Rebecca Zengeni - Academia.edu (original) (raw)

Papers by Rebecca Zengeni

Agriculture

No-till (NT) has been said to conserve soil moisture, maintain or increase organic matter (OM), a... more No-till (NT) has been said to conserve soil moisture, maintain or increase organic matter (OM), and improve crop production compared to conventional tillage (CT). However, very few studies have explored the effect of these under dry-land agriculture with occasional tillage where ploughing is performed only after several years of NT, especially in KwaZulu–Natal. The aim of this study was to assess the effect of tillage and fertilizer application on selected physicochemical soil properties under rain-fed maize production. Soil samples from NT, conventional tillage in the 5th season (CT-Y5), and annual conventional tillage (CT-A) with 0, 60, 120, 240 kg N ha−1 were taken at 0–10, 10–20, and 20–30 cm and analysed for pH, EC, exchangeable acidity, exchangeable bases, C:N, gravimetric water content, bulk density, and soil texture. Results showed that NT at 0 and 60 kg N ha−1 in 0–10 cm had higher bases, gravimetric water content, pH, and EC compared CT-Y5 and CT-A (p < 0.05). At 10–20 ...

Agronomy

Processes governing soil organic matter (SOM) decomposition and mineralization are important for ... more Processes governing soil organic matter (SOM) decomposition and mineralization are important for soil fertility and ecosystem sustainability. However, in the sub-Saharan region, limited work has been conducted on SOM dynamics; therefore, there was an imperative need for this study. The objective of this study was to determine the phosphorus (P) and nitrogen (N) dynamics in soil under different tillage and fertilizer management practices. The field trial was arranged as a randomized split plot design, with tillage forming the whole plot and the fertilizer application rate being the sub-plot. The tillage techniques were no-till (NT), annual tillage (CT-ANNUAL) and conventional tillage every fifth season (CT-Y5), whereby NT was practiced for four consecutive seasons, and in the fifth season, conventional tillage was employed. For all these tillage techniques, urea fertilizer was applied in amounts of 60, 120 and 240 kg N ha−1 with a control for each tillage treatment. Ammonium and nitr...

Agronomy

Conservation tillage has been considered a smart agriculture practice which preserves soil organi... more Conservation tillage has been considered a smart agriculture practice which preserves soil organic carbon (SOC). However, little work on the labile C fractions in South Africa has been documented. As such, this work focused on C fractions under different management systems. The objective of this study was to assess the impact of different tillage techniques and fertilizer application rates on soil C fractions along the soil profile. Samples from no-till (NT), conventional tillage after 5th season (CT-Y5), and annual conventional tillage, longer than 5 years (CT-ANNUAL) at 0, 60, 120, and 240 kg N ha−1 were taken at 0–10, 10–20, and 20–30 cm depths and analyzed for C fractions. The 30 cm depth was chosen as the sampling depth because of the 30 cm plough layer. At 0–10 cm, soil NT had higher total C, organic C, particulate organic C (POC), and permanganate oxidizable C (POxC) for all application rates, especially in the control treatment, compared to both the CT-Y5 and CT-ANNUAL treat...

Agronomy

Genetic diversity is invaluable in developing climate-smart and drought-adapted wheat varieties. ... more Genetic diversity is invaluable in developing climate-smart and drought-adapted wheat varieties. The aim of this study was to determine the extent of genetic variation present in wheat germplasm collections for biomass allocation and drought tolerance based on complementary phenotypic and root attributes and high-density single nucleotide polymorphism (SNP) markers to select breeding parents. A total of 97 bread wheat (Triticum aestivum L.) genotypes were evaluated in field and greenhouse trials under drought-stressed and non-stressed conditions. The molecular variance analysis showed that the intrapopulation variance was very high at 99%, with a small minimal inter-population variance (1%). The genetic distance, polymorphic information content and expected heterozygosity were 0.20–0.88, 0.24–1.00 and 0.29–0.58, respectively. The cluster analysis based on SNP data showed that 44% and 28% of the assessed genotypes maintained their genetic groups when compared to hierarchical clusters...

