Residual effects of fallows on selected soil hydraulic properties in a kaolinitic soil subjected to conventional tillage (CT) and no tillage (NT)

Improved fallows have been used to reduce time required for soil fertility regeneration after cropping in low input agricultural systems. In semi-arid areas of Southern Africa, Acacia angustissima and Sesbania sesban are among some of the more widely used improved fallow species. However the residual effects of improved fallows on soil hydraulic properties during the cropping phase is not known. The aim of this study was to quantify the residual effects of fallows and tillage imposed at fallow termination on soil hydraulic properties (infiltration rates, hydraulic conductivity and soil porosity) during the cropping phase. Treatments evaluated were planted fallows of Acacia angustissima, Sesbania sesban and natural fallow (NF) and continuous maize as a control. Steady state infiltration rates were measured using a double ring infiltrometer and porosity was calculated as the difference between saturated infiltration rates and tension infiltration measurements on an initially saturated soil. Unsaturated hydraulic conductivity (K-o) and mean pore sizes of water conducting pores were measured using tension infiltrometer at tensions of 5 and 10 cm of water on an initially dry soil. While there was no significant difference in steady state infiltration rates from double ring infiltrometer measurements among the fallow treatments, these were significantly higher than the control. The steady state infiltration rates were 36, 67, 59 and 68 mm h(-1) for continuous maize, A. angustissima, S. sesban and NF respectively. Tillage had no significant effect on steady state infiltration rate. Pore density at 5 cm tension was significantly higher in the three fallows than in maize and varied from 285-443 m(-2) in fallows, while in continuous maize the pore density was less than 256 m(-2). At 10 cm tension pore density remained significantly higher in fallows and ranged from 4,521-8,911 m(-2) compared to 2,689-3,938 m(-2) in continuous maize. Unsaturated hydraulic conductivities at 5 cm tension were significantly higher in fallows than in continuous maize and were 0.9, 0.7, 0.8 cm and 0.5 cm h(-1) for A. angustissima, S. sesban, NF and continuous maize, respectively. However there were no significant treatment differences at 10 cm tension. Fallows improved infiltration rates, hydraulic conductivity and soil porosity relative to continuous maize cropping. Through fallowing farmers can improve the soils hydraulic properties and porosity, this is important as it affects soil water recharge, and availability for plant growt

Soil organic carbon dynamics of improved fallow-maize rotation systems under conventional and no-tillage in Central Zimbabwe

Fallowing increases soil organic carbon (SOC) during the fallowing phase. However, this benefit is lost quickly during the cropping phase. The objective of this study was to evaluate SOC dynamics of an improved fallow-maize rotation under no-tillage (NT) and conventional tillage (CT) from time of fallow termination, through the next two cropping seasons. The treatments studied were improved fallows of Acacia angustissima (A. angustissima) and Sesbania sesban (S. sesban), natural fallow and continuous maize. Our hypothesis is that fallowing maintained higher SOC and lower soil bulk densities through the cropping phase when compared with continuous maize system and that NT maintained higher SOC when compared with CT. Soil organic carbon was significantly greater under fallows than under continuous maize from fallow termination to the end of the second cropping season. Soil organic carbon for the 0¿5 cm depths was 11.0, 10.0, 9.4 and 6.6 g kg¿1 for A. angustissima, S. sesban, natural fallow and continuous maize, respectively at fallow termination. After two cropping seasons SOC for the same depth was 8.0, 7.0, 6.1, 5.9 g kg¿1 under CT and 9.1, 9.0, 8.0, 6.0 g kg¿1 under NT for A. angustissima, S. sesban, natural fallow and continuous maize, respectively. Total SOC stocks were also higher under fallows when compared with continuous maize at fallow termination and after two cropping seasons. Soil bulk densities were lower under fallows when compared with continuous maize during the period of study. We concluded that fallows maintained greater SOC and NT sequestered more SOC than CT. Acacia angustissima was the better tree legume fallow for SOC sequestration when compared with S. sesban or natural fallow because it maintained higher SOC and lower bulk densities after two seasons of maize cropping

