Agro-ecological Zones Of Zimbabwe Research Articles

Fine-scale multi-temporal and spatial analysis of agricultural drought in agro-ecological regions of Zimbabwe

This study utilised multi-temporal satellite data to characterize droughts across the five Agro-ecological zones (AEZ) of Zimbabwe at monthly, seasonal, sub-seasonal and annual scales (2000 to 2018) using a combination of Satellite Pour l'Observation de la Terre (SPOT) Vegetation (VGT) and Project for On-Board Autonomy-Vegetation (PROBA-V) derived Vegetation Condition Index (VCI). The characterized droughts were validated, using maize yield and meteorological station derived Standardised Precipitation Index (SPI). The study showed differential spatial and temporal expression of drought in Zimbabwe, over the 19-year study period. November had the highest frequency of drought while the first quarter of the season experienced more droughts than the second quarter. Spatially, virtually all AEZ in Zimbabwe are prone to droughts and the frequency is increasingly, with the Agro-ecological region five (southern Zimbabwe) being the worst affected. Further, the study found a strong positive relationship between the VCI and maize yield (r = 0.701, P = 0.000), demonstrating the utility of the index in drought monitoring at national level. Overall, findings from this work highlight the significance of using multi-date and national-scale analysis of agricultural drought occurrence and trends. Moreover, this work provides critical baseline information for developing drought resilience and mitigation strategies in drought-prone areas.

Bio-competitive exclusion: efficacy of non-aflatoxigenic Aspergillus section Flavi-L morphotypes in control of aflatoxigenic Aspergillus flavus in groundnuts (Arachis hypogaea L.)

BackgroundThe biological control mechanism of Aspergillus flavus (aflatoxigenic) strains in groundnuts with atoxigenic strains from the same species through competitive exclusion employed the use of endemic and well-adapted strains within the agro-ecological zones of Zimbabwe. The selected elite non-aflatoxigenic isolates of A. flavus native to Zimbabwe were evaluated for their capability to reduce aflatoxin contamination in groundnuts under laboratory conditions.ResultsAverage reduction percentages in aflatoxin B concentration for the 2019 and 2020 set of experiments ranged from 91.6 ± 3.4 to 95.8 ± 3.1% and 90.29 ± 3.6% to 95.29 ± 4.1%, respectively. Levels of aflatoxin in the co-inoculation research experiments administered were significantly reduced in all the experimental units carried out. Treatment efficiencies of the tested isolates in this study at 4:1 and 2:1 ranged from 1.20 to 2.52 and from 1.02 to 1.21, respectively. The efficacy of the tested non-aflatoxigenic strains against the aflatoxigenic strain native to Zimbabwe (ZMW 0127) indicates that the non-aflatoxigenic isolates of A. flavus. have sound practical applications against vast communities of aflatoxin-producing fungi across all the agro-ecological zones in Zimbabwe.ConclusionThe recognized non-aflatoxigenic isolates will be of an incentive as dynamic active ingredients in biocontrol formulations for the decrease in aflatoxins in groundnuts grown in Zimbabwe.

The 5As: assessing access to animal-drawn conservation agriculture planting equipment by smallholder farmers

Conservation agriculture is a global response to rampant land degradation, soil nutrient mining, declining crop yields and climate change and variability in southern Africa. In Zimbabwe, digging of planting basins is the main archetype of conservation agriculture practiced by a majority of smallholder farmers. Yet, a majority of smallholder farmers have complained about the labour demand of this typology of conservation agriculture, particularly at planting. Access to animal-drawn CA planting machinery may reduce the labour burden of the technology. However, there is paucity of the literature addressing the non-socio-demographic determinants of access to animal-drawn CA planting equipment in Zimbabwe. Therefore, the objective of this study was to evaluate access to animal-drawn CA planting equipment by smallholder farmers in Chivi, Murehwa and Mutoko districts located in different agro-ecological zones of Zimbabwe using the 5As framework of access: acceptability, accessibility, affordability, awareness and availability. Data were collected through a household questionnaire, which was triangulated with focus group discussions, key informant interviews and personal observations. The significant non-socio-economic access to animal-drawn CA planting machinery factors was: acceptability, accessibility, affordability and availability (mean scores of 1.32, 1.44, 1.90 and 1.36, respectively). We recommend the provision of monetary incentives to farmers practicing conservation agriculture. Such incentives have to be based on amount of carbon sequestered and should solely be used for the purchase of conservation agriculture equipment.

