Species Interactions in Crop Communities PDF

1/15/2023 Species interactions in crop communities ▪ By paying attention to the ecology of crop community, it is possible to create beneficial...

1/15/2023 Species interactions in crop communities ▪ By paying attention to the ecology of crop community, it is possible to create beneficial interactions and emergent qualities that not only reduce the need for external inputs but also increase yield ▪ Species interaction in agroecosystem; i) Interference at the community level ii) Complexity of interactions iii) Mutualism iv) Intercropping 1 2 Interference at the community level ▪ Three types of interference i) removal interference ▪ Removal and addition interference ii) addition interference Can go on simultaneously leading to different iii) removal and addition interference type of interactions Example, pollination (removal of nectar and ▪ Removal interference addition to pollen) and biological nitrogen The environmental impact consists of the fixation (additon to fixed nitrogen by bacteria removal of some resource by one or both of the interacting organisms and removal of nitrogen by the legume) ▪ Addition interference One or both organisms adds some substance or structure to the environment 3 4 1  1/15/2023 5 6 ii) Complexity of interactions iii) Mutualism ▪ The way in which the various ▪ Likely to result of coexisting species populations of a crop continuing in the same evolutionary direction, coevolving adaptations for community influence the achieving mutual benefit through some community as a whole kind of close association through their interferences ▪ The types of mutualisms that are may be complex and difficult commonly recognized include; to discern a) Inhabitational mutualisms ▪ In agroecosystems, - One mutualist lives wholly or partly combining species with inside the other. A classic example is the relationship between Rhizobium slightly different bacteria and leguminous plants. physiological characteristics - The N fixing bacteria in this or resource needs is an relationship cannot function outside of important way of allowing for the nodules formed on the plant roots the coexistence of species in a multiple cropping community 7 8 2  1/15/2023 c) Indirect mutualisms - The interactions among a set of species modify the environment in which they all live to the benefit of the mixture - An example – polyculture agroecosystem b) Exhabitational mutualism - A tall crop species can modify - The organisms involved are relatively independent physically but interact conditions of the microclimate to the benefit of associated crop directly. species and the presence of several - An example is the relationship between a flowering plant and its pollinating crops attracts a range of beneficial insect. arthropods that facilitate the biological management of potential - Many crop plants are unable to produce fertile seed without pollination pests from bees, and the bees depend on the crop plants for the main source of - Involve more than two species food on the crop plants for their main source of food in the form of nectar and pollen 9 10 iv) Intercropping ▪ Whenever two or more crops are planted together in the same cropping system, the resulting interactions can have mutually beneficial effects and effectively reduce the need for external inputs ▪ Traditional example; corn-bean- squash polyculture ▪ Beans nodulate active biological fixation of N, fixed N is made directly available to the corn through mycorrhizal fungi connections between root systems and the squash helps control weeds 11 12 3