Crop and weed responses to residue retention and method of weeding in first two years of a hoe-based minimum tillage system in semi-arid Zimbabwe

Many argue that residue retention and effective weed management are the two components limiting the uptake of conservation farming by smallholder farmers in southern Africa. An experiment was carried out at Matopos Research Station, Bulawayo, Zimbabwe to determine the effects of crop residue retention and eeding method on weed biomass, and maize (Zea mays)and sorghum (Sorghum bicolor) yields. The experiment was conducted in the 2004/05 and 2005/06 cropping seasons on clay loam and sandy soils. The study was set up as a split-plot design with residue retention (0, 25, 50,75 and 100% of previous season’s stover) as main-plot factor and weeding method (hoe-weeding and glyphosate applied with the Zamwipe®) as a sub-plot factor. Each treatment was replicated three times on each soil type. Hoe-made planting basins for maize (cultivar SC 403)and planting furrows for sorghum (variety Macia) were prepared after which residue was applied in the dry season. The crops were planted after the first effective rains of the season. Weed biomass and crop yield were measured under each treatment. In both seasons crop residue retention did not have a significant effect on crop yield irrespective of soil type. In both maize and sorghum in 2005/06 season, retaining the available crop residue(2.5 t ha-1 and below) did not result in significant weed suppression. The Zamwipe® proved difficult to use in both years resulting in significantly lower crop yield in the second season due to poorer weed control than observed in hoe-weeding. Furthermore, results from sorghum grown on the sandy soil suggest that the crop residue that was spread uniformly over the plots may have interfered with the Zamwipe®. Thus, the weed wipe requires further mechanical improvements. Since the effects of residue retention are viewed as cumulative, more detailed long-term studies are needed to understand the implications of residue retention in mixed croplivestock systems

Rolling out Zimbabwean approach to demand-led sanitation in most vulnerable communities

Rural WASH Project (2012-2016) is being implemented in 33 of 60 rural districts in five provinces of Zimbabwe aiming at improving WASH services. One of the major components under this project is the implementation of demand led sanitation and hygiene promotion which focuses on elimination of open defaecation through promotion of household sanitation technologies confirming to national standards. The approach is a hybrid of traditional CLTS, and PHHE and Zimbabwe technology specific sanitation approach. The results from the implementation for the last 23 months suggest a major breakthrough including construction of 57,542 household latrine and 525 ODF communities. It also demonstrated a strong potential of achieving sanitation SDG before 2030 if replicated nationwide with maintaining the current level of efforts. This paper describes the evolution of sanitation approaches in Zimbabwe and share unique experiences from the implementation of the demand led sanitation

Crop yield and weed growth under conservation agriculture in semi-arid Zimbabwe

Constraints to effective weed management may be the main reason for the small area under minimum tillage (MT) in smallholder farming in southern Africa. The effect of maize residue mulching and intensity of hand hoe weeding on the growth of weeds, cowpea (Vigna unguiculata cv. IT 86D-719) and sorghum (Sorghum bicolor cv. Macia) was investigated in the fifth and sixth years of a conservation agriculture (CA) field experiment at Matopos Research Station (28°30.92′E, 20°23.32′S). The experiment was a split-plot randomized complete block design with three replications. Tillage was the main plot factor (conventional tillage – mouldboard plough compared against MT systems – ripper tine and planting basins) and maize residue mulch rate (0, 4 and 8 t ha−1) the sub-plot factor. Hoe weeding was done either four times (high weeding intensity) or twice (low weeding intensity) during the cropping season. Planting and weeding were done at the same time in all treatments. There was markedly greater early season weed growth in MT systems relative to mouldboard plough (MBP) in both crop species. In sorghum, MT (planting basins: 40.3 kg ha−1; ripper tine: 34.8 kg ha−1) systems had higher cumulative weed biomass measured after planting than MBP (29.9 kg ha−1) system. Maize mulching was generally associated with increased mid- to late-season weed growth in the two crops probably due to improved soil moisture conservation during periods of low precipitation. Weed suppression by the maize mulch was observed only in sorghum and limited to early in the cropping season with no effect observed for the remainder of the sorghum rotation phase. The high weeding intensity treatment had lower weed growth in both crops and better sorghum yield than low weeding intensity. The MT systems had poor crop establishment which translated into low yields. Cowpea grain yield obtained from MT systems was less than 300 kg ha−1 compared to 413 kg ha−1 in MBP. The poor sorghum establishment in MT systems translated into low grain yield as sorghum grain yield was lowest in planting basins (2602 kg ha−1) and highest in MBP with 4159 kg ha−1. Results suggest that CA systems require early and frequent hoe weeding even after four years to reduce weed infestations and improve crop growth. This higher demand on a smallholder household's limited labor supply throughout the cropping season will be a key determinant of the spread and adoption of CA in southern Africa

