Smallholder Farming Areas Of Zimbabwe Research Articles

Evaluation of different rainwater harvesting techniques for improved maize productivity in semi‐arid regions of Zimbabwe with sandy soils

AbstractBackgroundMaize production in semi‐arid areas has been hindered by moisture stress and poor soil fertility. Long frequent droughts and shortening of growing seasons have been causing yield reduction. Limited knowledge of soil water management by farmers is another key contributor to poor maize yields in the smallholder sector. Therefore, the objective of the study was to investigate the effects of contour‐based and field‐based water harvesting technologies on maize grain yield and rainwater use efficiency under rain‐fed conditions on three farms (Jera, Kudzeeta and Manjengwa) with sandy soils in the Marange smallholder farming area of Zimbabwe. The experiment was laid out as a split plot in a randomised complete block design with three replications at each site. Contour‐based rainwater harvesting structures were the main treatments comprising tied contour (TC), standard contour (STDC) and infiltration pits (IP). Field‐based rainwater harvesting structures were the subplot treatments comprising tied ridges (TR), pot holing (PH) and the flat system (FLAT).ResultsResults showed that the contour‐based water harvesting structures significantly influenced (p < 0.05) maize grain yields. TCs had the highest maize grain yields compared with infiltration pits and STDCs over two cropping seasons. Maize yields on field‐based TR were significantly higher (p < 0.05) than on the FLAT but were not different (p > 0.05) with what was obtained on PH. The combination of TC and TR water harvesting technologies resulted in significantly higher maize yields (p < 0.05) than other combinations. TR and STDC also gave higher maize grain yield at Jera farm which was significantly different from other two farms. Rainwater use efficiency followed the same trend as maize grain yields, with TC having higher values but not significantly different (p > 0.05) from STDC.ConclusionIt can be concluded that farmers in semi‐arid areas adopt a combination of TC with either TR or PH to improve rainwater use efficiency and maize yields.

Effect of contour rainwater-harvesting and integrated nutrient management on sorghum grain yield in semi-arid farming environments of Zimbabwe

ABSTRACT The application of insufficient amounts of mineral fertiliser, coupled with unreliable precipitation, has caused a drastic reduction in the yield of sorghum in the smallholder-farming areas of Zimbabwe. This calls for innovative interventions to improve production under changing climatic conditions. This study evaluated the effect of contour-based rainwater-harvesting methods and the use of cattle manure + N nutrient amendment on sorghum yield. A split-split plot experiment was conducted where rainwater-harvesting practice, sorghum variety, cattle manure + N and distance from rainwater-harvesting structure were treatment factors. The results showed that the yield of sorghum was significantly higher under the tied contour and infiltration pits than standard contour at all distances from rainwater-harvesting practices and seasons. In all seasons sorghum varieties Macia and Sc Sila showed higher yield under the tied contour and infiltration pits than standard contour. However, regardless of the distance from rainwater-harvesting practice and season the sorghum variety, Macia showed a higher grain yield than Sc Sila. At each incremental level of N application to cattle manure, Macia had a higher grain yield than Sc Sila, and no significant grain yield benefits were shown in each variety at N application to cattle manure above 50 kg N ha−1.

Effectiveness of hermetic maize grain storage technology in limiting aflatoxin exposure in women and children from smallholder farming areas