April 2021, 2021

Breeding for drought tolerance in plants is challenging because it is controlled by multiple gene... more Breeding for drought tolerance in plants is challenging because it is controlled by multiple genes. Grain yield, the trait of primary interest in maize, is characterized by low heritability, high genotype by environment interaction, and low variation under drought conditions, which further complicates selection. To circumvent these challenges, secondary traits that are highly correlated with grain yield are indirectly selected under drought conditions. Although considerable success in terms of yield gains under drought stress has been reported in both temperate and tropical maize breeding programmes, climate change exacerbated droughts coupled with high population growth necessitates continuous improvement of maize varieties. Understanding the genetics of associated secondary traits is essential in elucidating drought tolerance. The identification of quantitative trait loci (QTL) and candidate genes conferring drought tolerance and the subsequent development of relevant molecular ma...

Nelson Mandela Metropolitan University, 2013

Food Security for African Smallholder Farmers, 2022

Journal of Agriculture and Rural Development in the Tropics and Subtropics, 2018

The diversity of smallholder farms in space, resource endowment, production and consumption decis... more The diversity of smallholder farms in space, resource endowment, production and consumption decisions are often a hindrance to the design, targeting, implementation and scaling out of agricultural development projects. Understanding farm heterogeneity is crucial in targeting interventions that can potentially contribute to improved crop productivity, food security and livelihood sustainability. The study sought to define and understand farm typology in a resettlement smallholder food-cash crop production area in Zimbabwe. Data was collected from five focus group discussions (FGDs), and 102 household interviews. Principal component analysis (PCA), multiple correspondence analysis (MCA) and cluster analysis were used to analyse quantitative and qualitative data variables and aggregate farms into clusters according to production means, socio-economics and demographics. The three identified farm types were (i) resource-endowed, commercial oriented farms, (ii) medium resourced and (iii) ...

SSRN Electronic Journal, 2021

Journal of Soil Science and Plant Nutrition, 2021

South African Journal of Science, 2020

The inadequacy of the nutrient supply of most tropical and sub-tropical soils may be curbed throu... more The inadequacy of the nutrient supply of most tropical and sub-tropical soils may be curbed through organic material recycling, thus reducing the need for mineral fertiliser use. To promote tobacco waste recycling in a smallholder food-cash crop production system, nutrient uptake, dry biomass yield and taste of oilseed rape (Brassica napus L.) and soil chemical properties were determined on a sandy loam soil under field conditions. The experiment was a randomised complete block design with three blocks and eight treatments, namely, control (no amendment), mineral fertiliser (121, 30.8, 24.6 kg/ha N, P and K, respectively), uncomposted tobacco leaf scrap (TSC) and compost of TSC and cattle manure (TSC-CM) at 5, 20 and 40 t/ha. N, P and K uptake and dry biomass yield of oilseed rape were higher (p<0.05) than control with 40 t/ha TSC-CM and mineral fertiliser application at 3 weeks after transplanting (WAT), while significant improvements with TSC were observed from 5 WAT. Mineral N...

Acta Agriculturae Scandinavica, Section B — Soil & Plant Science, 2020

The success of a breeding programme can be determined by the level of genetic diversity that exis... more The success of a breeding programme can be determined by the level of genetic diversity that exists among breeding materials. This study was carried out to (i) determine the level of genetic diversity that exist among the collection of tropical provitamin A maize inbred lines and (ii) evaluate the genetic structure and divergence of provitamin A maize inbred lines. Forty-six advanced provitamin A inbred lines obtained from the International Maize and Wheat Improvement Centre (CIMMYT) and International Institute of Tropical Agriculture (IITA) were genotyped using 3047 single nucleotide polymorphism (SNP) markers. Genotyping was done following an Illumina Infinium HD Assay Ultra protocol. Eight six percent of the SNPs were polymorphic with the mean polymorphic information content of 0.36. Cluster analysis displayed two distinct clusters. The average pairwise genetic distance among the inbred lines was 0.60. The average gene diversity was 0.359. Variation was partitioned into among individuals (78%), among populations (12%) and within individuals (10%). Overall results suggest the inbred lines are genetically diverse. The key implication of this study is that selection should be done from genetically diverse inbred lines in order to exploit heterosis when developing hybrids.

