Effects of atmospheric ammonia (NH3) on terrestrial vegetation: a review.

Publisher Summary This chapter describes the various aspects of cereal-legume intercropping systems Intercropping is the growing of two or more crop species simultaneously in the same field during a growing season The intercropping of legumes with cereals offers scope for developing energy-efficient and sustainable agriculture The main types of intercropping include mixed intercropping, row intercropping, and strip intercropping Crop combinations differ with geographical location and there may be intercropping of tree crops, intercropping of tree and field crops, or intercropping of field crops Combinations of crops are determined primarily by the length of the growing season and the adaptation of crops to particular environments Different indices have been suggested for evaluating productivity and efficiency per unit area of land of cereal-legume intercrop systems These include comparisons of absolute yields, protein yields, caloric equivalent, and in economic terms, gross returns from intercrops and sole crops Differences in competitive ability affect the relative performance of component crops and thus the land equivalent ratio values of different cereal-legume intercrop systems It is found that phosphorus is a major nutrient that determines the production potential of most grain legumes usually intercropped with cereals

Cereal–Legume Intercropping Systems

Understanding maize–weed competition: resource competition, light quality and the whole plant

Publisher Summary A grass-legume association has been used in many countries of the world because a greater total herbage yield may be obtained by growing a grass and a legume in association, rather than in individual swards, where no fertilizer N is applied. Interferences and competition between legumes and associated grasses are of great importance in world pasture production. Such interspecific interferences are likely to be a dominating factor in the nonequilibrium, man-made and -managed pasture vegetation. It is generally accepted that grasses normally have a competitive advantage over legumes, and they tend to dominate pastures but to maintain high pasture productivity, a balance between grasses and legumes is desirable. This chapter examines the competitive relationships between grasses and legumes and also considers the way in which pasture management techniques alter the balance of legumes and grasses by manipulating the environment, which results in a competitive advantage to the legume component.

Competitive Aspects of the Grass-Legume Association

9 – Many Little Hammers: Ecological Management of Crop-Weed Interactions

RECENTLY the idea has been advanced that clean cultivation of field corn is not necessary and perhaps not even desirable (2, 3, 6 j . Proponents of growing corn without cultivating, point out that the accompanying weed growth controls soil erosion and adds additional organic matter to the soil. By using a specially designed mulch planter, the usual operations in seedbed preparation of plowing, discing, and harrowing are eliminated. Although heavier rates of fertilization are required to supply the nutritional requirements of both th,corn and the weeds, the additional cost of the fertilizer is more than offset by savings made in eliminating certain tillage operations. Thus far, few investigations have been carried out to measure the added requirements of weeds for essential nutrients as well as for moisture, when growing in association with corn plants. Previous investigations by the authors ( 5 ) concerning the extent to which common weeds compete with cultural plants for essential plant nutrients, raised serious doubts in their minds about the possibility, to say nothing of the practicability, of meeting the nutritive requirements of cultural plants growing in association with weeds simply by the addition of more fertilizer. The objective of these experiments was to gather som quantitative data relative to this point, particularly with regard to varying rates of phosphate fertilization.

William G. Colby

Papers

Plant Nutrient Competition Between Weeds and Corn1

Cation-Exchange Capacity of Plant Roots