The longitudinal study assessed the effectiveness of hermetic storage technology in limiting aflatoxin exposure among women aged 15-45 years and children under five years of age from households in selected smallholder farming areas of Zimbabwe. Exposure levels were determined by measuring aflatoxin M1 (AFM1) in urine samples from women and children every three months during the 2015/2016 storage season for nine months. After extraction and immunoaffinity column clean up, AFM1 was determined by high performance liquid chromatography. Generally, the proportion of AFM1 positive urine samples from women increased throughout the grain storage season from 5.4% (n=23) (geometric mean (GM) 1.62 μg/l) at harvest to 75% (n=315) (GM 48.35 μg/l) nine months later (range <limit of quantification (LOQ)-217.29 μg/l). In urine samples from children, AFM1 positive samples increased from 2.2% (n=4) (GM 0.78 μg/l) at harvest to 72.5% (n=98) (GM 22.81 μg/l) nine months later (range <LOQ- 135.00 μg/l). Urinary AFM1 was significantly higher in samples from participants using conventional storage (GM 62.28 μg/l; range <LOQ-217.29 μg/l) compared with samples from participants using hermetic technology (GM 31.95 μg/l; range <LOQ-157.71 μg/l. There was no significant difference in AFM1 concentrations in urine samples from participants consuming grain from metal silos and hermetic bags (P>0.05) hence the two technologies are equally effective in limiting exposure to aflatoxins in humans. The study concluded that aflatoxin exposure levels among women and children from small-holder farming areas increase throughout the postharvest season and the use of hermetic storage technology resulted in up to 33.2% decrease in frequency of detection and 48.7% decrease in levels of AFM1 compared to conventional storage technologies. Thus hermetic grain storage can be an effective technology recommended for limiting aflatoxin exposure in smallholder farming populations.

Performance of Two Rape (Brassica napus) Cultivars under Different Fertilizer Management Levels in the Smallholder Sector of Zimbabwe

Crop response to fertilizer application depends on the physiological and morphological characteristics of the cultivars, thus causing cultivar differences in growth rate and final yield. A study was carried out in the Zvimba smallholder farming area of Zimbabwe, from November 2016 to February 2017, to investigate the performance of two rape (Brassica napus) cultivars under different nitrogen fertilizer management levels. An experiment was set up in a randomized complete block design, replicated three times, with two rape varieties, Hobson and English Giant, and 5 ammonium nitrate (AN) (34.5% N) fertilizer application rates (200 kg/ha, 300 kg/ha, 350 kg/ha, and 400 kg/ha) as factors. Nitrogen fertilizer rates had a significant (p<0.05) effect on leaf length at 6 WAP and 7 WAP. Nitrogen fertilizer application levels had significant effects on both in-season and total fresh leaf yield. There were no varietal effects on the leaf length (p>0.05), in-season yield and total leaf yield (p>0.05), and there were also no variety ∗ fertilizer application level interaction effects on leaf length, in-season yield and total leaf yield (p>0.05). From the results of this study, English Giant rape would maintain a longer leaf length than Hobson up to the end of the season, but the two cultivars have similar yield response to fertilizers’ application rate. Both the English Giant rape and Hobson rape cultivars can, therefore, be recommended for production in the Mhondoro smallholder farming area of Zimbabwe and other areas with similar climatic and soil characteristics.

Velvet Bean and Cowpea Residual Effects on Maize Crop in Smallholder Farming Areas of Zimbabwe

On-farm research was conducted in Dendenyore Communal Land and Zana Resettlement areas of Hwedza District, Zimbabwe from 1999 to 2001. The objective of the study was to evaluate the effects of velvet bean and cowpea on growth and yield of maize in legume-maize rotation system. A total of 14 treatments, which consisted of forage legume and maize crops were examined. The experiment was established in a randomized complete block design with 9 replicates. On-farm sites were the replicates. The results show a significant residual effect of velvet bean and cowpea, when grown with single super phosphate fertiliser, on the maize stover and grain yield. They indicate significant phosphorus residual effects on a subsequent maize crop on sandy soils. Forage legumes contribute to residual soil fertility in fallen leaves and roots that increases yield of subsequent crops. The results also reveal that biomass production in perennial leys, grazed during the dry season, would be greater in the second season than in the establishment year. The results also indicate that in the velvet bean systems, especially green manure, nitrogen is lost very early in the season. This may lead to lack of synchrony between nutrient availability and crop uptake. The maize after green manure system had a nitrogen use efficiency of about 11 kg/kg of nitrogen applied. These results show the residual potential of forage legumes in reducing nitrogen fertiliser need for subsequent maize crops in mixed livestock-cropping systems.