Agricultural Water Management, 2020

Water is a limiting natural resource for agricultural production. While it is well accepted that ... more Water is a limiting natural resource for agricultural production. While it is well accepted that crop types differ in their water use efficiency (WUE), there is no consensus on the main factors affecting WUE of main field crops, which was the motivation of the current study. The effects of rainfall pattern, soil type and climatic regime on crop WUE were evaluated using data from 514 experiments around the world published in ISI journal papers. The results confirmed that crop type had a significant effect (p < 0.05) on WUE with cereals producing on average 2.37 kg of dry grain per cubic meter (m −3) of water followed by oilseeds (0.69 kg m −3), fibre crops (0.45 kg m −3) and legumes (0.42 kg m −3). Amongst cereals, maize (3.78 kg m −3) and sorghum (2.52 kg m −3) were more water-use efficient than wheat (1.02 kg m −3), barley (1.21 kg m −3) and millet (0.47 kg m −3). Overall, maize was the most water use efficient crop under well-watered conditions (9.90 kg m −3), but sorghum was the most efficient under dry conditions (5.99 kg m −3). WUE of crops increased from desert to tropical through subtropical climate. Moreover, WUE tended to correlate positively with soil organic carbon content (r = 0.86) and negatively with clay content (r=−0.78) and soil bulk density (r=−0.85). These results provide information that is important for making decisions on crop selection in a context of increased climate variability and for crop variety development with enhanced WUE. However, there is need for more research to gain more understanding of the mechanisms responsible for the observed trends and causes of the unexplained variability.

Agronomy, 2019

Provitamin A maize (Zea mays L.) biofortification is an ideal complementary means of combating vi... more Provitamin A maize (Zea mays L.) biofortification is an ideal complementary means of combating vitamin A deficiency (VAD) in sub-Saharan Africa where maize consumption is high coupled by high VAD incidences. However, drought remains a major abiotic constraint to maize productivity in this region. Comprehensive drought screening of initial breeding materials before advancing them is important to achieve genetic gain. In this study, 46 provitamin-A inbred lines were screened for drought tolerance in the greenhouse and field under drought and optimum conditions using β-carotene content (BCC), grain yield (GY), and selected morphophysiological and biochemical traits. The results revealed that BCC, morphophysiological and biochemical traits were effective in discriminating among genotypes. Number of ears per plant (EPP), stomatal conductance (Gs), delayed leaf senescence (SEN), leaf rolling (RL), chlorophyll content (CC) and free proline content (PC) proved to be ideal traits to use when...

International Journal of Recycling of Organic Waste in Agriculture, 2019

Purpose Recovery of nutrients from water using duckweed and their reuse has significance in closi... more Purpose Recovery of nutrients from water using duckweed and their reuse has significance in closing the loop on nutrient transfer from anthropogenic sources. This study investigated the effect of rate of application and pre-incubation period of duckweed on biomass and nutrient uptake of Swiss chard (Fordhook giant). Methods Two glasshouse experiments were laid out in randomized complete block designs with three replicates. In the first experiment, Swiss chard was grown on two soils (ferralsol and regosol) amended with Wolffia arrhiza biomass at 0, 50, 100 and 200% of the recommended nitrogen rate. In the second experiment, the same vegetable was grown on the ferralsol amended with W. arrhiza and Lemna minor at recommended nitrogen rate, with pre-incubation periods of 0, 14 and 28 days. Results Application of W. arrhiza biomass increased Swiss chard dry matter by 23-45% compared to the negative control. The positive control (urea at 100 kg N ha −1 rate) had highest Swiss chard biomass. Higher rates than 100 kg N ha −1 had no added benefit on dry matter accumulation and nitrogen uptake of Swiss chard. Pre-incubation of duckweed for 28 days improved nutrient uptake, resulting in higher dry matter than shorter periods. The Swiss chard dry matter after pre-incubation for 28 days was similar to that from urea application. Conclusion Findings from this study suggest that duckweed is a resource with beneficial use for nutrient supply to vegetables, especially when appropriate rates are used with pre-incubation.