Efficacy of metal silos and hermetic bags against stored-maize insect pests under simulated smallholder farmer conditions

Pesticide-free hermetic grain storage is an environmentally-benign alternative to synthetic pesticides, currently being used in many countries. However, in some African countries knowledge gaps exist on the effectiveness of hermetic maize storage, particularly where the Larger Grain Borer (LGB), Prostephanus truncatus occurs. Trials simulating African smallholder farmer conditions were conducted at two sites in contrasting agro-ecological zones in Zimbabwe for up to 12 months during the 2013/14 storage season. There were two hermetic treatments: metal silos and hermetic bags; and two non-hermetic treatments: a registered synthetic pesticide and untreated control, in polypropylene bags. Two modes of infestation: natural and combined (natural plus artificial) were used as factors. Treatments were arranged in a completely randomised design and stored in ordinary rooms. Hermetic treatments were significantly superior (P < 0.001) to non-hermetic treatments in preserving germination, controlling insect population development, suppressing maize grain damage, controlling grain dust production and consequently limiting weight loss during storage. Hermetic bags were more effective than non-hermetic treatments in reducing storage losses despite the plastic liners having multiple insect-induced perforations of more than 300 holes per plastic liner at termination. However, there were no significant differences between metal silos and hermetic bags regardless of the mode of infestation. There was strong correlation between total insect population per kg and: percentage grain damage, percentage weight loss, and grain dust which indicate the importance of controlling insect pest development during storage to reduce losses. Results show that hermetic storage can be an effective pesticide-free alternative to synthetic pesticides in reducing grain storage losses under smallholder farming conditions, even where LGB occurs.

Evaluation of the performance of sorghum genotypes using GGE biplot

Gasura, E., Setimela, P. S. and Souta, C. M. 2015. Evaluation of the performance of sorghum genotypes using GGE biplot. Can. J. Plant Sci. 95: 1205–1214. In spite of sorghum's drought tolerance, it is largely affected by genotype×environment interaction (GE), making it difficult and expensive to select and recommend new sorghum genotypes for different environments. The objectives of this study were to examine the nature of GE for sorghum grain yield, to identify superior sorghum genotypes for sorghum production environments and determine ideal testing locations for future breeding activities in Zimbabwe. The grain yield of 20 sorghum genotypes from Seed Co. Pvt. Ltd. were evaluated for 2 yr (2011/2012 and 2012/2013 cropping seasons) at five locations in different agro-ecological zones of Zimbabwe. Combined analyses of variance showed significant differences for genotypes (P&lt;0.01), environments (P&lt;0.001) and genotype×location (P&lt;0.01). Genotype×environment variance component was seven times greater than that of genotypes. Genotype×environment interaction was attributed to the variability in the predictable biotic and abiotic factors associated with the different locations. The genotype main effect plus GE biplot showed that the experimental sorghum genotypes W07, W09, W05, G06 and OP46 were high yielding and stable, and possessed other desirable agronomic traits. The most discriminating and representative location was Rattray Arnold Research Station.

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 (<0.5ha) 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 (84.7mandaysha−1, weeding 48.1mandaysha−1) compared to CONV (38.6mandaysha−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.

