SEGH Articles

SEGH2018 Prize Winners Series: Mumba Mwape

20 August 2018
Winner of a Best Poster Prize at SEGH2018: Selection and design of irrigation systems in Zambia - this installment of the Prize Winners Series is contributed by Mumba Mwape.

 

Mumba R. Mwape1, Derek M. Heeren2,3, Dean Eisenhauer3, Aaron Mittelstet2,3 and Laszlo Hayde4

1: Zambia Agricultural Research Institute, Zambia, 2: University of Nebraska-Lincoln, USA, 3: Robert Daugherty Water for Food Global Institute, USA, 4: IHE-Delft Institute for Water Education, Netherlands

Zambia has been making various reforms aimed at improving the agriculture sector for the past two decades. Recent developments have seen a streamlined focus on irrigation as a means of increasing production and productivity to bring about sustainability in the agriculture sector, which had previously been dependant on rainfall. These efforts have been directed at small-scale farmers who have been impacted by reduced rainfall due to climate variability. The high cost of irrigation equipment and the urgent need to increase food production entails that irrigation plans guarantee sustainability, effectiveness and efficiency. This research was aimed at evaluating the suitability and viability of community irrigation systems, and designing systems for two sites (of 60 ha each) in Masaiti and Samfya in agro-ecological region III of the country using surface (river) and ground (well) water sources respectively.

 

 Field infiltration test (taking readings)

 

In establishing the suitability of the areas, soil tests such as infiltration and texture analyses were conducted as well as the depth of the soils. The quality of water was assessed for different parameters for toxicity levels that may restrict water use in irrigated agriculture. To determine the quantity of water, a pumping test was carried out for ground water while 20 year monthly flow rates of the river were used for surface water. Land and water availability were also assessed. Aquacrop was used to determine the crop water requirements and the yield potentials and based on the yield potential results, the most profitable crops with the least water requirements were selected. The soil tests showed high infiltration rates of 10 cm/hr and 11.6 cm/hr for Masaiti and Samfya respectively. This led to the recommendation of only sprinkler and drip irrigation systems. The pumping test gave a potential yield of 110 l/s while the river’s 20-year average flow rate gave 2 m3/s and 26.6 m3/s as the lowest and highest rate respectively. The quality of the water from both sites was found to have no restriction to agricultural use according Food and Agriculture Organization (FAO) standards. The crops selected, for a 60 ha irrigation system, had a water requirement of 50.8 l/s when water is not limited and 34.5 l/s if staggered planting dates are used. This water requirement can be supplied by both sources that were analysed, up to 2 irrigation systems by the well and 9 irrigation systems if 25% of the river’s lowest flow rate is diverted for use. The land tenure system in the area is customary and farm sizes per household was between 5->50 ha and while cultivation was less than 10% of the total area owned. The economic analysis of the irrigation development for a center pivot and drip irrigation system gave a positive outlook with an improvement in yield of 65% to more than 100% and with a profit margin per ha approximately 10 times more than the profit of current production practices.  

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Latest on-line papers from the SEGH journal: Environmental Geochemistry and Health

  • Editorial 2018-12-11
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    Abstract

    Samples of PM2.5 were collected from an urban area close to a national highway in Agra, India and sequentially extracted into four different fractions: water soluble (F1), reducible (F2), oxidizable (F3) and residual fraction (F4) for chemical fractionation of arsenic (As), cadmium (Cd), cobalt (Co), chromium (Cr), nickel (Ni) and lead (Pb). The metals were analyzed by inductively coupled plasma optical emission spectroscopy in each fraction. The average mass concentration of PM2.5 was 93 ± 24 μg m−3.The total concentrations of Cr, Pb, Ni, Co, As and Cd in fine particle were 192 ± 54, 128 ± 25, 108 ± 34, 36 ± 6, 35 ± 5 and 8 ± 2 ng m−3, respectively. Results indicated that Cd and Co had the most bioavailability indexes. Risk Assessment Code and contamination factors were calculated to assess the environmental risk. The present study evaluated the potential Pb hazard to young children using the Integrated Exposure Uptake Biokinetic Model. From the model, the probability density of PbB (blood lead level) revealed that at the prevailing atmospheric concentration, 0.302 children are expected to have PbB concentrations exceeding 10 μg dL−1 and an estimated IQ (intelligence quotient) loss of 1.8 points. The predicted blood Pb levels belong to Group 3 (PbB < 5 μg dL−1). Based on the bioavailable fractions, carcinogenic and non-carcinogenic risks via inhalation exposure were assessed for infants, toddlers, children, males and females. The hazard index for potential toxic metals was 2.50, which was higher than the safe limit (1). However, the combined carcinogenic risk for infants, toddlers, children, males and females was marginally higher than the precautionary criterion (10−6).

  • Effects of steel slag and biochar amendments on CO 2 , CH 4 , and N 2 O flux, and rice productivity in a subtropical Chinese paddy field 2018-12-07

    Abstract

    Steel slag, a by-product of the steel industry, contains high amounts of active iron oxide and silica which can act as an oxidizing agent in agricultural soils. Biochar is a rich source of carbon, and the combined application of biochar and steel slag is assumed to have positive impacts on soil properties as well as plant growth, which are yet to be validated scientifically. We conducted a field experiment for two rice paddies (early and late paddy) to determine the individual and combined effects of steel slag and biochar amendments on CO2, CH4, and N2O emission, and rice productivity in a subtropical paddy field of China. The amendments did not significantly affect rice yield. It was observed that CO2 was the main greenhouse gas emitted from all treatments of both paddies. Steel slag decreased the cumulative CO2 flux in the late paddy. Biochar as well as steel slag + biochar treatment decreased the cumulative CO2 flux in the late paddy and for the complete year (early and late paddy), while steel slag + biochar treatment also decreased the cumulative CH4 flux in the early paddy. The biochar, and steel slag + biochar amendments decreased the global warming potential (GWP). Interestingly, the cumulative annual GWP was lower for the biochar (55,422 kg CO2-eq ha−1), and steel slag + biochar (53,965 kg CO2-eq ha−1) treatments than the control (68,962 kg CO2-eq ha−1). Total GWP per unit yield was lower for the combined application of steel slag + biochar (8951 kg CO2-eq Mg−1 yield) compared to the control (12,805 kg CO2-eq Mg−1 yield). This study suggested that the combined application of steel slag and biochar could be an effective long-term strategy to reduce greenhouse gases emission from paddies without any detrimental effect on the yield.