South African Journal of Plant and Soil, 2018

Effects of long-term application of pig slurry (PS) on soil organic carbon (SOC) pools, nutrients... more Effects of long-term application of pig slurry (PS) on soil organic carbon (SOC) pools, nutrients and maize tissue composition under continuous conventional tillage in a maize-soyabean rotation system in subhumid subtropical environments are unclear. The soil and plant parameters have important implications for PS management under intensive agriculture. Soil (0-20 cm depth) and maize tissue were sampled from lands treated with PS for 0, 10 and 20 years and analysed for soil chemical properties and plant nutrients. Soil available phosphorus, potassium, copper and zinc and tissue concentrations increased due to PS application. Total nitrogen and SOC declined, whereas soil microbial biomass carbon (MBC), hot-water-soluble carbon (HWSC) and microbial quotient (MB/SOC) increased with PS application period. The SOC was negatively correlated to MBC and HWSC (r = −0.472 and −0.663, respectively). Increase in MBC, MBC/SOC and HWSC indicated presence of an untenable soil organic matter with limited possibility of carbon sequestration. The findings imply that long-term PS application, with conventional tillage, not only increased most plant nutrients but also vulnerability of SOC.

Land Degradation & Development, 2019

Most of rural South Africa is semi arid, experiencing a variable climate with extreme weather eve... more Most of rural South Africa is semi arid, experiencing a variable climate with extreme weather events such as droughts and floods. Communal farmers experience problems of getting reliable weather information. Datasets used to describe climate change and variability rely on spatially interpolated gridded data from a few weather stations. The ability of gridded climate data to describe climate variability at the local level has been widely questioned. Communal farmers have developed indigenous strategies to cope with these extremes in order to sustain agricultural production. The objective of this study was to document indigenous strategies that smallholder farmers in Bergville and Msinga, in KwaZulu Natal Province, use to predict weather, conserve soil and water, and manage climate extremes events. Data were gathered through key informant interviews, focus group discussions, and questionnaire. Results showed that more farmers in Msinga than Bergville observed reduced rainfalls and increased temperatures as an indicator of climate variability (p<.05). Bergville and Msinga communal farmers use indigenous indicators such as wind and cloud patterns, animal and bird behaviour, moon shape, and position of the sun to predict weather. Communal farmers using manure were 0.17 times more likely to conserve soil and water when compared with those using artificial fertilizer (p<.05). Thus, indigenous knowledge system (IKS) can be used to conserve soil and water and manage climate extremes and variability. Communal farmers also resist adopting unfamiliar strategies that are forced on them without proper engagement. Communal farmers have managed to survive extreme weather events using IKS.

Journal of Agronomy and Crop Science, 2019

The biomass allocation pattern of plants to shoots and roots is a key in the cycle of elements su... more The biomass allocation pattern of plants to shoots and roots is a key in the cycle of elements such as carbon, water and nutrients with, for instance, the greatest allocations to roots fostering the transfer of atmospheric carbon to soils through photosynthesis. Several studies have investigated the root to shoot ratio (R:S) biomass of existing crops but variation within a crop species constitutes an important information gap for selecting genotypes aiming for increasing soil carbon stocks for climate change mitigation and food security. The objectives of this study were to evaluate agronomic performance and quantify biomass production and allocation between roots and shoots, in response to different soil water levels to select promising genotypes for breeding. Field and greenhouse experiments were carried out using 100 genotypes including wheat and Triticale under drought-stressed and non-stressed conditions. The experiments were setup using a 10 × 10 alpha lattice design with two replications under water stress and non-stress conditions. The following phenotypic traits were collected: number of days to heading (DTH), number of productive tillers per plant (NPT), plant height (PH), days to maturity (DTM), spike length (SL), kernels per spike (KPS), thousand kernel weight (TKW), root biomass (RB), shoot biomass (SB), root to shoot ratio (R:S) and grain yield (GY).

Water Environment Research, 2018

Studies focusing on manipulation of growth conditions for duckweed Wolffia arrhiza to promote bio... more Studies focusing on manipulation of growth conditions for duckweed Wolffia arrhiza to promote biomass for crop nutrient supply, are scarce. The effects of swine lagoon water (SLW) concentration and its replenishment and harvest regimes on selected properties of W. arrhiza were investigated. Dry matter and average growth rate of W. arrhiza were not affected by SLW replenishment periods, whereas the properties decreased with increasing concentration of SLW. The carbon and carbon/nitrogen content increased as the period between solution replenishment increased and as SLW concentration declined from 15 to 5%. Harvesting regimes did not affect the nitrogen content and uptake of duckweed, NH þ 4-N, and mineral-N of SLW. Harvesting duckweed once per week resulted in higher growth rate and biomass, compared with twice a week. Findings from this study suggest that W. arrhiza cultured on 10% SLW and harvested once a week yields biomass with nitrogen content suitable for crop nutrient supply. Water Environ. Res., 90, 2066 (2018).