Improving maize (Zea mays L.) performance in semi-arid Zimbabwe through micro-dosing with ammonium nitrate tablets

Although the application of small quantities of nitrogen (N) fertiliser has improved cereal yields on low-input farms in semi-arid Zimbabwe, the practice is reported to be laborious and time-consuming by farmers. In an effort to make micro-dosing less labour-intensive and more precise, an ammonium nitrate (AN) tablet, the equivalent of a micro-dose of prill AN (28 kg N ha−1) applied per maize plant, was developed by International Crops Research Institute for the Semi-Arid Tropics in collaboration with Agri-Seeds, Zimbabwe. This study characterized the physical stability, chemical (N% and solubility) and agronomic performance of AN tablets compared with prill AN. Only 10% of tablets broke when dropped from 2 m, showing that they are physically stable and can handle rough treatment. The N content in the tablets (33.3%) was comparable to that in prill AN (34.6%). However, the tablet formulation took twice as long to dissolve than prill AN when placed on a wet soil. Despite this difference in solubility, simple leaching column experiments suggest that less than 2% of the total AN applied was lost due to leaching. Agronomic trials were superimposed on the paired-plot demonstrations used to promote micro-dosing and the conservation agriculture tillage technique of planting basins from 2005 to 2008. Each tillage (plough and basins) plot was subdivided into three sub-plots on which no AN, prill AN and tableted AN treatments were superimposed. Maize was planted and management of plots was left to farmers. Micro-dosing with either prill or tableted AN significantly (p < 0.001) increased maize grain yield by over 40% in all seasons for planting basins. However, on the ploughed plot there was no yield benefit to using either AN formulation in the season with the lowest rainfall (2006–2007). There was no significant difference in grain yield and agronomic N use efficiency between prill and tableted AN formulations except for the 2005–2006 season in planting basins. During this season, in planting basins, tableted AN had significantly (p < 0.001) higher rainwater productivity than prill AN, which translated into greater grain yield. In addition, the maximum benefit to micro-dosing was observed to accrue when combined with water harvesting techniques such as planting basins. An observation supported by the host farmers, who in the second and third seasons chose to apply available basal soil fertility amendments to the basin plots over the flat plots. Thus, AN tablets if available at an affordable price can be used by smallholder farmers to more precisely apply N fertiliser. Future work should focus on the labour issues of micro-dosing, and making cost-effective tablets available to resource-poor farmers and also addressing other limiting soil nutrient

Weed growth and labor demand under hand-hoe based reduced tillage in smallholder farmers’ fields in Zimbabwe

