Mr. Monga Mzuku

A study was carried out during 2003 – 2004 with the objective of characterizing the soils of DMP sites. The sites were located at three villages in Bobirwa Sub-district (representing the hardveld) and at two villages in Kgalagadi District (representing the sandveld). All tests were conducted within a transect of 50 m wide and 8000 m long. Soils were characterized at the village sites and in the laboratory for physical, chemical and microbial properties. Soil erosion was monitored using embedded nail technique. Analysis of remotely sensed data of Bobirwa Sub-district was also carried out to assess the risk of land degradation. The data was analyzed using Procedure General Linear Model in Statistical Analysis System. The infiltration rate of sandveld soils (classified as Ferric Arenosols) was significantly (P<0.05) higher (at 150±30 mm/h) than that of hardveld soils (classified as Chromic/Ferric Luvisols and Calcic Cambisols) (at 30±11 mm/h). Sandveld soils also exhibited significant higher bulk density of 1.64±0.04 g/cm³ and lower water storage of 0.21±0.08 m/day compared to hardveld soil mean values of 1.43±0.14 g/cm³ and 0.58±0.20 m/day, respectively. Hardveld soils had a significant higher mean CEC content of 25.0±7.7 meg/100 g throughout the soil profile compared to mean values of 2.64±1.4 and 7.0±2.3 meq/100g for sandveld soils at Tsabong and Tshane, respectively. A similar scenario applied to Ca, Mg, K and soil P. In a span of 30 years in Bobirwa Sub-district, the total land use area increased from 32,000 ha in 1970 to 790,000 ha in 2000 resulting in the reduction of natural vegetation cover from 1,000,050 to 500,050 ha during the period. The cleared land surface areas thus created pose a high risk of land degradation. As these soils have shown to possess stable micro-structure, they can be rehabilitated by biological means such as tree planting and resting of badly degraded borehole areas.

Researchers from Colorado State University, in collaboration with scientists from the United States Department of Agriculture (USDA), initiated a long-term multi-disciplinary study in precision agriculture in 1997. Site-specific management zones (SSMZ) were investigated as a means of improving nitrogen management in irrigated maize cropping systems. The objective was to develop precise nutrient management strategies for semi-arid irrigated cropping systems. This study was conducted in five fields in northeastern Colorado, USA. Two techniques for delineating management zones were developed and compared: SSMZ and yield-based management zones (YBMZ). Nitrogen uptake and grain yield differences among SSMZs were compared as were soil properties. Both management zone techniques were used to divide fields into smaller units that were different with regard to productivity potential (e.g., high zones had high productivity potential while low zones had low productivity potential). Economic analysis was also performed. Based on grain yield productivity, the SSMZs performed better than the YBMZ technique in most cases. Grain yield and N uptake between the low and high productivity management zones were statistically different for most site-years and N fertilizer rates (p<0.05). Soil properties helped to explain the productivity potential of the management zones. The low SSMZ was markedly different from the high SSMZ based on bulk density, organic carbon, sand, silt, porosity and soil moisture. Net returns ranged from 188 to 679 USDha−1. In two out of three site-years the variable yield goal strategy resulted in the largest net returns. In this study, the SSMZ approach delineates areas of different productivity accurately across the agricultural fields. The SSMZs are different with regard to soil properties as well as grain yield and N uptake. Site-specific management zones are an inexpensive and pragmatic approach to precise N management in irrigated maize

Water is the factor most limiting to dryland crop production in Botswana because of low and erratic rainfall and high evaporative demands. Much research work has been done on soil and water management techniques that improve and stabilize crop production in Botswana. Tied-ridging, furrow and precision strip tillage systems increased soil water storage and crop yields on sandy loam soils but did not appeal to farmers due to differences between conventional methods and additional labour and equipment required. Double ploughing was effective in weed control and improving crop yields. Deep tillage and single mouldboard ploughing of loamy and clod-forming soils increased water infiltration and crop yields. Surface residue management and minimum tillage such as chisel ploughing are low input farming systems with a potential for the enhancement of soil moisture conditions in Botswana. The challenge is to ensure large-scale practical implementation of such technologies with a view increase and stabilize crop yields.

The spatial variation of productivity across farm fields can be classified by delineating site-specific management zones. Since productivity is influenced by soil characteristics, the spatial pattern of productivity could be caused by a corresponding variation in certain soil properties. Determining the source of variation in productivity can help achieve more effective site-specific management. The objectives of this study were (i) to characterize the spatial variability of soil physical properties across irrigated corn (Zea Mays L.) production fields and (ii) to determine if soil physical properties could explain the variability in productivity between site-specific management zones. The study was conducted over three study sites in northeastern Colorado. The soil properties measured were bulk density, cone index, surface soil color, organic C, texture, sorptivity, and surface water content. A multi- response permutation procedure was used to test for significant differences among soil properties between management zones. Box plots of soil physical properties were created for each management zone within each study site to determine if trends in soil physical properties corresponded to the productivity potential of the management zones. Overall, this study showed that soil physical properties exhibited significant spatial variability across production fields. The trends observed for the measured soil physical properties corresponded to the productivity potential of the management zones. Utilizing site-specific management zones could help manage the in-field variability of yield- limiting soil physical properties.

Remote sensing allows for the rapid and inexpensive acquisition of soil reflectance data. Knowing what soil parameters have the greatest influence on bare soil imagery will facilitate better use of remote sensing for precision crop management. The objectives of this study were (i) to determine measured soil properties that are most influential on remotely sensed bare soil reflectance and (ii) to select which spectral band or combination of spectral bands is best for describing individual soil properties. This study was conducted on three study sites located in northeastern Colorado. All sites were in irrigated continuous corn (Zea mays L.) cropping systems. Remotely sensed imagery was acquired by aircraft prior to planting. Soil samples were collected and analyzed for bulk density, soil color (moist and dry), organic matter, organic carbon, soil texture, and cone index. Principal component analysis (PCA) was performed for the green, red, and near-infrared (NIR) bands of the imagery. Least-squares regression analysis was used for analyzing relationships between remote sensing data and soil data. Across study sites, the first principal components of the green, red, and NIR bands were found to have significant statistical relationships with organic carbon and sand, silt, and clay fractions. Individual spectral bands explained a significant portion of the variability in soil moisture, moist soil color, dry soil color, organic carbon, sand, silt, and clay. Results from this study support the use of remote sensing for assessment of soil variability.

• Mafimisebi, T.E., M. Mzuku, A.O. Akinrinola, O.A. Thompson, E.O. Mafimisebi and J.F. Obiri. 2017. Feasibility Studies for Agribusiness. p. 13-21. In Obiri, J.A.F., Driver M.F., Onyekwelu, J.C., Akpoko, J.G., Ramasawmy, B and Drame-Yaye, A. (eds.) Agribusiness in Africa. ANAFE, Nairobi