1. Cropping Production Systems AGRO 103 Crop Production

2. Chapter Objectives Introduce components of sustainable field crop production systems. Analyze and examine how these components interact with each other and how they are integrated into profitable and environmentally sustainable systems in commercial and smallholder farming operations in Zimbabwe. To encourage development of sustainable cropping calendars. Reference: The key reference to multiple cropping is the American Society of Agronomy. 1976. Multiple cropping special publication Number 27. Madison. Ruthenberg, H. 1976. farming systems in the tropics. 2 nd edition, Oxford university Press

3. Objectives Of Crop Production Systems Crop production systems must have objectives which should be met by the growing procedures adopted. “To produce the maximum yield of utilisable products as economically and efficiently as possible” For food crop that is directly consumed: “maximising yields is generally the objective” For crops that cannot be consumed directly and require some modification before they are suitable for consumption. Yield maximisation is not the only objective.

4. Objectives Of Crop Production Systems The suitability for processing becomes an important issue. For crops requiring processing, yield and quality are important. Producing crop products and animal food is an objective of some crop production systems. Yield is also not the only objective. Crops can be produced to supply raw materials to industry. Quality requirements of the industrial process must be met. Is the maximisation of yield necessarily a sensible objective in crop production systems?

5. Objectives Of Crop Production Systems Money is often the ultimate product required from the sale of crop products. Consider profit and return on investment. Crop production involves the use of a number of resources. consider efficiency of use of resources. Goals of smallholder cropping systems Achieving household food security Maximising monetary returns to farm resources ie maximise profits Increasing/maintaining adequate and stable household income for food and non- food needs etc through farm production. Having desirable leisure time for recreation and non- agricultural activities. Self development of the members of the household. Education Acquiring assets eg cattle Homestead improvement Increased investment on the farm.

6. Multiple cropping Definitions Multiple cropping is a centuries old practice which is normally done in areas where there is pressure on land due to increasing human populations. It maximises production per unit area over time through space (spatial) and time (temporal) maximisation. It is more prevalent in the tropics where temperature and rainfall favour all year round cropping. There are many forms of multiple cropping and it can be broken down as follows:

7. Multiple cropping cont.. Intercropping: is the practice of growing two or more crops in proximity. The most common goal of intercropping is to produce a greater yield on a given piece of land by making use of resources that would otherwise not be utilized by a single crop. It has many forms which include: Mixed intercropping: It is defined as a system of sowing two or three crops together on the same land, one being the main crop and the others the subsidiaries in no particular pattern. It intensifies cropping over time and space by growing two or more crops on the same field over time. Most popular practices are maize/cucurbits, maize/cowpea, maize groundnuts, maize/sunflower. In Zambia, cassava/maize/pumpkins/sweet potato. This intercropping system is difficult to improve scientifically.

8. Mutiple Cropping cont.. Row intercropping: Not well established in Zimbabwe. The commonest is maize/bean in East Africa, Maize/pigeon in Malawi, Maize/cowpea in West Africa. In Zimbabwe, maize/beans is most common. An example is two rows or three rows maize and two or three rows component crop. There is interaction between species in different rows. There is room for improvement of row intercropping e.g crop variety trials, spacing, density and spatial arrangement trials. Strip Intercropping: two or more crops grown in different strips, wide enough to allow independent cultivation but narrow enough for crops to interact agronomically. The management aims at utilising space while minimising interaction between species.

9. Multiple Cropping cont... Relay intercropping: A form of intercropping in which two or more crops grow simultaneously during part of the life cycle of each; that is, a second crop is planted before the first crop matures. Sequential Cropping This is growing of two or more crops in sequences on the same field per year. It has many forms which include: Double cropping: growing two crops a year one after the other. Popular in areas with bimodal rainfall patterns and those under irrigation but can also be done in areas with unimodal rainfall patterns. Summer maize and winter wheat in the Highveld or Summer Cotton and winter wheat in the Lowveld. Characteristics of double cropping include: All crops are main crops Management should facilitate timely planting for optimum productivity of the two crops Frequently varied for sustainable production where a legume or a fallow period is introduced to improve soil fertility and structure and also to break disease and pest cycles eg Cotton/wheat/soyabean/wheat/maize/wheat. Easy to research on one crop per time.

10. Multiple Cropping cont.. Triple cropping: Growing three crops on one field per year. Most common in humid tropics of Asia with three crops of rice on the same piece of land. In Zimbabwe more common in the horticultural industry of mixed agronomic crops and horticulture. Quadruple cropping: growing four crops on one piece of land per year. Most common in Asia. Ratoon cropping: When a crop is harvested and allowed to regrow from the crowns or root systems, the term ratoon cropping is used. Sugarcane, alfalfa, sorghum by the Tonga in the Zambezi valley, coffee, pigeon pea and sudan grass.

11. LAND EQUIVALENT RATIO (LER): the ratio of the area under sole cropping to the area under intercropping needed to give equal amounts of yield at the same management level. It is the sum of the fractions of the intercropped yields divided by the sole-crop yields. LER = (Yij/Yii )+ (Yji/Yjj) Where, Y= Yield per unit area Yii and Yjj = sole crop yields of the component crops i and j Yij and Yji = intercrop yields Partial LER values Li and Lj represents rates of the yields of crops i and j when grown as intercrops relative to sole crops. Li = (Yij/Yii ) Lj = (Yji/Yjj), LER=Li+Lj