Improving the Traditional Acacia Senegal-Crop System in Sudan: The Effect of Tree Density on Water Use, Gum Production and Crop Yields

Abstract

The traditional Acacia senegal bush-fallow in North Kordofan, Sudan, was disrupted and the traditional rotational fallow cultivation cycle has been shortened or completely abandoned, causing decline in soil fertility and crop and gum yields. An agroforestry system may give reasonable crop and gum yields, and be more appealing to farmers. We studied the effect of tree density (266 or 433 trees ha À1 ) on two traditional crops; sorghum (Sorghum bicolor) early maturing variety and karkadeh (Hibiscus sabdariffa), with regard to physiological interactions, yields and soil water depletion. There was little evidence of complementarity of resource sharing between trees and crops, since both trees and field crops competed for soil water from the same depth. Intercropping significantly affected the soil water status, photosynthesis and stomatal conductance in trees and crops. Gum production per unit area increased when sorghum was intercropped with trees in low or high density. However, karkadeh reduced the gum yield significantly at high tree density. Yields of sorghum and karkadeh planted within trees of high density diminished by 44 and 55% compared to sole crops, respectively. Intercropping increased the rain use efficiency significantly compared to trees and field crops grown solely. Karkadeh appears to be more appropriate for intercropping with A. senegal than sorghum and particularly recommendable in combination with low tree density. Modification of tree density can be used as a management tool to mitigate competitive interaction in the intercropping system. Introduction and background

Ethephon: a tool to boost gum arabic production from Acacia senegal and to enhance gummosis processes

“…This confirmed on a larger scale and with the conventional tapping system the preliminary results of Bhatt and Ram in India (1990). In the local provenance and despite the huge intratreatment variability, which is common to gum production trials in A. senegal (Dione and Vassal 1998;Gaafar et al 2006), the increase was significant, as the gum yield was increased by 600 % as compared to the untreated trees. The highest concentration of ethephon (120 mg/tree) gave lower gum yield than the lower (40 mg/tree).…”

“…The lack of responsiveness could also be related to the age of the trees (24 years at this location). In Sudan, A. senegal trees are usually cleared when they are 15-20 year old (Ballal et al 2005a) and the maximum gum yield is obtained from trees about 15 year of age (Gaafar 2005). Future studies on the use of ethephon in A. senegal should therefore focus on younger trees.…”

“…The uncertain gum yield in the sub-humid zone may be related to sporadic late rainfall inducing erratic re-foliation in this area. The question is still open, as few studies have assessed this issue (Dione and Vassal 1998;Ballal et al 2005b;Gaafar et al 2006), and the choice of the tapping time remains uneasy, particularly when A. senegal is introduced in new areas. A two-week delay can reduce the yield by 50 % in Northern Cameroon (Harmand et al 2012).…”

Growth and yield of maize and timber trees in smallholder agroforestry systems in Claveria, northern Mindanao, Philippines

“…Agroforestry systems with trees planted at wide spacing will result in higher crop yields, because of reduced tree-crop competition, reduced tree establishment and management costs and in larger tree diameter growth (Muchiri et al 2002;Gaafar et al 2006). In China, planting the fast-growing timber Paulownia elongata S. Y. Hu more densely than 5 9 20 m (100 trees ha -1 ) will reduce intercrop yields substantially.…”

Traditional agroforestry systems as tools for conservation of genetic resources of Milicia excelsa Welw. C.C. Berg in Benin

“…In the last three decades, agroforestry has been widely promoted in the tropics as a natural resource management strategy that attempts to balance the goals of agricultural development with the conservation of soils, water, local and regional climate, and, more recently, biodiversity . Various aspects of tropical agroforestry have also been recently reviewed, such as the history and dynamics of agroforestry systems (Kumar and Nair 2004;Miller and Nair 2006;Peyre et al 2006), socioeconomic aspects (Montambault and Alavalapati 2005), ecological interactions and management implications (Das and Chaturvedi 2005;Lengkeek et al 2005;Garcia-Barrios and Ong 2004;Gaafar et al 2006;Sharma and Ashwath 2006), and genetic resources and biodiversity conservation (Izac and Sanchez 2001;Schroth et al 2004;Teklehaimanot 2004;Atta-Krah et al 2004;Simons and Leakey 2004;McNeely 2004;Acharya 2006).…”