Fertiliser trees for sustainable food security in the maize-based production systems of East and Southern Africa. A review

Abstract

-The negative effects of soil fertility depletion on food security, especially among smallholder farmers in Africa, is of economic importance, and may be worsened by climate change and rising global fertiliser prices. Substantial efforts and investment have gone into development of alternative soil fertility management options. These include vigorous research and development of N-fixing plants or "fertiliser trees", that has been on-going in the last two decades in East and Southern Africa. In this paper, we review several studies conducted both on-station and on-farm and synthesise the results in terms of improvements in soil physical, chemical and biological properties, and crop yield in response to fertiliser trees. Our major findings are that (1) fertiliser trees add more than 60 kg N ha −1 per year through biological nitrogen fixation (BNF); (2) nutrient contributions from fertiliser tree biomass can reduce the requirement for mineral N fertiliser by 75%, translating to huge savings on mineral fertilisers; (3) fertiliser trees were also shown to substantially increase crop yield. A meta-analysis has further provided conclusive evidence that with good management, fertiliser trees can double maize yields compared with local farmer practices of maize cultivation without addition of external fertilisation. (4) Financial analyses showed that fertiliser tree systems are profitable and also have higher net returns than the farmers' de facto practice, i.e. continuous maize cropping without fertiliser. We conclude that widespread adoption and scaling up of fertiliser trees can reduce the amount of mineral fertiliser needed, maintain the soil ecosystem, and positively impact on the livelihoods of farm households in southern Africa.

Agricultural success from Africa: the case of fertilizer tree systems in southern Africa (Malawi, Tanzania, Mozambique, Zambia and Zimbabwe)

“…The others are Gliricidia sepium, Leucaena spp., Calliandra calothyrsus and Acacia spp. The work on a tree-crop intercrop system using G. sepium was developed by ICRAF in southern Malawi to address small landholding size (Akinnifesi et al, 2010). It is a modification to address key shortcomings that affected crop performance, including eliminating the 'hedge competition effect'.…”

“…To ensure substantial contribution in terms of amount of nitrogen fixed and biomass production, the choice of FTS promoted in a given area takes cognisance of agro-ecology and soil conditions. Technical details of FTS have been documented elsewhere Akinnifesi et al, 2010).…”

The role of knowledge, attitudes and perceptions in the uptake of agricultural and agroforestry innovations among smallholder farmers in sub-Saharan Africa

“…Agroforestry has been demonstrated to offer a wide range of benefits to farmers including the positive effect on their livelihoods through increasing crop yield and increased food security (Sileshi et al 2008a, Akinnifesi et al 2010, Garrity et al 2010) and income (Ajayi et al 2009), as well as improving farmers' ability to deal with the effects of climate change through improved rain use efficiency and yield stability under rain-fed agriculture (Verchot et al 2007. In addition, agroforestry is known for providing benefits to the environment by providing various ecosystem services (Sileshi et al 2007, Bhagwat et al 2008, Jose 2009, Nair et al 2009).…”

Impact of Soil Fertility Replenishment Agroforestry Technology Adoption on the Livelihoods and Food Security of Smallholder Farmers in Central and Southern Malawi

“…In Africa, and particularly southern Africa, the main constraint to agricultural productivity is soil nutrient deficiency (Scoones & Toulmin, 1999;Sanchez et al, 1997). For this reason, agroforestry research in the region has focused on soil fertility replenishment (SFR) technologies over the years and the adoption and scaling-up of these practices is the main thrust of the ongoing on farm research (Akinnifesi et al, 2008;Akinnifesi et al, 2010). SFR encompasses a range of agroforestry practices aimed at increasing crop productivity through growing trees (usually nitrogen-fixing), popularized as fertilizer tree systems, directly on agricultural land.…”

“…SFR encompasses a range of agroforestry practices aimed at increasing crop productivity through growing trees (usually nitrogen-fixing), popularized as fertilizer tree systems, directly on agricultural land. Fertiliser tree systems involve soil fertility replenishment through on-farm management of nitrogen-fixing trees (Akinnifesi et al 2010;Mafongoya et al, 2006). Fertiliser tree systems capitalise on biological N fixation by legumes to capture atmospheric N and make it available to crops.…”