Conservation agriculture based on hand hoe dug planting basins has been widely promoted for the last decade or two in the smallholder farming sector of southern Africa targeting resource constrained households without access to draft power. In Zimbabwe planting basins are used by about one hundred thousand households but on small plots (<0.5 ha) although most are unable to adopt soil surface mulching and crop rotation due to competing uses for crop residues as livestock feed and poorly developed markets for other crops, respectively. We report on the effects of reduced tillage based on hand-hoe dug planting basins (PB) on weed growth (20 farms), and labor demand and returns to investment (50 farms) compared with animal-drawn mouldboard plough based conventional tillage (CONV) in maize (Zea mays L.) fields, across selected districts located in contrasting agro-ecological zones in Zimbabwe. Weed growth was assessed through a survey conducted at the end of the 2009/10 and 2010/11 cropping seasons. Labor demand and returns to investment were measured on 50 farms across five districts using direct observations during the 2011/12 cropping season. The survey showed that farmers on average weeded their PB plots 2.7 times per season compared to 1.7–1.9 times in CONV plots (P < 0.001), and timing was often delayed in the former. Reduced tillage plots had 17% (P < 0.001) more weed ground cover and 9% (P < 0.05) more weed dry matter compared with CONV plots in the 2009/10 season, and differences in 2010/11 were not significant. Weed growth was highest in semi-arid areas (natural regions III and IV) compared with wetter sub-humid areas (natural region II) and arid areas (natural region V). Farmers planted their PB plots 12–23 days earlier, weeding frequency was 42.1–58.9% higher in PB plots, compared with CONV. Labor demand was more than double under PB (84.7 man days ha−1, weeding 48.1 man days ha−1) compared to CONV (38.6 man days ha−1). However, returns to investment were 42.7% higher under PB (U$1.77) compared with CONV (U$1.24). Weed growth and labor demand remained high under PB tillage even after several years, interventions such as the use of alternative weed control methods need to be introduced to farmers to reduce labor demand and consequently increase its adoption both in terms of number of farmers and cultivated area in southern Africa

Weed seed bank response to tillage and residue management in semi-arid Zimbabwe

The influence of conservation agriculture (CA) on weed ecology has been a concern to many researchers across the world and is the focus of this study in southern Africa. An experiment to look at the impacts of various tillage systems with different levels of crop residue on maize (Zea mays L.) was established in 2004/2005 season. The experiment was carried out at the International Crop Research Institute for the Semi-Arid Tropics (ICRISAT), Matopos Research Station, Zimbabwe. Three main tillage systems were compared, ripping tillage (RT), planting basins (PB) and conventional tillage (CT), with three different crop residue levels: 0, 4 and 8 tons ha−1. In 2007 soil samples were collected in the inter-row and in-row positions prior to tillage at 0–50 mm, 50–100 mm and 100–200 mm depths. The objective was to determine the effect of the treatment factors on weed seed bank species after three cropping cycles using the germination method. Nine major weed species were identified, with all the weeds unaffected by either tillage or mulching level. Eleusine indica, Corchorus tridens and Setaria species were the dominant weed species across all treatments. Setaria spp. was the dominant weed in the inter-row position of ripped plots. Although there was no significant individual treatment effect, there were significant (p < 0.05) interactions, with CT having reduced seed banks of Setaria spp. and E. indica compared to RT and PB. Percentage increases point to E. indica and Setaria spp. increasing under PB and RT compared to CT. C. tridens was significantly higher in PB compared to RT and CT in the 0–50 mm depth in the in-row position. This study probably coincided with the transition period in the weed bank succession process and needs to be repeated at a later date in the rotation. The majority of the weed species were not affected by any of the treatment combinations, a response attributed to plasticity of weeds to the tillage and residue level selection pressur

Micro Doses, Mega Benefits Promoting Fertilizer Use in Semi-Arid Zimbabwe

The contents of this document are (1) soil fertility and crop production in the smallholder systems, (2) current knowledge about fertilizer use in the dry areas of Zimbabwe, (3) low Input Options – microdosing, (4) what is microdosing? (5) types of N fertilizer available in Zimbabwe, (6) evidence of success from the drier areas of Zimbabwe, (7) how much fertilizer should a farmer buy? (8) where and how can farmers get fertilizer? (9) how sustainable is microdosing? (10) how can farmers maximize returns on their investment in fertility amendments? (11) introducing and Promoting Microdosing to Smallholder farmers, (12) training farmers in microdosing and (13) setting up demonstrations on microdosing