Maize Water Productivity and Its Relationship to Soil Properties under Integrated Cattle Manure and Mineral‐Nitrogen Fertilizer in a Smallholder Cropping System

Crop water productivity is often regarded as indicating the water use efficiency of crops, an important aspect, particularly under erratic rainfall conditions. This study investigated the effects of cattle manure and mineral‐N fertilizer application on maize (Zea mays L.) water productivity (MWP) on clay and sandy soils in a smallholder farming area of Zimbabwe. Four fields previously exhibiting heterogeneous fertility were managed under the following treatments: control (no amendment) and cattle manure (5, 15, and 25 Mg ha−1) + 100 kg ha−1 mineral‐N fertilizer for 7 yr. Thereafter, the effects of fertility treatment on MWP were expressed as actual maize grain yield produced per unit of seasonal transpiration modeled using AquaCrop. Furthermore, the relationship of MWP to physical soil properties was determined using principal component analysis. The MWP significantly (P < 0.05) improved with an increase in cattle manure plus mineral‐N fertilizer application over control on both soils ranging between 0.5 and 1.7 kg m−3 and between 0.24 and 1.1 kg m−3 on clay and sandy soils, respectively. The MWP was significantly correlated (P < 0.05) with the steady‐state infiltration rate on the clay soil and with soil organic C on the sandy soil. We concluded that cattle manure and mineral‐N fertilizer application is key to MWP improvement in rainfed smallholder cropping systems and is closely coupled with improvements in physical soil properties on clay soil than sandy soil. Therefore, the observations attest to the importance of site‐specific management that could contribute to efficient resource use in resource‐constrained farming areas.

Ethnoveterinary plants and practices used for ecto-parasite control in semi-arid smallholder farming areas of Zimbabwe.

BackgroundThe inclusion of traditional plant-based ecto-parasite control methods in primary health care of livestock is increasingly becoming an important intervention for improving livestock productivity in resource-challenged smallholder farming areas. In this study, commonly used plants used for the control of cattle ticks and other pests were identified through a survey in four semi–arid districts of Zimbabwe.MethodsA standard structured questionnaire with details of demographics, socioeconomic status of households, livestock parasites, control practices and list of ethnoveterinary plants used was used to interview 233 knowledgeable smallholder farmers in four districts. Focus group discussions with community members further provided insights on how the plants were being used and other issues surrounding ecto-parasite control and indigenous knowledge systems in the study areas.ResultsThe older generation (>40 years) of the respondents were knowledgeable about ethnoveterinary plants and practices. Overall, 51 plant species were reportedly effective against cattle ticks and other livestock parasites. The most frequently mentioned plants were in descending order, Cissus quadrangularis (30.1%), Lippia javanica (19.6%), Psydrax livida (14.9%) and Aloe sp (14.9%). Most of the plant materials were prepared by crushing and soaking in water and spraying the extract on animals. Despite the knowledge of these useful pesticidal plants, the preferred animal health care for cattle and other highly ranked livestock species is still the use of commercial acaricides. Cattle dipping services were reported sporadic by 48% of the respondents. Traditional knowledge and plants are considered only as an alternative in the absence of conventional synthetic products.ConclusionsLivestock farming communities know of plant species used for livestock ecto-parasite control. The plant species are mostly used to complement commercial products. More work, is required to confirm the acaricidal properties claimed by the farmers in order to optimize and promote sustainable use of these plants.