Effect of hand-hoe based conservation agriculture on soil fertility and maize yield in selected smallholder areas in Zimbabwe

Conservation agriculture (CA) based on hand-hoe prepared planting basins is being widely promoted in southern Africa, targeting resource-constrained farmers with limited access to draft power. This study was conducted across 15 districts covering four agro-ecological zones in Zimbabwe where paired CA and conventional animal drawn tillage (CADT) plots had been established on 450 farms as part of CA promotion. The aim of the study was to assess the effect of CA on soil pH, organic C, total P and maize (Zea mays L.) grain yield compared with CADT, and also to evaluate the yield benefits of mulching and crop rotation in CA with or without mineral fertilizer use. It was hypothesized that CA improved the pH, organic C, total P of the soils (Arenosols) and grain yield compared with CADT and that mulching and crop rotation in CA increased maize grain yield. A total of 1014 soil samples (0–0.2m depth) were taken at the end of the 2009/10 cropping season and analyzed for pH, organic C and total P. Grain yield was determined in 2009/10 and 2010/11 from 0.01ha net plots. There was no significant difference in average soil pH, total P and organic C between CA and CADT plots and therefore the hypothesis that CA improves these soil properties was rejected. Average concentration for organic C for both CA and CADT plots was less than 10gkg−1, a minimum threshold for well managed soils. When combined with mineral fertilizer: mulching, crop rotation, and mulching+crop rotation in CA increased maize grain yield by 20–33%, 7–9% and 58–69%, respectively. With no mineral fertilizer application, mulching, crop rotation, and mulching+crop rotation depressed maize grain yield by 48%, 28% and 36%, respectively. Therefore the hypothesis that mulching and crop rotation increase maize grain yield was accepted when mineral fertilizer was added and rejected when the fertilizer was not added. It was concluded that the yield benefits of CA can only be realized when mineral fertilizer is also applied. All the three CA principles in combination with mineral fertilizer results in highest yield benefits compared with one or two principles as currently done by most smallholder farmers in Zimbabwe. Access to mineral fertilizer is an important factor in the targeting of CA promotion in smallholder areas of Zimbabwe and similar socio-ecological zones in sub-Saharan Africa.

Effect of farmer management strategies on spatial variability of soil fertility and crop nutrient uptake in contrasting agro-ecological zones in Zimbabwe

Variability of soil fertility within, and across farms, poses a major challenge for increasing crop productivity in smallholder systems of sub- Saharan Africa. This study assessed the effect of farmers' resource endowment and nutrient manage- ment strategies on variability in soil fertility and plant nutrient uptake between different fields in Gokwe South (ave. rainfall *650 mm year -1 ; 16.3 per- sons km -2 ) and Murewa (ave. rainfall *850 mm year -1 ; 44.1 persons km -2 ) districts, Zimbabwe. In Murewa, resource-endowed farmers applied manure ((3.5 t ha -1 year -1 ) on fields closest to their home- steads (homefields) and none to fields further away (outfields). In Gokwe the manure was not targeted to any particular field, and farmers quickly abandoned outfields and opened up new fields further way from the homestead once fertility had declined, but homefields were continually cultivated. Soil available P was higher in homefields (8-13 mg kg -1 ) of resource-endowed farmers than on outfields and all fields on resource constrained farms (2-6 mg kg -1 ) in Murewa. Soil fertility decreased with increasing distance from the homestead in Murewa while the reverse trend occurred in Gokwe South, indicating the impact of different soil fertility management strategies on spatial soil fertility gradients. In both districts, maize showed deficiency of N and P, implying that these were the most limiting nutrients. It was concluded that besides farmers' access to resources, the direction of soil fertility gradients also depends on agro-ecological conditions which influence resource management strategies.

Mitochondrial DNA D‐loop sequences suggest a Southeast Asian and Indian origin of Zimbabwean village chickens