Agriculture

No-till (NT) has been said to conserve soil moisture, maintain or increase organic matter (OM), a... more No-till (NT) has been said to conserve soil moisture, maintain or increase organic matter (OM), and improve crop production compared to conventional tillage (CT). However, very few studies have explored the effect of these under dry-land agriculture with occasional tillage where ploughing is performed only after several years of NT, especially in KwaZulu–Natal. The aim of this study was to assess the effect of tillage and fertilizer application on selected physicochemical soil properties under rain-fed maize production. Soil samples from NT, conventional tillage in the 5th season (CT-Y5), and annual conventional tillage (CT-A) with 0, 60, 120, 240 kg N ha−1 were taken at 0–10, 10–20, and 20–30 cm and analysed for pH, EC, exchangeable acidity, exchangeable bases, C:N, gravimetric water content, bulk density, and soil texture. Results showed that NT at 0 and 60 kg N ha−1 in 0–10 cm had higher bases, gravimetric water content, pH, and EC compared CT-Y5 and CT-A (p < 0.05). At 10–20 ...

Agronomy

Processes governing soil organic matter (SOM) decomposition and mineralization are important for ... more Processes governing soil organic matter (SOM) decomposition and mineralization are important for soil fertility and ecosystem sustainability. However, in the sub-Saharan region, limited work has been conducted on SOM dynamics; therefore, there was an imperative need for this study. The objective of this study was to determine the phosphorus (P) and nitrogen (N) dynamics in soil under different tillage and fertilizer management practices. The field trial was arranged as a randomized split plot design, with tillage forming the whole plot and the fertilizer application rate being the sub-plot. The tillage techniques were no-till (NT), annual tillage (CT-ANNUAL) and conventional tillage every fifth season (CT-Y5), whereby NT was practiced for four consecutive seasons, and in the fifth season, conventional tillage was employed. For all these tillage techniques, urea fertilizer was applied in amounts of 60, 120 and 240 kg N ha−1 with a control for each tillage treatment. Ammonium and nitr...

Agronomy

Conservation tillage has been considered a smart agriculture practice which preserves soil organi... more Conservation tillage has been considered a smart agriculture practice which preserves soil organic carbon (SOC). However, little work on the labile C fractions in South Africa has been documented. As such, this work focused on C fractions under different management systems. The objective of this study was to assess the impact of different tillage techniques and fertilizer application rates on soil C fractions along the soil profile. Samples from no-till (NT), conventional tillage after 5th season (CT-Y5), and annual conventional tillage, longer than 5 years (CT-ANNUAL) at 0, 60, 120, and 240 kg N ha−1 were taken at 0–10, 10–20, and 20–30 cm depths and analyzed for C fractions. The 30 cm depth was chosen as the sampling depth because of the 30 cm plough layer. At 0–10 cm, soil NT had higher total C, organic C, particulate organic C (POC), and permanganate oxidizable C (POxC) for all application rates, especially in the control treatment, compared to both the CT-Y5 and CT-ANNUAL treat...

Agronomy

Genetic diversity is invaluable in developing climate-smart and drought-adapted wheat varieties. ... more Genetic diversity is invaluable in developing climate-smart and drought-adapted wheat varieties. The aim of this study was to determine the extent of genetic variation present in wheat germplasm collections for biomass allocation and drought tolerance based on complementary phenotypic and root attributes and high-density single nucleotide polymorphism (SNP) markers to select breeding parents. A total of 97 bread wheat (Triticum aestivum L.) genotypes were evaluated in field and greenhouse trials under drought-stressed and non-stressed conditions. The molecular variance analysis showed that the intrapopulation variance was very high at 99%, with a small minimal inter-population variance (1%). The genetic distance, polymorphic information content and expected heterozygosity were 0.20–0.88, 0.24–1.00 and 0.29–0.58, respectively. The cluster analysis based on SNP data showed that 44% and 28% of the assessed genotypes maintained their genetic groups when compared to hierarchical clusters...

