Yield stability of cassava, maize, soya bean and cowpea intercrops

Abstract

The yield stability of intercropping systems is important in developing cropping systems that produce economic yields over a wide range of environments. Field studies were conducted during the 1997/98 and 1998/99 growing seasons at three locations in the forest and forest–savannah transition zones of Ghana to determine yield, land use efficiency and yield stability of cassava (Manihot esculenta), maize (Zea mays), soya bean (Glycine max) and cowpea (Vigna unguiculata) intercrop systems. The cropping systems consisted of a factorial combination of two cassava varieties: ‘Gblemoduade’ (an improved, highly branched variety) and ‘Ankra’ (a local variety with fewer branches) and three spatial arrangements. Cowpea rows were planted in the minor season into cassava as a successive crop to maize and soya bean after their harvest in the major season. Intercropping significantly reduced grain or tuber yield of maize, cassava ‘Gblemoduade’ and cassava ‘Ankra’ by 23–70%, 16–49% and 24–64%, respectively. Maize yield decreased with increased number of soya bean rows. ‘Gblemoduade’ outyielded ‘Ankra’ by more than 100% under both intercrop and sole crop. The yield of soya bean increased with increased number of soya bean rows, but did not differ in response to the cassava variety. However, cowpea yield was higher when intercropped with ‘Ankra’ than with ‘Gblemoduade’. The intercrops had higher land use ratios (LER=1·27–2·83) and were more stable than the sole crops. Intercrops involving ‘Ankra’ had higher LER (2·14–2·18) than systems with ‘Gblemoduade’ (LER=1·83–1·99), but their yield stabilities were similar.

Biotic interactions, ecological knowledge and agriculture

“…Clearly, longerterm and multi-site investigations are needed to determine whether intercropping improves system stability and to identify long-term impacts on the agroecosystem. A few studies have attempted to address stability and risk ( Thiaw et al 1993) and (Dapaah et al 2003), and others have proposed methods and designs for assessing risk (Mead et al 1986;Trenbath 1999;Connolly et al 2001).…”

“…Nonetheless, more interdisciplinary, collaborative work will improve our ability to identify successful integrated weed, disease and arthropod pest management strategies ( Norris & Kogan 2005). Crop diversification through intercropping is mostly being researched in the tropics and subtropics and can be highly productive low input options for farmers in many countries (Thiaw et al 1993;Trenbath 1999;Dapaah et al 2003); although research is being done in developed countries (Baumann et al 2002a), there is little evidence of adoption by farmers (personal observation). In the past the same could be said of agroforestry, but interest in alley cropping and other types of agroforestry is increasing in the USA and Canada as an option for marginal land not only to sustain good crop productivity and provide organic matter inputs for organic production but also to increase carbon sequestration and improve the efficiency of nutrient cycling (Zinkhan & Mercer 1997;Jordan 2004;Thevathasan & Gordon 2004).…”

Intercropping

“…Intercropping of cereals and legumes is important for the development of sustainable food production systems, particularly in cropping systems with limited external inputs (Bulson et al 1997 ;Dapaah et al 2003 ) . In the tropics, cereal/legume intercropping is commonly practiced because of yield advantages, greater yield stability and lower risks of crop failure that are often associated with monoculture (Jensen 1996b ;Hauggaard-Nielsen et al 2001a ;Tsubo et al 2005 ) .…”

“…They are assumed to have potential advantages in productivity, stability of outputs, resilience to disruption and ecological sustainability, although they are sometimes considered harder to manage (Vandermeer 1989 ) . Yield increments resulting from mixed intercropping (Jensen 1996b ;Anil et al 1998 ;Dapaah et al 2003 ;Chen et al 2004 ) were attributed mainly to the presence of complimentary effects, better resource use ef fi ciency of the mixed cultures and the buffering effects of the mixtures against diseases and weeds (Willey 1979b ;Anil et al 1998 ) (Table 1 ).…”

Agricultural extension, technology adoption and household food security : evidence from DRC

“…Generally, intercropping is also associated with higher yield stability (Dapaah, Asafu-Agyei et al, 2003).…”