Effect of Conservation Agriculture on Maize Yield in the Semi-Arid Areas of Zimbabwe

Globally, a range of agronomic factors have been reported to have an impact on the performance of conservation agriculture (CA) and often determine its performance in relation to conventional agriculture (CONV). To assess this performance in Zimbabwe, 48 CA experiments were conducted by the International Crops Research Institute for the Semi-Arid Tropics in the semi-arid areas of southern Zimbabwe from 2004 to 2010, to calculate the weighted mean difference (WMD) through meta-analytical methods. The two CA practices, planting basins (Basins) and ripper tillage (Ripper), were compared with CONV. It was hypothesised that CA results improved yield compared with CONV and that the effect of CA practices on yield is affected by soil type, rainfall amount and distribution and selected management practices, which included rates of inorganic fertilisers and manures and mulching. Basins were superior to CONV in 59% of the experiments and the overall effect was significant (p < 0.001). The effect of Ripper was non-significant. The hypothesis that CA practices result in improved maize grain yield over CONV was accepted for Basins. The WMD for experiments conducted on sandy soils was 0.365 t ha−1 for Basins and 0.184 t ha−1 for Ripper, and in both cases was significant (p < 0.05). For clay soils, only the WMD for Basins was significant. A higher rainfall regime (500–830 mm) resulted in a lower WMD for Basins (0.095 t ha−1) and Ripper (0.105 t ha−1) compared with 0.151 t ha−1 for Basins and 0.110 t ha−1 for Ripper under lower rainfall (320–500 mm). The overall effect of Basins under the higher rainfall regime was not significant. There was better yield performance for Basins when the rainfall was well distributed; the reverse was noted for the Ripper. The application of 10–30 kg ha−1 of N (micro-dose range) resulted in a higher WMD for Basins than zero N application. Without N application, the WMD of Basins was not significant. For zero manure application in Basins, the WMD was 0.043 t ha−1 compared with 0.159 t ha−1 when manure was applied. The application of mulch depressed the WMD in Basins by 44% and Ripper by 89%. The hypothesis that yield performance under CA is influenced by soil type, rainfall amount and distribution, inorganic fertiliser and manure application was accepted

Exploring options for sustainable intensification in different farming system types of four Africa RISING countries

Sustainable intensification is proposed as a promising way to increase the productivity of agricultural systems while reducing pressure on ecosystems, safeguarding equitable relations among societal groups, and supporting the economic viability of households, enterprises, and communities. In sub-Saharan Africa, the identification and dissemination of options for sustainable intensification is hampered by the large diversity within and between farming systems, and their complexity arising from the interactions among different farm components and external factors. This study therefore uses an integrated farming systems approach to identify and assess context-specific improvements that can then be implemented and tested on-farm to foster experiential learning and facilitate adoption. We conducted a farming systems analysis for nine Africa RISING intervention sites across four countries, based on rapid and detailed farm characterizations, followed by model-supported diagnosis, and exploration of options for sustainable intensification. Farm diversity was described and analyzed by means of typologies and cross-site comparisons. Identified constraints varied depending on site and farming system type, but commonly included low input availability, climatic variability, poor soil fertility, sub-optimal livestock feeding, biotic stresses, and poor access to training and technical advice, all impairing farm productivity, returns to labor and capital inputs, income generation and food security. We investigated entry points that tackle the above constraints by exploring alternative farm configurations, technologies and practices for representative farms. By assessing potential impact of these changes on indicators beyond productivity, trade-offs were identified and assessed, for instance between profitability and household food self-sufficiency, and between nitrogen availability for crop uptake and increased nutrient losses. Taking a systems perspective during the entry point evaluation allowed differentiating potential effects on indicators at the field level versus the farm and household level. The exploration of options for specific farming system types now enables more targeted testing of promising innovations with farmers in the second project phase