This study sought to assess mitochondrial DNA (mtDNA) diversity and phylogeographic structure of chickens from five agro-ecological zones of Zimbabwe. Furthermore, chickens from Zimbabwe were compared with populations from other geographical regions (Malawi, Sudan and Germany) and other management systems (broiler and layer purebred lines). Finally, haplotypes of these animals were aligned to chicken sequences, taken from GenBank, that reflected populations of presumed centres of domestication. A 455-bp fragment of the mtDNA D-loop region was sequenced in 283 chickens of 14 populations. Thirty-two variable sites that defined 34 haplotypes were observed. In Zimbabwean chickens, diversity within ecotypes accounted for 96.8% of the variation, indicating little differentiation between ecotypes. The 34 haplotypes clustered into three clades that corresponded to (i) Zimbabwean and Malawian chickens, (ii) broiler and layer purebred lines and Northwest European chickens, and (iii) a mixture of chickens from Zimbabwe, Sudan, Northwest Europe and the purebred lines. Diversity among clades explained more than 80% of the total variation. Results indicated the existence of two distinct maternal lineages evenly distributed among the five Zimbabwean chicken ecotypes. For one of these lineages, chickens from Zimbabwe and Malawi shared major haplotypes with chicken populations that have a Southeast Asian background. The second maternal lineage, probably from the Indian subcontinent, was common to the five Zimbabwean chicken ecotypes, Sudanese and Northwest European chickens as well as purebred broiler and layer chicken lines. A third maternal lineage excluded Zimbabwean and other African chickens and clustered with haplotypes presumably originating from South China.

Variation in village chicken production systems among agro-ecological zones of Zimbabwe

The degree to which village chickens are integrated in the smallholder farming systems differs depending on the socio-economic, cultural and biological factors within each system. The objective of this study was to characterise the village chicken farming systems and identify possible threats to, and opportunities for, local chickens in the agro-ecological zones of Zimbabwe. A pre-tested questionnaire was administered to households randomly selected from five districts, Risitu (n=97), Hurungwe (n=56), Gutu (n=77), Gokwe-South (n=104) and Beitbridge (n=37) in eco-zones I-V, respectively. Age of head of household averaged 47 years (SD = 14.3). Land holdings per household averaged 4.82 ha (SD = 3.6). Overall, 17.7 percent of the households ranked livestock as the major source of income compared to 70.8 percent who ranked crops as the main contributor. Chicken flock size averaged 16.7 (SD = 12.4), and the highest flock sizes were observed in eco-zones I and IV. Households owning cattle, goats and other livestock assigned less important ranks to chickens. Chickens were usedmainly for the provision of meat and eggs whilst the use of chicken feathers and investment were uncommon practises. Results indicate that more support is necessary for village chickens in the non-cropping regions of the country.

Absence of population substructuring in Zimbabwe chicken ecotypes inferred using microsatellite analysis

The objective of this study was to investigate the population structure of village chickens found in the five agro-ecological zones of Zimbabwe. Twenty-nine microsatellites were genotyped for chickens randomly selected from 13 populations, including the five eco-zones of Zimbabwe (n = 238), Malawi (n = 60), Sudan (n = 48) and six purebred lines (n = 180). A total of 280 alleles were observed in the 13 populations. Forty-eight of these alleles were unique to the Zimbabwe chicken ecotypes. The average number (+/-SD) of alleles/locus was 9.7 +/- 5.10. The overall heterozygote deficiency in the Zimbabwe chickens (F(IT) +/- SE) was 0.08 +/- 0.01, over 90% of which was due to within-ecotype deficit (F(IS)). Small Nei's standard genetic distances ranging from 0.02 to 0.05 were observed between Zimbabwe ecotypes compared with an average of 0.6 between purebred lines. The structure software program was used to cluster individuals to 2 </= K </= 7 assumed clusters. The most probable clustering was found at K = 6. Ninety-seven of 100 structure runs were identical, in which Malawi, Sudan and purebred lines split out as independent clusters and the five Zimbabwe ecotypes clustered into one population. The within-ecotype marker-estimated kinships (mean = 0.13) differed only slightly from the between-ecotype estimates. Results from this study lead to a rejection of the hypothesis that village chickens are substructured across agro-ecological zones but indicated high genetic diversity within the Zimbabwe chicken population.