April 2021, 2021

Breeding for drought tolerance in plants is challenging because it is controlled by multiple gene... more Breeding for drought tolerance in plants is challenging because it is controlled by multiple genes. Grain yield, the trait of primary interest in maize, is characterized by low heritability, high genotype by environment interaction, and low variation under drought conditions, which further complicates selection. To circumvent these challenges, secondary traits that are highly correlated with grain yield are indirectly selected under drought conditions. Although considerable success in terms of yield gains under drought stress has been reported in both temperate and tropical maize breeding programmes, climate change exacerbated droughts coupled with high population growth necessitates continuous improvement of maize varieties. Understanding the genetics of associated secondary traits is essential in elucidating drought tolerance. The identification of quantitative trait loci (QTL) and candidate genes conferring drought tolerance and the subsequent development of relevant molecular ma...

Nelson Mandela Metropolitan University, 2013

Food Security for African Smallholder Farmers, 2022

Journal of Agriculture and Rural Development in the Tropics and Subtropics, 2018

The diversity of smallholder farms in space, resource endowment, production and consumption decis... more The diversity of smallholder farms in space, resource endowment, production and consumption decisions are often a hindrance to the design, targeting, implementation and scaling out of agricultural development projects. Understanding farm heterogeneity is crucial in targeting interventions that can potentially contribute to improved crop productivity, food security and livelihood sustainability. The study sought to define and understand farm typology in a resettlement smallholder food-cash crop production area in Zimbabwe. Data was collected from five focus group discussions (FGDs), and 102 household interviews. Principal component analysis (PCA), multiple correspondence analysis (MCA) and cluster analysis were used to analyse quantitative and qualitative data variables and aggregate farms into clusters according to production means, socio-economics and demographics. The three identified farm types were (i) resource-endowed, commercial oriented farms, (ii) medium resourced and (iii) ...

SSRN Electronic Journal, 2021

Journal of Soil Science and Plant Nutrition, 2021

South African Journal of Science, 2020

The inadequacy of the nutrient supply of most tropical and sub-tropical soils may be curbed throu... more The inadequacy of the nutrient supply of most tropical and sub-tropical soils may be curbed through organic material recycling, thus reducing the need for mineral fertiliser use. To promote tobacco waste recycling in a smallholder food-cash crop production system, nutrient uptake, dry biomass yield and taste of oilseed rape (Brassica napus L.) and soil chemical properties were determined on a sandy loam soil under field conditions. The experiment was a randomised complete block design with three blocks and eight treatments, namely, control (no amendment), mineral fertiliser (121, 30.8, 24.6 kg/ha N, P and K, respectively), uncomposted tobacco leaf scrap (TSC) and compost of TSC and cattle manure (TSC-CM) at 5, 20 and 40 t/ha. N, P and K uptake and dry biomass yield of oilseed rape were higher (p<0.05) than control with 40 t/ha TSC-CM and mineral fertiliser application at 3 weeks after transplanting (WAT), while significant improvements with TSC were observed from 5 WAT. Mineral N...

Acta Agriculturae Scandinavica, Section B — Soil & Plant Science, 2020

The success of a breeding programme can be determined by the level of genetic diversity that exis... more The success of a breeding programme can be determined by the level of genetic diversity that exists among breeding materials. This study was carried out to (i) determine the level of genetic diversity that exist among the collection of tropical provitamin A maize inbred lines and (ii) evaluate the genetic structure and divergence of provitamin A maize inbred lines. Forty-six advanced provitamin A inbred lines obtained from the International Maize and Wheat Improvement Centre (CIMMYT) and International Institute of Tropical Agriculture (IITA) were genotyped using 3047 single nucleotide polymorphism (SNP) markers. Genotyping was done following an Illumina Infinium HD Assay Ultra protocol. Eight six percent of the SNPs were polymorphic with the mean polymorphic information content of 0.36. Cluster analysis displayed two distinct clusters. The average pairwise genetic distance among the inbred lines was 0.60. The average gene diversity was 0.359. Variation was partitioned into among individuals (78%), among populations (12%) and within individuals (10%). Overall results suggest the inbred lines are genetically diverse. The key implication of this study is that selection should be done from genetically diverse inbred lines in order to exploit heterosis when developing hybrids.

