Mechanized tillage-induced compaction and its effect on maize (Zea Mays L.) growth and yield—a comprehensive review and analysis

While agricultural engineers are concerned with physico-mechanical properties of arable soils, agronomists tackle crop management husbandry as soil scientists’ dwell on bio-chemical properties. Such diverse and isolated interests seldom report any interaction or integrated effect of biological, agronomical, and physico-mechanical parameters of soils affected by mechanized tillage induced compaction. This paper reviews intrinsic effects of mechanized tillage-induced compaction on soil-water-nutrient dynamics, crop growth, and yield of maize. Mechanized tillage induced top and subsoil compaction are caused by soil-tyre contact stresses and machinery axle loads respectively. Mechanized tillage-induced compaction reduced maize nutrient absorption levels of Nitrogen (N), Potassium (K), Magnesium (Mg), and Sodium (Na) by 13.5%, 51.4%, 50.4% and 51.5% respectively. Maize N uptake was least affected by tillage-induced compaction compared to P and K. Mechanized tillage-induced compaction improved maize root intensity, root mass and volume by over 50% in compacted topsoils but decreased by 90% in the sublayers. Maize root length, fresh and dry root mass, shoot elongation, height, and leaf area index reduced by 29%, 39.1, 37.8, 27.1, 10-21, and 67.8% respectively. In contrast, mechanized tillage-induced compaction improved soil-seed-soil-root contacts, soil-root-bonding root density and diameter, stiffness, anchorage, and root-lodging resistance of maize. Mechanized tillage induced compaction index and bulk density range of 1.5-3.0MPa and 1.2-1.52 Mg/m3 respectively are the critical levels beyond which maize rooting, growth and yield are impaired. Dependent on dynamic soil covariates, viz limiting water range, matrix suction potential and organic matter content; mechanized tillage-induced compaction reduces maize yield by as high as 50%

Research Article Design and Evaluation of Solar Grain Dryer with a Back-up Heater

Abstract: The aim of the study was to design and construct a solar grain dryer integrated with a simple biomass burner using locally available materials. This was to address the limitations of the natural sun drying for example drying exposure, liability to pests and rodents, over-dependence on sun and escalated cost of mechanical dryers. This became beneficial especially in reducing post-harvest losses as well as helping in the preservation of agricultural product. The dryer is composed of solar collector, drying chamber, back-up heater and airflow system. The design was based on the study area of Mau summit located in Nakuru County, Kenya. The average ambient conditions were 26°C air temperature and 72% relative humidity with daily global solar radiation incident on horizontal surface of about 21.6 MJ/m 2 /day. A minimum of 3.77 m 2 solar collector area was required to dry a batch of 100 kg maize grain in 6 h with natural convection from the initial moisture content of 21% to final moisture content of 13% wet basis. A prototype dryer designed was fabricated with minimum collector area of 0.6 m 2 and used in the experiment. Forced convection was employed to reduce drying time. The thermal efficiencies of the solar and solar assisted dryer were 39.9 and 57.7%, respectively. The back-up heating system improved the efficiency of the dryer by 17.8% and reduced drying time substantially