Mineralization and N-use efficiency of tree legume prunings from fertilizer tree systems and low quality crop residues in Malawi

There is substantial evidence that fertilizer tree systems are capable of maintaining increased and sustainable crop production on low fertility soils in southern Africa, thus reducing the required amount of chemical fertilizer. However, crop yield increase in soils amended by fertilizer tree systems can only be optimized if nutrient release by the organic materials and nutrient demand by the crop are in synchrony. The decomposition and N release patterns of high quality tree prunings (gliricidia and sesbania) and crop residues (pigeon pea leaves and roots, and maize stover) were studied to understand the N use efficiency of fertilizer tree systems. The treatment were (1) quality pruning residues from gliricidia (Gs) and sesbania (Ss), (2) three medium quality residue levels including pigeon pea leaves (Pea-L), pigeon pea leaves + roots (Pea-LR) and pigeon pea roots (Pea-R), and (3) two rates of maize stover (Stover-1 and Stover-2) as low quality residues, and control (no crop residues, no tree prunings). The treatment combinations were laid out as a randomized complete blocks design. Mixtures of tree prunings with 2.5 t ha-1 maize stover increased maize N uptake and grain yield whereas 5 t ha-1 maize stover reduced maize N uptake and grain yield during the wetter season. Mixtures of Pea-R, Stover-1 or Stover-2 with tree prunings depressed yields during the drier season. Stover-2 had the highest N fraction immobilized N, respectively 15 and 35% N during the wetter and drier conditions. Weconclude that (1) mixing of high quality tree prunings with crop residues may enhance the decomposition of low quality crop residues but there is no special interaction, and (2) remineralization of N immobilized early in the season by the low quality organic materials is stimulated by welldistributed rainfall

Rootstock growth and development for increased graft success of mango (Mangifera indica) in the nursery

The graft success of seedlings depends on rootstock size and the skills of grafters. A study was carried out to evaluate the effects of rootstock diameter (at root collar), skills and experience of grafters on mango seedling thinning and grafting. Skilled and unskilled grafters were involved in grafting mango plants for at least three consecutive months. Different rootstock sizes based on root collar diameter of mango seedlings were assessed. The results showed significant differences in graft-take among three groups of nurserymen. The skills and experience of grafters had a significant effect on graft success. The late emerging seedlings showed higher increase in height and diameter after thinning. A higher survival (> 75%) and reduced time to graft-take (19 days) were achieved with thicker rootstocks (0.7 cm) than thinner rootstocks (0.3 cm). The early emerging plants produced more leaves than late emerging plants after grafted. It was concluded that a higher graft-take can best be achieved with skilled grafters and thicker rootstocks

Ripening stage and drying method affecting colour and quality attributes of Ziziphus mauritiana fruits in Zimbabwe

Ziziphus mauritiana Lamk. (Ber) fruit is harvested at different stages of ripening in the Zambezi valley of Zimbabwe. We hypothesize that the organoleptic quality attributes of fruits depend on post-harvestdrying method and ripening stage at harvest. This study was carried out to evaluate the effect of different stages of ripening on the quality of Z. mauritiana fruits during drying. The fruits were graded into green, yellowish-brown and brown categories and these formed the treatments. Some of these fruits were blanched before drying for 1, 2 and 3 weeks under the solar dryer and the open sun drying methods. The green fruits lost significantly (

Effective preconditioning methods for in vitro propagation of Uapaca kirkiana Müell Arg. tree species

The objective of the study was to determine efficient preconditioning methods for in vitro multiplication of Uapaca kirkiana plant materials from mature stock plants. The efficacy of sodium hypochlorite(NaOCl), calcium hypochlorite {Ca(OCl2)2} or mercuric chloride (HgCl2) as surface sterilant was evaluated in decontaminating explants excised from grafted and field-collected U. kirkiana trees.Different Murashige and Skoog (MS) medium supplements were evaluated for shoot multiplication and root regeneration. Results indicated that preconditioning grafted U. kirkiana trees before excisingexplants and decontaminating explants in 0.1% w/v HgCl2 were effective methods in establishing aseptic cultures (80%). Lateral shoots (new shoots) responded positively to shoot multiplication on ¾strength MS medium supplemented with a combination of 0.1 mg/L benzylaminopurine, 0.04 mg/L naphthaleneacetic acid and 0.3 mg/L casein hydrolysate. High concentrations of thidiazuron (>0.1 mg/L)suppressed bud break. Rooting (36%) was achieved with ½ MS medium supplemented with 2.5 mg/L indole-3-butyric acid. Plantlets were successfully hardened off. In vitro multiplication of mature U.kirkiana plant materials was achieved using lateral shoots excised from grafted U. kirkiana trees after preconditioning with fungicides

Genetic diversity within and among Southern African provenances of Uapaca kirkiana müell. Årg using morphological and AFLP markers

Domestication of Uapaca kirkiana Müell. Arg is a high priority for improving rural livelihoods of smallholder farmers in southern and eastern Africa. Domestication efforts require knowledge of ecological adaptive traits and intra-specific variation. Morphological traits and amplified fragment length polymorphic (AFLP) markers were used to assess genetic variation in twelve provenances of U. kirkiana collected from five countries in southern and eastern Africa. Assessment of tree morphological traits showedsignificant differences (p< 0.05) between provenances where Zimbabwean and Zambian provenances grew much faster than those from Tanzania and Malawi (except Phalombe). Mean Nei’s (H) genetic diversity of AFLP showed high diversity within the provenances H= 0.181 to 0.321 with mean of 0.256. An analysis of molecular variance (AMOVA) showed that most genetic variation (90.8 %) resided within provenances, while only 8.2 % was variation among provenances. There was no geographical pattern of variation in growth and morphological traits among the seed sources. Chipata provenance from Zambia was the most diverse while Mapanzure from Zimbabwe was the least diverse but more superior in height growth and earliest in fruiting. The pattern of genetic diversity in U. kirkiana indicates existence of genetic drift and high gene flow between provenances suggesting that regional collections and conservationstrategies should consider differences by focussing on the main range of the species.Keywords: AFLP - Conservation-Domestication- Genetic diversity- Provenance- Uapaca kirkiana- UPGM