Agricultural Water Management, 2020

Water is a limiting natural resource for agricultural production. While it is well accepted that ... more Water is a limiting natural resource for agricultural production. While it is well accepted that crop types differ in their water use efficiency (WUE), there is no consensus on the main factors affecting WUE of main field crops, which was the motivation of the current study. The effects of rainfall pattern, soil type and climatic regime on crop WUE were evaluated using data from 514 experiments around the world published in ISI journal papers. The results confirmed that crop type had a significant effect (p < 0.05) on WUE with cereals producing on average 2.37 kg of dry grain per cubic meter (m −3) of water followed by oilseeds (0.69 kg m −3), fibre crops (0.45 kg m −3) and legumes (0.42 kg m −3). Amongst cereals, maize (3.78 kg m −3) and sorghum (2.52 kg m −3) were more water-use efficient than wheat (1.02 kg m −3), barley (1.21 kg m −3) and millet (0.47 kg m −3). Overall, maize was the most water use efficient crop under well-watered conditions (9.90 kg m −3), but sorghum was the most efficient under dry conditions (5.99 kg m −3). WUE of crops increased from desert to tropical through subtropical climate. Moreover, WUE tended to correlate positively with soil organic carbon content (r = 0.86) and negatively with clay content (r=−0.78) and soil bulk density (r=−0.85). These results provide information that is important for making decisions on crop selection in a context of increased climate variability and for crop variety development with enhanced WUE. However, there is need for more research to gain more understanding of the mechanisms responsible for the observed trends and causes of the unexplained variability.

Agronomy, 2019

Provitamin A maize (Zea mays L.) biofortification is an ideal complementary means of combating vi... more Provitamin A maize (Zea mays L.) biofortification is an ideal complementary means of combating vitamin A deficiency (VAD) in sub-Saharan Africa where maize consumption is high coupled by high VAD incidences. However, drought remains a major abiotic constraint to maize productivity in this region. Comprehensive drought screening of initial breeding materials before advancing them is important to achieve genetic gain. In this study, 46 provitamin-A inbred lines were screened for drought tolerance in the greenhouse and field under drought and optimum conditions using β-carotene content (BCC), grain yield (GY), and selected morphophysiological and biochemical traits. The results revealed that BCC, morphophysiological and biochemical traits were effective in discriminating among genotypes. Number of ears per plant (EPP), stomatal conductance (Gs), delayed leaf senescence (SEN), leaf rolling (RL), chlorophyll content (CC) and free proline content (PC) proved to be ideal traits to use when...

International Journal of Recycling of Organic Waste in Agriculture, 2019

Purpose Recovery of nutrients from water using duckweed and their reuse has significance in closi... more Purpose Recovery of nutrients from water using duckweed and their reuse has significance in closing the loop on nutrient transfer from anthropogenic sources. This study investigated the effect of rate of application and pre-incubation period of duckweed on biomass and nutrient uptake of Swiss chard (Fordhook giant). Methods Two glasshouse experiments were laid out in randomized complete block designs with three replicates. In the first experiment, Swiss chard was grown on two soils (ferralsol and regosol) amended with Wolffia arrhiza biomass at 0, 50, 100 and 200% of the recommended nitrogen rate. In the second experiment, the same vegetable was grown on the ferralsol amended with W. arrhiza and Lemna minor at recommended nitrogen rate, with pre-incubation periods of 0, 14 and 28 days. Results Application of W. arrhiza biomass increased Swiss chard dry matter by 23-45% compared to the negative control. The positive control (urea at 100 kg N ha −1 rate) had highest Swiss chard biomass. Higher rates than 100 kg N ha −1 had no added benefit on dry matter accumulation and nitrogen uptake of Swiss chard. Pre-incubation of duckweed for 28 days improved nutrient uptake, resulting in higher dry matter than shorter periods. The Swiss chard dry matter after pre-incubation for 28 days was similar to that from urea application. Conclusion Findings from this study suggest that duckweed is a resource with beneficial use for nutrient supply to vegetables, especially when appropriate rates are used with pre-incubation.

South African Journal of Plant and Soil, 2018

Effects of long-term application of pig slurry (PS) on soil organic carbon (SOC) pools, nutrients... more Effects of long-term application of pig slurry (PS) on soil organic carbon (SOC) pools, nutrients and maize tissue composition under continuous conventional tillage in a maize-soyabean rotation system in subhumid subtropical environments are unclear. The soil and plant parameters have important implications for PS management under intensive agriculture. Soil (0-20 cm depth) and maize tissue were sampled from lands treated with PS for 0, 10 and 20 years and analysed for soil chemical properties and plant nutrients. Soil available phosphorus, potassium, copper and zinc and tissue concentrations increased due to PS application. Total nitrogen and SOC declined, whereas soil microbial biomass carbon (MBC), hot-water-soluble carbon (HWSC) and microbial quotient (MB/SOC) increased with PS application period. The SOC was negatively correlated to MBC and HWSC (r = −0.472 and −0.663, respectively). Increase in MBC, MBC/SOC and HWSC indicated presence of an untenable soil organic matter with limited possibility of carbon sequestration. The findings imply that long-term PS application, with conventional tillage, not only increased most plant nutrients but also vulnerability of SOC.