Cattle manure and inorganic nitrogen fertilizer application effects on soil hydraulic properties and maize yield of two soils of Murewa district, Zimbabwe

AbstractThis study set out to determine the effects of cattle manure and inorganic N‐fertilizer application on the hydraulic properties and maize yield of a clay and sandy soil in a smallholder farming area of Zimbabwe. Four fields classified as homefields (HF: more fertile and closer to homesteads) and outfields (OF: less fertile and further from the homesteads) were selected on clay and sandy soil. They were subjected to four treatments, control (no fertility amendment), 5, 15 and 25 t/ha cattle manure + 100 kg/ha N (as ammonium nitrate) for 7 years. A two‐way randomized complete block design was used with fertility and field type as the two factors. Clay soil hydraulic properties, which included density of macropores with a diameter >300 μm, unsaturated hydraulic conductivity, steady‐state infiltration rate, moisture retention under low suction and maize grain yield, were significantly improved (P < 0.05) by fertility management compared with the control and were generally comparable between the HF and OF. Fertility management significantly improved maize grain yield on sandy soils but did not enhance hydraulic parameters, thereby indicating poor responsiveness in structural build‐up. On the other hand, significantly different hydraulic parameters between the sandy soil HF and OF suggested effects of other factors not related to soil fertility and field type treatments. We therefore concluded that application of a high rate (25 t/ha) of cattle manure and inorganic N‐fertilizer is beneficial for fertility restoration to the degraded OFs with associated comparable hydraulic properties on HFs and OFs on clay soil, unlike on sandy soil.

Influence of basin‐based conservation agriculture on selected soil quality parameters under smallholder farming inZimbabwe

AbstractThe research was carried out to determine the effect of basin‐based conservation agriculture (CA) on selected soil quality parameters. Paired plots (0.01 ha) ofCAand conventional tillage based on the animal‐drawn mouldboard plough (CONV) were established between 2004 and 2007 on farm fields on soils with either low (12–18% – sandy loams and sandy clay loams) or high clay levels (>18–46% – sandy clays and clays) as part of an ongoing project promotingCAin six districts in the smallholder farming areas of Zimbabwe. We hypothesized thatCAwould improve soil organic carbon (SOC), bulk density, aggregate stability, soil moisture retention and infiltration rate. Soil samples forSOCand aggregate stability were taken from 0 to 15 cm depth and for bulk density and soil moisture retention from 0 to 5, 5 to 10 and 10 to 15 cm depths in 2011 from maize plots. LargerSOCcontents,SOCstocks and improved aggregate stability, decreased bulk density, increased pore volume and moisture retention were observed inCAtreatments. Results were consistent with the hypothesis, and we conclude thatCAimproves soil quality under smallholder farming. Benefits were, however, greater in high clay soils, which is relevant to the targeting of practices on smallholder farming areas of sub‐Saharan Africa.

Optimizing dambo (seasonal wetland) cultivation for climate change adaptation and sustainable crop production in the smallholder farming areas of Zimbabwe

Most smallholder farming areas of Zimbabwe have low soil fertility and low rainfall, which has continually decreased over the past years. In recent years, most of the smallholder farming areas have experienced perennial droughts, poor rainfall distribution and crop failures and these have been attributed to climate change and variability. Cultivation of dambos, which are seasonal wetlands, presents a climate change and variability adaptation option for smallholder farmers. This synthesis analyses the role of dambo cultivation in climate change and variability adaptation and discusses future directions for sustainable dambo utilization. The data on current dambo farming practices were collected from literature, surveys and field observations. The results showed that farmers grow crops in dambos as an adaptive strategy to climate change and variability and have largely abandoned upland fields where yields are <1 t ha−1 in preference of dambos where yields average 2–3 t ha−1. Dambo cultivation offers a buffer against crop failures and has resulted in improved household food security. We conclude that dambo cultivation is a potentially beneficial farmer-driven climate change and variability adaptation strategy. However, if not properly designed and managed, dambo cultivation may result in their degradation hence there is need for further research to evaluate options for sustainable dambo utilization as intensification of dambo agriculture is important for food security.