A decision support tool for propagating Miombo indigenous fruit trees of southern Africa

Indigenous fruit trees (IFTs) contribute to the livelihoods of rural households as sources of food, income and medicine. Conservation and domestication of IFTs involve germplasm selection, collection,multiplication and evaluation. In addition, biodiversity and genetic improvements have been realized through propagation. However, there are numerous challenges when propagating indigenous trees andthe choice of appropriate propagation techniques determines the success of domestication programme. In this paper we synthesize different propagation methods used for indigenous fruit trees,and propose a decision support tool based on desirable attributes of individual IFT, technical requirements, expertise of the propagators and relative cost of implementing the technology in addition to field performance and tree management. Depending on circumstances, this decision support tool can be used to quickly choose a propagation method for a given fruit tree so as to maximize on germplasm collection, multiplication and evaluation without compromising field performance and management of the fruit trees

Water application rate and frequency affect seedling survival and growth of Vangueria infausta and Persea americana

Adequate amount of water is critical to successful tree nursery operation among resource-constrained smallholder farmers in Africa. Two  experiments were undertaken with the objectives of evaluating effects of water application rate and frequency on seedling growth and survival of Persea americana and Vangueria infausta. In experiment 1, water was applied to seedlings at 500 ml per 1 L polyethylene bag daily and at two, four and six day intervals. In experiment 2, water was applied to seedlings every two days at the rate of 25, 50, 100 and 150 ml per polyethylene bag. The results indicated that V. infausta was more responsive to the rate than frequency of water application. Water application of 100 ml every two days was effective in promoting seedlings growth and survival for both species. Application of 500 ml of water every two days promoted growth of P. americana, while watering frequency had no significant effect on V. infausta. It is concluded that V. infausta seedlings require less frequent watering. Both species could be successfully raised with 100 ml of water applied every two days.Key words: Nursery irrigation, nutrient reserves, root collar diameter, seedling mortality

What Is the Evidence Base for Climate-Smart Agriculture in East and Southern Africa? A Systematic Map

More than 500 million USD will soon be invested in climate-smart agriculture (CSA) programmes in sub-Saharan Africa. Improving smallholder farm management is the core of most of these programmes. However, there has been no comprehensive information available to evaluate how changing agricultural practices increases food production, improves resilience of farming systems and livelihoods, and mitigates climate change—the goals of CSA. Here, we present a systematic map—an overview of the availability of scientific evidence—for CSA in five African countries: Tanzania, Malawi, Mozambique, Zimbabwe and Zambia. We conducted a systematic literature search of the effects of 102 technologies, including farm management practices (e.g., leguminous intercropped agroforestry, increased protein content of livestock diets, etc.), on 57 indicators consistent with CSA goals (e.g., yield, water use efficiency, carbon sequestration, etc.) as part of an effort called the "CSA Compendium". Our search of peer-reviewed articles in Web of Science and Scopus produced 150,567 candidate papers across developing countries in the global tropics. We screened titles, abstracts and full texts against predetermined inclusion criteria, for example that the investigation took place in a tropical developing country and contains primary data on how both a CSA practice and non-CSA control affect a preselected indicator. More than 1500 papers met these criteria from Africa, of which, 153 contained data collected in one of the five countries. Mapping the studies shows geographic and topical clustering in a few locations, around relatively few measures of CSA and for a limited number of commodities, indicating potential for skewed results and highlighting gaps in the evidence. This study sets the baseline for the availability of evidence to support CSA programming in the five countries

Explore before you restore: Incorporating complex systems thinking in ecosystem restoration

Abstract The global movement for ecosystem restoration has gained momentum in response to the Bonn Challenge (2010) and the UN Decade on Ecosystem Restoration (UNDER, 2021–2030). While several science‐based guidelines exist to aid in achieving successful restoration outcomes, significant variation remains in the outcomes of restoration projects. Some of this disparity can be attributed to unexpected responses of ecosystem components to planned interventions. Given the complex nature of ecosystems, we propose that concepts from Complex Systems Science (CSS) that are linked to non‐linearity, such as regime shifts, ecological resilience and ecological feedbacks, should be employed to help explain this variation in restoration outcomes from an ecological perspective. Our framework, Explore Before You Restore, illustrates how these concepts impact restoration outcomes by influencing degradation and recovery trajectories. Additionally, we propose incorporating CSS concepts into the typical restoration project cycle through a CSS assessment phase and suggest that the need for such assessment is explicitly included in the guidelines to improve restoration outcomes. To facilitate this inclusion and make it workable by practitioners, we describe indicators and methods available for restoration teams to answer key questions that should make up such CSS assessment. In doing so, we identify key outstanding science and policy tasks that are needed to further operationalize CSS assessment in restoration. Synthesis and applications. By illustrating how key Complex Systems Science (CSS) concepts linked to non‐linear threshold behaviour can impact restoration outcomes through influencing recovery trajectories, our framework Explore Before You Restore demonstrates the need to incorporate Complex Systems thinking in ecosystem restoration. We argue that inclusion of CSS assessment into restoration project cycles, and more broadly, into international restoration guidelines, may significantly improve restoration outcomes. </jats:p