CLIMATE CHANGE AND VARIABILITY: SMALLHOLDER FARMING COMMUNITIES IN ZIMBABWE PORTRAY A VARIED UNDERSTANDING

Increasing awareness of risks associated with climate change and variability among smallholder farmers is critical in building their capacity to develop the necessary adaptive measures. Using farmer participatory research approaches and formal questionnaire surveys, interaction has been made with >800 farmers in two distinct smallholder farming systems of Makoni and Wedza Districts in eastern Zimbabwe to determine the current level of understanding of climate change and variability, current responses to perceived changes, as well as identify sources of agro-meteorological information. The results indicated that farmers portrayed a varied understanding both within and across the study sites. While poor rainfall distribution was seen as the major indicator for climate change by over two-thirds of the respondents in both sites, more farmers in Makoni attributed delay in onset of rains, high incidences of flush floods and unpredictable \u2018wind movements\u2019 yielding cyclones to climate change. In Wedza, it was recurrent droughts, winter and summer temperature extremes, and increased pest and disease incidences for both crops and livestock that indicated climate change. Perceived changes were linked more to natural and human forces (Makoni), unknown forces as well as breakdown in cultural norms and beliefs and rise of Christianity (Wedza). Disparities between the two sites could be attributed to the inherent differences of the communities in terms to their social settings. The national extension, Agritex, was ranked first by 50-60% of the farmers as major source of weather information. Electronic media (radio and television) ranked second with 47% of farmers in Makoni and 35% in Wedza. Concerns were raised over inadequacies of such information, apparent lack of reliability, timing and frequency of dissemination that directly influenced the utilisation of the information. Common coping strategies included early planting which was the more prevalent in Makoni, while combinations of cereals and legumes were a preferred solution in Wedza. We concluded that farmers\u2019 interaction with various information sources and knowledge sharing platforms needs to be enhanced in order to deepen their understanding as well as increase their capacity to respond to pressures of climate variability and change.L\u2019am\ue9lioration des connaissances des petits fermiers sur les risques lies au changement du climat et sa variabilit\ue9 est un fait important pour l\u2019\ue9dification de leur capacit\ue9 de d\ue9velopper des mesures n\ue9cessaires d\u2019adaptation. En utilisant des m\ue9thodes de recherche participative et un questionnaire d\u2019enqu\ueate formelle, l\u2019interaction a \ue9t\ue9 faite avec plus de 800 fermiers de deux syst\ue8mes d\u2019exploitation distincts de districts de Makoni et Wedza \ue0 l\u2019Est du Zimbabwe, afin de d\ue9terminer le niveau actuel de compr\ue9hension du changement du climat et sa variabilit\ue9, les m\ue9canismes d\u2019adaptation aux changements per\ue7us, ainsi qu\u2019identifier les sources d\u2019information agro m\ue9t\ue9orologique. Les r\ue9sultats ont indiqu\ue9 que les fermiers avaient un niveau vari\ue9 de compr\ue9hension dans les deux sites d\u2019\ue9tude.Alors qu\u2019une faible distribution des pr\ue9cipitations \ue9tait consid\ue9r\ue9e comme \ue9tant l\u2019indicateur majeur du changement du climat par plus de 2/3 des r\ue9pondants dans les deux sites, la plupart des fermiers de Makoni ont affirm\ue9 que le retard dans l\u2019apparition des pluies, incidence \ue9lev\ue9e des inondations et mouvement du vent impr\ue9dictible r\ue9sultant du cyclone par le changement du climat. En Wedza, le changement du climat \ue9tait manifest\ue9 \ue0 travers les s\ue9cheresses r\ue9currentes, des temp\ue9ratures extr\ueames pendant l\u2019hiver et l\u2019\ue9t\ue9 ainsi que l\u2019accroissement d\u2019incidences de pestes et maladies affectant des cultures et le b\ue9tail. Les changements per\ue7us \ue9taient plus li\ue9s aux forces naturelles et humaines (Makoni), des forces inconnues aussi bien que la non-observance des normes culturales et les croyances et le d\ue9veloppement de la chr\ue9tient\ue9 (Wedza). Les disparit\ue9s entre les deux sites pourraient \ueatre attribu\ue9es aux diff\ue9rences inh\ue9rentes des deux communaut\ue9s en termes de leurs environnements sociaux. La vulgarisation nationale, Agritex, \ue9tait rang\ue9e la premi\ue8re par 50-60% des fermiers comme source majeur de l\u2019information sur le climat suivi du media \ue9lectronique (radio et t\ue9l\ue9vision) avec 47% des fermiers dans Makoni et 35% dans Wedza. Les probl\ue8mes \ue9voqu\ue9s \ue9taient li\ue9s au manque de consistance de l\u2019information, manque apparent de fiabilit\ue9, le temps et la fr\ue9quence de diss\ue9mination qui directement influencent l\u2019utilisation de l\u2019information. Les strat\ue9gies communes d\u2019adaptation consistaient en la plantation \ue0 temps sp\ue9cialement dans Makoni, pendant que les combinaisons des c\ue9r\ue9ales et des l\ue9gumes \ue9taient une solution pr\ue9f\ue9r\ue9e en Wedza. En conclusion, l\u2019interaction des fermiers avec des sources vari\ue9es d\u2019information et les plateformes de partage de connaissance ont besoin d\u2019\ueatre d\ue9velopp\ue9e afin d\u2019am\ue9liorer leur niveau de compr\ue9hension aussi bien renforcer leur capacit\ue9 \ue0 r\ue9pondre aux pressions du changement du climat et sa variabilit\ue9

