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.

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.

Keep up to date

Eldoret, Kenya

06 July 2020

## 37th SEGH International Conference: Geochemistry for Sustainable Development

Nanjing City, China

09 November 2020

30 December 2020

## SubmitContent

Members can keep in touch with their colleagues through short news and events articles of interest to the SEGH community.

## Science in theNews

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

• Distribution of metal(loid)s in particle size fraction in urban soil and street dust: influence of population density 2020-01-18

### Abstract

Assessment of street dust is an invaluable approach for monitoring atmospheric pollution. Little information is available on the size distribution of contaminants in street dusts and urban soils, and it is not known how the population density would influence them. This research was carried out to assess the size distribution of trace metal(loid)s in street dust and urban soil, and to understand how population density might influence the size-resolved concentration of metal(loid)s. Three urban areas with a high, medium and low population density and a natural area were selected and urban soil and street dust sampled. They were fractionated into 8 size fractions: 2000–850, 850–180, 180–106, 106–50, 50–20, 20–10, 10–2, and < 2 µm. The concentration of Pb, Zn, Cu, Cd, Cr, Ni, As, and Fe was determined, and enrichment factor and grain size fraction loadings were computed. The results indicated that the concentration of Pb, Zn, Cu, Cd, and Cr was highly size dependent, particularly for particles < 100 µm, especially for street dust. Low concentrations of Ni and As in street dust and urban soil were size and population density independent. Higher size dependency of the metals concentration and the higher degree of elemental enrichment in the street dust fractions than the urban soils indicate higher contribution of human-induced pollution to the dust. Findings also confirm the inevitability of size fractionation when soils or dusts are environmentally assessed, particularly in moderately to highly polluted areas. Otherwise, higher concentrations of certain pollutants in fine-sized particles might be overlooked leading to inappropriate decisions for environmental remediation.

• Soil–plant system and potential human health risk of Chinese cabbage and oregano growing in soils from Mn- and Fe-abandoned mines: microcosm assay 2020-01-17

### Abstract

In Portugal, many abandoned mines are often close to agricultural areas and might be used for plant food cultivation. Soils in the vicinity of two Mn- and Fe-abandoned mines (Ferragudo and Rosalgar, SW of Portugal) were collected to cultivate two different food species (Brassica rapa subsp. pekinensis (Lour.) Hanelt and Origanum vulgare L.). Chemical characterization of the soil–plant system and potential risk of adverse effects for human health posed by plants associated with soil contamination, based on the estimation of hazard quotient (HQ), were assessed in a microcosm assay under greenhouse conditions. In both soils, the average total concentrations of Fe and Mn were above the normal values for soils in the region and their concentration in shoots of both species was very high. Brassica rapa subsp. pekinensis grew better in Ferragudo than in Rosalgar soils, and it behaved as an excluder of Cu, Mn, Fe, S and Zn in both soils. The HQ for Cu, Fe, Mn and Zn in the studied species grown on both soils was lower than unit indicating that its consumption is safe. The high Mn tolerance found in both species might be due in part to the high contents of Fe in the soil available fraction that might contribute to an antagonism effect in the uptake and translocation of Mn. The obtained results emphasize the need of further studies with different food crops before cultivation in the studied soils to assess health risks associated with high metal intake.

• Concentration, fractionation, and ecological risk assessment of heavy metals and phosphorus in surface sediments from lakes in N. Greece 2020-01-13

### Abstract

The presence of phosphorus (P) and heavy metals (HMs) in surface sediments originating from lakes Volvi, Kerkini, and Doirani (N. Greece), as well as their fractionation patterns, were investigated. No statistically significant differences in total P content were observed among the studied lakes, but notable differences were observed among sampling periods. HM contents in all lakes presented a consistent trend, i.e., Mn > Cr > Zn > Pb > Ni > Cu > Cd, while the highest concentrations were recorded in Lake Kerkini. Most of the HMs exceeded probable effect level value indicating a probable biological effect, while Ni in many cases even exceeded threshold effects level, suggesting severe toxic effects. P was dominantly bound to metal oxides, while a significant shift toward the labile fractions was observed during the spring period. The sum of potentially bioavailable HM fractions followed a downward trend of Mn > Cr > Pb > Zn > Cu > Ni > Cd for most lakes. The geoaccumulation index Igeo values of Cr, Cu, Mn, Ni, and Zn in all lakes characterized the sediments as “unpolluted,” while many sediments in lakes Volvi and Kerkini were characterized as “moderately to heavily polluted” with regard to Cd. The descending order of potential ecological risk $$E_{\text{r}}^{i}$$ was Cd > Pb > Cu > Ni > Cr > Zn > Mn for all the studied lakes. Ni and Cr presented the highest toxic risk index values in all lake sediments. Finally, the role of mineralogical divergences among lake sediments on the contamination degree was signified.