as raw materials. Wine production in the European Community exceeds demand by 20–40%. Producing ethanol for fuel from surplus wine in the European Community is a drain on energy and financial resources. It is possible to improve the performance of grapes as an energy crop, principally by raising yields. It was estimated that a net energy output of 69 GJ/ha is possible (with an energy output: input ratio of 1.8), and production costs (after deduction of revenue for co-products) could be reduced to 66 ECU/hl a ($0.80/1). Using these criteria it was calculated that annual crops such as wheat and sugar beet remain preferable to grapes as raw materials. However, the surplus land under grape vines is often steeply sloping and has thin, dry soils, which would be subject to considerable soil erosion if planted with arable crops; it is considered that perennial energy crops are more environmentally acceptable than annual arable crops.

Seasonality in tropical AIDS: a geographical analysis.

This paper presents evidence that the growth rate of the AIDS epidemic at the district level in Uganda, Central Africa, displays a seasonally recurring geographical pattern, with epidemic acceleration in some areas of the country in the first 8 months of each year. The spatial and temporal variations in acceleration appear to be correlated with the predominant agricultural systems in different parts of Uganda. Based upon the frequently hypothesized relationship between malnourishment and the progression to clinical AIDS in HIV-infected people, it is suggested that the variations in epidemic speed reflect the seasonal patterns of nutritional deficiency which occur under some tropical agricultural systems. These preliminary findings require further verification since they have important implications for directing nutrition-related remedial responses to the AIDS epidemic in tropical countries where malnutrition and endemic HIV infection coincide.

Crop water requirements of cotton

1. Attention is drawn to the enormous variations in yield experienced in commercial cotton growing under rain-fed conditions. Yields at Namulonge have ranged from 161 to 1163 lb./acre.2. In seeking an explanation of this enormous variation past and present fertilizer trials in Uganda have failed to show that much of this variation is due to nutrient status.3. From Manning's previous analysis of yields in relation to seasonal rainfall, over many district trials, it is evident that 20–25 in. of rainfall per season is optimum.4. The purpose of more recent studies has been to examine the effect of distribution of rainfall within the season. Clearly the pattern of crop water requirement, also within the season, must supersede a simple seasonal concept of crop water use.5. Experimental evidence, based on several seasons' data, led to the conclusion that evapotranspiration rates exceeding the commonly accepted figure of 0·8E must in fact occur in order to provide a satisfactory explanation of results recorded.6. The within-season pattern of water requirement of an annual arable crop is shown to be more dependent on its state of development than on the pattern of a physical model based on calculations of energy availability.