Infiltration and runoff losses under fallowing and conservation agriculture practices on contrasting soils, Zimbabwe

Fallowing and conservation agriculture are sustainable farming practices that can be used for soil and water conservation. The objectives of the study were to evaluate the effects of different conservation agriculture practices on rainfall infiltration and soil and water losses across 4 sites, using simulated rainfall. The study was carried out at Domboshawa and the Institute of Agricultural Engineering and Chikwaka smallholder farming areas, 4 sites with different soil types. Conservation agriculture practices evaluated were mulch reaping (MR) and clean reaping (CR) at Domboshawa with 5% clay and the Institute of Agricultural Engineering (IAE) with 50% clay. The study also evaluated runoff losses from fallow plots subjected to no tillage (NT) and conventional tillage (CT) at ICRAF Domboshawa site (20% clay) and fallows subjected to CT in Chikwaka smallholder farming areas (4% clay). Infiltration rates were greater under conservation agriculture practices (>35 mm∙h -1 ) when compared to CT (<27-29 mm∙h -1 ). On fallows infiltration rates ranged from 24-35 mm∙h -1 when compared to <15 mm∙h -1 in maize under CT. Runoff losses were highest under CT at both Domboshawa and IAE sites, and were 21.5 and 15% respectively, while there was no runoff under MR and CR. At the ICRAF Domboshawa site, runoff ranged between 0-31% in fallows and was 57% in maize under CT. At Chikwaka runoff in CT maize was 58%, while in fallow plots runoff ranged 37-44%. Soil losses ranged from 0.2-0.3 t∙ha -1 per rainfall event in maize, while in fallows, soil loss ranged from 0-0.1 t∙ha -1 . The results showed that CT resulted in reduced infiltration rates, increased soil and water loss when compared to fallowing and conservation agriculture across different range of soils. Conservation agriculture practices and fallowing are potential sustainable cropping practices that reduce soil and water loss and increase water use efficienc

Perennial grains for Africa: possibility or pipedream?

Perennial grain crops have been proposed as a transformative approach to agriculture. Replacing annual staple crops with perennialized growth types of the same crops could provide environmental services, improve labour efficiency and weather resilience, reduce seed costs and produce livestock fodder or fuelwood production. Yet, the technologies and science for agricultural development in Africa have focused almost exclusively on annuals. In this paper, we review the literature to explore what has been potentially overlooked, including missed opportunities as well as the disadvantages associated with perennial grains. The case studies of pigeon pea and sorghum are considered, as an analogue for perennial grain crops in Africa. We find that a substantial number of farmers persist in ‘perennializing’ pigeon pea systems through ratoon management, and that sorghum ratoons are widely practiced in some regions. In contrast, many crop scientists are not interested in perennial traits or ratoon management, citing the potential of perennials to harbour disease, and modest yield potential. Indeed, an overriding prioritization of high grain yield response to fertilizer, and not including accessory products such as fodder or soil fertility, has led to multipurpose, perennial life forms being overlooked. Agronomists are encouraged to consider a wide range of indicators of performance for a sustainable approach to agriculture, one that includes management for diversity in crop growth habits

Taking technologies to a greater scale

Open Access ChapterThis chapter presents a definition of 'scaling' and outlines the key elements for success based on the experiences gained from Africa RISING research and dissemination in East and Southern Africa (ESA). Three examples are presented: (a) research and development partnerships; (b) community based scaling through seed systems; and (c) outdoor advertising for orange-fleshed sweet potato. It presents experiences and lessons learned from using these approaches to transfer and scale the technologies