Nutrient use efficiencies and crop responses to N, P and manure applications in Zimbabwean soils: Exploring management strategies across soil fertility gradients

The spatial variability in crop yields commonly observed in smallholder farms of sub-Saharan Africa is often caused by gradients of declining soil fertility with increasing distance from the homestead. This heterogeneity means that recommendations based on regional soil surveys are of limited value. The variability in soil qualities within farms must be considered when designing management strategies, and their feasibility analysed by integrating results at the farm livelihood scale. For this purpose, we have developed the model FARMSIM, a dynamic bio-economic model for analysis and exploration of trade-offs in resource and labour allocation in heterogeneous smallholder farms. Focusing on farm-scale strategies, the approach to simulation of soil and crop processes in FARMSIM (the sub-model FIELD) is designed to be simple, but to keep the necessary degree of complexity to capture heterogeneity in resource use efficiencies. To test our approach, the sub-model FIELD was calibrated against chronosequences of woodland clearance in three agroecological zones of Zimbabwe (with soil textures of 3, 10, 35% clay), and used to simulate: (i) the creation of soil fertility gradients, and (ii) different strategies of N, P and manure applications to maize and soyabean rotations in homefields and outfields of smallholder farms on clayey and sandy soils. The results of the simulation of management strategies were tested against on-farm experimental data from Murewa, Zimbabwe. The model produced satisfactory predictions ( r 2: 0.6–0.9) of long-term changes in soil organic C, of crop responses to N and P and of nutrient use efficiencies across a wide range of yields and different field types. This demonstrated the broad applicability of the model despite the sparse data required for initialisation. However, the model results were less accurate in predicting crop responses to N and P applications in the outfields on sandy soils. Experimental evidence indicated yield limitation by Ca and Zn deficiencies in highly depleted outfields on sandy soils, which were not included mechanistically in the current version of FIELD. Repeated applications of 16 t ha −1 year −1 of manure allowed larger responses to applied N and P after 3 years of experimentation; such a corrective effect of manure was simulated to be due to improved N and P recovery efficiencies in the model. In combination with the experimental data, the simulation results suggested that soil fertility gradients affect nutrient use efficiencies, operating mostly on the efficiencies of nutrient capture rather than conversion. A typology of fields according to the type of management interventions needed is introduced, based on a generic application of FIELD with this parameterisation.

Evaluation of first planting dates recommended by criteria currently used in Zimbabwe

This paper presents a method for evaluating criteria used to advise farmers on planting dates at the onset of the rainy season. The criteria were evaluated using an analysis of the relative transpiration rate (the ratio of the actual transpiration to the potential transpiration) over a 30-day period following sowing (initial growth stage) by means of a soil water balance model (BUDGET). Crop failure or a false start to the season was indicated by a relative transpiration rate of less than 35% over the 30 days. The first recommended planting dates have been identified for a number of stations in the six agro-ecological zones of Zimbabwe and for the last 30 years, using three different criteria. The criteria included two, which are currently utilized in Zimbabwe: the AREX criterion of the Agricultural Research Extension (25 mm rainfall in 7 days) and the MET criterion of the Department of Meteorological Services (40 mm in 15 days). A third criterion, DEPTH (40 mm in 4 days), based on farmers practices, is introduced in this paper. In general, for all agro-ecological zones, the earliest planting dates were found with the AREX criterion. Those generated by the MET criterion are typically 7–10 days later. The planting dates generated by the DEPTH criterion are some 2–3 weeks later than the AREX dates. The evaluation revealed that in non-failure years, the relative transpiration rate over the 30 days is about 70% for all criteria and for all zones. However, the risk a farmer runs of a false start when applying the AREX criterion is unacceptably high (1 year out of 2). Applying the MET criterion reduces the failures to 2 years out of 5 and when the DEPTH criterion is applied, the probability of failure drops to 1 year out of 4.

Soil fertility replenishment through agroforestry systems in two contrasting agro-ecological zones of Zimbabwe.

The main limiting nutrient in most communal areas of Zimbabwe is nitrogen (N). There is also deterioration of soil physical properties without continual addition of organic matter to the soil. Soil fertility replenishment through agroforestry technologies such as biomass transfer and improved fallows are discussed in terms of their potential to alleviate N limitations to increase maize yield. Various management practices to enhance the nutrient use efficiency on these systems are discussed. Areas of future resources are suggested. Transactions of the Zimbabwe Scientific Association Volume 72 (Supplement) 1998, pp. 31-42