Land Degradation & Development, 2019

Most of rural South Africa is semi arid, experiencing a variable climate with extreme weather eve... more Most of rural South Africa is semi arid, experiencing a variable climate with extreme weather events such as droughts and floods. Communal farmers experience problems of getting reliable weather information. Datasets used to describe climate change and variability rely on spatially interpolated gridded data from a few weather stations. The ability of gridded climate data to describe climate variability at the local level has been widely questioned. Communal farmers have developed indigenous strategies to cope with these extremes in order to sustain agricultural production. The objective of this study was to document indigenous strategies that smallholder farmers in Bergville and Msinga, in KwaZulu Natal Province, use to predict weather, conserve soil and water, and manage climate extremes events. Data were gathered through key informant interviews, focus group discussions, and questionnaire. Results showed that more farmers in Msinga than Bergville observed reduced rainfalls and increased temperatures as an indicator of climate variability (p<.05). Bergville and Msinga communal farmers use indigenous indicators such as wind and cloud patterns, animal and bird behaviour, moon shape, and position of the sun to predict weather. Communal farmers using manure were 0.17 times more likely to conserve soil and water when compared with those using artificial fertilizer (p<.05). Thus, indigenous knowledge system (IKS) can be used to conserve soil and water and manage climate extremes and variability. Communal farmers also resist adopting unfamiliar strategies that are forced on them without proper engagement. Communal farmers have managed to survive extreme weather events using IKS.

Journal of Agronomy and Crop Science, 2019

The biomass allocation pattern of plants to shoots and roots is a key in the cycle of elements su... more The biomass allocation pattern of plants to shoots and roots is a key in the cycle of elements such as carbon, water and nutrients with, for instance, the greatest allocations to roots fostering the transfer of atmospheric carbon to soils through photosynthesis. Several studies have investigated the root to shoot ratio (R:S) biomass of existing crops but variation within a crop species constitutes an important information gap for selecting genotypes aiming for increasing soil carbon stocks for climate change mitigation and food security. The objectives of this study were to evaluate agronomic performance and quantify biomass production and allocation between roots and shoots, in response to different soil water levels to select promising genotypes for breeding. Field and greenhouse experiments were carried out using 100 genotypes including wheat and Triticale under drought-stressed and non-stressed conditions. The experiments were setup using a 10 × 10 alpha lattice design with two replications under water stress and non-stress conditions. The following phenotypic traits were collected: number of days to heading (DTH), number of productive tillers per plant (NPT), plant height (PH), days to maturity (DTM), spike length (SL), kernels per spike (KPS), thousand kernel weight (TKW), root biomass (RB), shoot biomass (SB), root to shoot ratio (R:S) and grain yield (GY).

Water Environment Research, 2018

Studies focusing on manipulation of growth conditions for duckweed Wolffia arrhiza to promote bio... more Studies focusing on manipulation of growth conditions for duckweed Wolffia arrhiza to promote biomass for crop nutrient supply, are scarce. The effects of swine lagoon water (SLW) concentration and its replenishment and harvest regimes on selected properties of W. arrhiza were investigated. Dry matter and average growth rate of W. arrhiza were not affected by SLW replenishment periods, whereas the properties decreased with increasing concentration of SLW. The carbon and carbon/nitrogen content increased as the period between solution replenishment increased and as SLW concentration declined from 15 to 5%. Harvesting regimes did not affect the nitrogen content and uptake of duckweed, NH þ 4-N, and mineral-N of SLW. Harvesting duckweed once per week resulted in higher growth rate and biomass, compared with twice a week. Findings from this study suggest that W. arrhiza cultured on 10% SLW and harvested once a week yields biomass with nitrogen content suitable for crop nutrient supply. Water Environ. Res., 90, 2066 (2018).