Pushing the envelope? Maize production intensification and the role of cattle manure in recovery of degraded soils in smallholder farming areas of Zimbabwe

Soil fertility decline is a major constraint to crop productivity on smallholder farms in Africa. The objective of this study was to evaluate the long-term (up to nine years) impacts of nutrient management strategies and their local feasibility on crop productivity, soil fertility status and rainfall infiltration on two contrasting soil types and different prior management regimes in Murehwa, Zimbabwe. The nutrient management strategies employed in the study were: a control with no fertiliser, amendments of 100kg Nha−1, 100kg N+lime, three rates of manure application (5, 15 and 25tha−1) in combination with 100kg Nha−1, and three rates of P fertiliser (10, 30 and 50kg Pha−1) in combination with 100kg N, 20kg Ca, 5kg Zn and 10kg Mnha−1. Maize grain yields in sandy soils did not respond to the sole application of 100kg Nha−1; manure application had immediate and incremental benefits on crop yields on the sandy soils. A combination of 25tha−1 manure and 100kg N gave the largest treatment yield of 9.3tha−1 on the homefield clay soils, 6.1tha−1 in the clay outfield, 7.6tha−1 in the homefield and 3.4tha−1 in the eighth season. Yields of the largest manure application on the sandy outfields were comparable to yields with 100kg N in combination with 30kg P, 20kg Ca, 5kg Zn and 10kg Mnha−1 in the homefields suggesting the need to target nutrients differently to different fields. Manure application improved rainfall infiltration in the clay soils from 21 to 31mmh−1 but on the sandy soils the manure effect on infiltration was not significant. Despite the large manure applications, crop productivity and SOC build-up in the outfield sandy soils was small highlighting the difficulty to recover the fertility of degraded soils. The major cause of poor crop productivity on the degraded sandy soils despite the large additions of manure could not be ascertained. The current practice of allocating manure and fertiliser to fields closest to homesteads exacerbates land degradation in the sandy outfields and increases soil fertility gradients but results in the most harvest for the farm. On clay soils, manure may be targeted to outfields and mineral fertiliser to homefields to increase total crop productivity. Farmers who owned cattle in the study site can achieve high manure application rates on small plots, and manure application can be rotated according to crop sequences. Consistent application of manure in combination with mineral fertilisers can be an effective option to improve crop yield, SOC and moisture conservation under smallholder farming conditions. Combined manure and mineral fertiliser application can be adapted locally as a feasible entry point for ecological intensification in mixed crop–livestock systems.

Opportunities for optimization of in-field water harvesting to cope with changing climate in semi-arid smallholder farming areas of Zimbabwe

Climate change has resulted in increased vulnerability of smallholder farmers in marginal areas of Zimbabwe where there is limited capacity to adapt to changing climate. One approach that has been used to adapt to changing climate is in-field water harvesting for improved crop yields in the semi- arid regions of Zimbabwe. This review analyses the history of soil and water conservation in Zimbabwe, efforts of improving water harvesting in the post independence era, farmer driven innovations, water harvesting technologies from other regions, and future directions of water harvesting in semi arid marginal areas. From this review it was observed that the blanket recommendations that were made on the early conservation method were not suitable for marginal areas as they resulted in increased losses of the much needed water. In the late 1960 and 70s’, soil and water conservation efforts was a victim of the political environment and this resulted in poor uptake. Most of the water harvesting innovations which were promoted in the 1990s’ and some farmer driven innovations improved crop yields in marginal areas but were poorly taken up by farmers because they are labour intensive as the structures should be made annually. To address the challenges of labour shortages, the use of permanent in-field water harvesting technologies are an option. There is also need to identify ways for promoting water harvesting techniques that have been proven to work and to explore farmer-led knowledge sharing platforms for scaling up proven technologies.

Greenhouse Gas Emissions from Intermittently Flooded (Dambo) Rice under Different Tillage Practices in Chiota Smallholder Farming Area of Zimbabwe

Agriculture is one of the biggest sources of greenhouse gases. Rice production has been identified as one of the major sources of greenhouse gases, especially methane. However, data on the contributions of rice towards greenhouse gas emissions in tropical Africa are limited. In Zimbabwe, as in most of Sub-Saharan Africa, there are very few studies that have explored greenhouse gas emissions from agricultural lands. This study reports the first dataset on greenhouse gas emissions from intermittently flooded rice paddies in Zimbabwe. The objective of this study was to quantify greenhouse gas emissions from dambo rice under different tillage treatments, which were conventional tillage, no tillage, tied ridges, tied fallows, and mulching. Average soil nitrous oxide emissions were 5.9, 0.2, 5.4, 5.2 and 7.8 μg·m-2·hr-1 for tied fallows, conventional tillage, tied ridges, mulching and no tillage respectively. Average methane emission was 0.35 mg·m-2·hr-1 and maximum as 1.62 mg·m-2·hr-1. Average methane emissions for the different tillage systems were 0.20, 0.18, 0.45, 0.52 and 0.38 mg·m-2·hr-1 for tied fallows, conventional tillage, tied ridges, mulching and no tillage respectively. Carbon dioxide emissions were 98.1, 56.0, 69.9, 94.8 and 95.5 mg·m-2·hr-1 for tied fallows, conventional tillage, tied ridges, mulching and no tillage respectively. The estimated emissions per 150 day cropping season were 1.4, 3.6 and 0.6 kg·ha-1 for methane, carbon dioxide and nitrous oxide respectively. We concluded that intermittently saturated dambo rice Paddys are a potential source of greenhouse gases which is important to global greenhouse gas budgets, thus, they deserve more careful study.

Participatory diagnosis and prioritization of constraints to cattle production in some smallholder farming areas of Zimbabwe

A participatory epidemiological study was conducted to identify and prioritize constraints to livestock health and production on smallholder farms in Sanyati and Gokwe districts of Zimbabwe. Questionnaires were administered to 294 randomly selected livestock owners across the two districts. Livestock diseases (29% of the respondents), high cost of drugs (18.21%), weak veterinary extension (15.18%), inadequate grazing (13.60%), inadequate water (13.54%), and livestock thefts (10.44%) were the major livestock health and production constraints identified. The number of diseases reported varied (P<0.05) with livestock species and nature of causative agent. Out of the 36 diseases mentioned by farmers, 50%, 22.2%, 19.4%, 5.5% and 2.8% were diseases of cattle, sheep and goats, domestic chicken, donkeys, and guinea fowls, respectively. Seven (19.4%) of the 36 diseases including rabies and foot and mouth disease were those listed by the OIE. Thirty-four percent of the respondents rated bovine dermatophilosis as the most important livestock disease. Respondents rated, in descending order, other diseases including tick borne diseases (21%); a previously unreported disease, “Magwiriri” or “Ganda renzou” in vernacular (14%); mastitis (11%); parafilariosis (11%); and blackleg (9%). Cattle skin samples from “Magwiriri” cases had Besnoitia besnoiti parasites. Overall, this study revealed factors and diseases that limit livestock production in Zimbabwe and are of global concern; in addition, the study showed that the skin diseases, bovine dermatophilosis and besnoitiosis, have recently emerged and appear to be spreading, likely a consequence of ectoparasite control demise in smallholder farming areas of Zimbabwe over the last 15 years.

Seasonal changes in body condition scores of pigs and chemical composition of pig feed resources in a semi- arid smallholder farming area of Zimbabwe

There are few studies quantifying the productivity of rural pigs and evaluating the nutritive value of non-conventional feeds, such as weeds. The objectives of this study were to determine changes in body condition scores of boars and lactating sows and investigate changes in the chemical composition of commonly used pig feed resources in a smallholder farming area of Zimbabwe. Body condition scores (BCS) were measured monthly between October and April. Commelina benghalensis (wandering jew) and Richardia brasiliensis (Mexican clover) were collected monthly, between October and March, for proximate and amino acid analysis. Sows had lower BCS than boars (P<0.05). The Neutral detergent fibre (NDF) and acid detergent fibre (ADF) contents of C. benghalensis were lower (P<0.05) than those of R. brasiliensis. C. benghalensis had about twice the amount of crude protein (CP) compared to R. brasiliensis. Lysine, methionine and cysteine, which are the most important amino acids in pig nutrition, were similar in groundnut hulls and R. brasiliensis. C. benghalensis had higher (P<0.05) levels of threonine, tryptophan, isoleucine, leucine, histidine, phenylalanine, tyrosine, valine, arginine, serine, aspartic acid, glutamic acid, glycine and alanine than R. brasiliensis. The proportion of essential amino acids (EAA) was significantly higher (P<0.05) in R. brasiliensis. A further study to determine the digestibility and growth performance of pigs fed on these non-conventional diets is needed. Key words: Rural pig production, body condition scoring, Commelina benghalensis,proximate analysis, Richardia brasiliensis.

Fertilizer use efficiency and nitrate leaching in a tropical sandy soil.

Maize (Zea mays L.) production in the smallholder farming areas of Zimbabwe is based on both organic and mineral nutrient sources. A study was conducted to determine the effect of composted cattle manure, mineral N fertilizer, and their combinations on NO3 concentrations in leachate leaving the root zone and to establish N fertilization rates that minimize leaching. Maize was grown for three seasons (1996-1997, 1997-1998, and 1998-1999) in field lysimeters repacked with a coarse-grained sandy soil (Typic Kandiustalf). Leachate volumes ranged from 480 to 509 mm yr(-1) (1395 mm rainfall) in 1996-1997, 296 to 335 mm yr(-1) (840 mm rainfall) in 1997-1998, and 606 to 635 mm yr(-1) (1387 mm rainfall) in 1998-1999. Mineral N fertilizer, especially the high rate (120 kg N ha(-1)), and manure plus mineral N fertilizer combinations resulted in high NO3 leachate concentrations (up to 34 mg N L(-1)) and NO3 losses (up to 56 kg N ha(-1) yr(-1)) in 1996-1997, which represent both environmental and economic concerns. Although the leaching losses were relatively small in the other seasons, they are still of great significance in African smallholder farming where fertilizer is unaffordable for most farmers. Nitrate leaching from sole manure treatments was relatively low (average of less than 20 kg N ha(-1) yr(-1)), whereas the crop uptake efficiency of mineral N fertilizer was enhanced by up to 26% when manure and mineral N fertilizer were applied in combination. The low manure (12.5 Mg ha(-1)) plus 60 kg N ha(-1) fertilizer treatment was best in terms of maintaining dry matter yield and minimizing N leaching losses.

Fertilizer Use Efficiency and Nitrate Leaching in a Tropical Sandy Soil

Maize (Zea mays L.) production in the smallholder farming areas of Zimbabwe is based on both organic and mineral nutrient sources. A study was conducted to determine the effect of composted cattle manure, mineral N fertilizer, and their combinations on NO3 concentrations in leachate leaving the root zone and to establish N fertilization rates that minimize leaching. Maize was grown for three seasons (1996–1997, 1997–1998, and 1998–1999) in field lysimeters repacked with a coarse-grained sandy soil (Typic Kandiustalf). Leachate volumes ranged from 480 to 509 mm yr−1 (1395 mm rainfall) in 1996–1997, 296 to 335 mm yr−1 (840 mm rainfall) in 1997–1998, and 606 to 635 mm yr−1 (1387 mm rainfall) in 1998–1999. Mineral N fertilizer, especially the high rate (120 kg N ha−1), and manure plus mineral N fertilizer combinations resulted in high NO3 leachate concentrations (up to 34 mg N L−1) and NO3 losses (up to 56 kg N ha−1 yr−1) in 1996–1997, which represent both environmental and economic concerns. Although the leaching losses were relatively small in the other seasons, they are still of great significance in African smallholder farming where fertilizer is unaffordable for most farmers. Nitrate leaching from sole manure treatments was relatively low (average of less than 20 kg N ha−1 yr−1), whereas the crop uptake efficiency of mineral N fertilizer was enhanced by up to 26% when manure and mineral N fertilizer were applied in combination. The low manure (12.5 Mg ha−1) plus 60 kg N ha−1 fertilizer treatment was best in terms of maintaining dry matter yield and minimizing N leaching losses.

The use of faecal progestin measurements to monitor reproductive activity in Mashona cows in a smallholder farming area of Zimbabwe.

The objectives of this study were to investigate the relationship between the concentrations of progesterone (P4) in the peripheral circulation and progestins in the faeces of cows in a smallholder farming area and to monitor the ovarian activity of such cows. The study was carried out in Sanyati smallholder farming area, located 250 km southwest of Harare. Blood and faecal samples for P4 and progestin determination, respectively, were obtained once a week from 35 Mashona type cows that belonged to farmers from three different villages. The cows were weighed once every month and all births were recorded. The concentrations of progestins in faeces and P4 in plasma were positively correlated (r = 0.72, p < 0.01). Most of the non-pregnant cows (65%) cycled during the rainy season. Most of those that were acyclic at this time were undergoing post-partum anoestrus. During the dry season, most cows (58%) became acyclic as forage became scarce and of poor quality. Thirty-two calves were born during the study period, mostly during the first or last two months of the year, when there was enough forage. The mean calving to first oestrus in 14 cows that recalved was 71 +/- 49 days. Eight of these 14 cows conceived again, the calving to conception interval being 173 +/- 94 days. The cows' liveweights were highest in April, at the end of the rainy season. By the end of the dry season, the cows had lost, on average, 15% of their peak weight.

The effect of tick control on bovine dermatophilosis in a smallholder farming area of Zimbabwe

Three different methods of acaricide (Amitraz) application were tested on cattle in Sanyati smallholder farming area to determine the effectiveness of control of ticks on the prevalence of clinical dermatophilosis during a twelve-month period. The acaricide application methods were plunge dipping, hand spraying and a combination of the two. Throughout the twelve months, the cattle plunge dipped had a higher number of ticks (p < 0.05) compared to those using the other two methods. Amblyomma variegatum ticks accounted for 53% of the overall number of ticks counted on cattle. In addition, the occurrence of dermatophilosis was higher (p < 0.05) in cattle plunge dipped and hand sprayed in combination with plunge dipping compared to those hand sprayed only. These results indicate that hand spraying of acaricide might be the method of choice to reduce both tick infestations and the occurrence of dermatophilosis in smallholder cattle herds.

Decomposition and nutrient release from mango and miombo woodland litter in Zimbabwe

Litter inputs from trees are potentially important in agroforestry systems as sources of nutrients and organic matter. In the smallholder farming areas of Zimbabwe, litter from trees in natural woodlands (miombo) is applied to croplands as a soil amendment. Soils in smallholder areas are generally sandy and contain low amounts of C, N, P and S. Mango trees are planted widely on smallholder farms, but miombo litter is a preferred soil amendment to mango litter. Leaf litter from mango ( Mangifera indica L.) and miombo woodland were assessed as soil amendments through decomposition and nutrient release studies in Zimbabwe. Mass loss was assessed in 7 mm mesh litter bags. Changes in lignin, cellulose, hemicellulose, polyphenols and nutrient release were also assessed. Miombo litter had higher initial concentrations of N, P, S, Mg and lignin, and lower polyphenol contents than mango litter. Mass loss was faster in miombo than mango litter, with miombo litter losing 72% of the initial mass over 18 months in comparison with a 55% mass loss for mango litter under the same conditions. Initial litter N, lignin content, and Lignin–N ratios were correlated strongly with mass loss. The rate of lignin loss was higher in miombo than in mango litter. Total polyphenols could not be detected in either litter type after 2 months. There was less N immobilization in miombo litter than in mango during the 18-month study. Net N mobilization in miombo litter accounted for 66% of the initial nitrogen. N immobilization and release correlated strongly with initial litter N, lignin content and Lignin–N. Miombo litter also released more P and S than mango litter over 18 months. More rapid nutrient release by miombo litter may be the reason for its being a preferred soil amendment to mango litter, but mango litter could be used to maintain or enhance soil C.