The response of roots and biomass yield of soybean and maize seedlings to different levels of soil compaction
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Date
2011
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Abstract
Two factorial experiments were carried out in a greenhouse at the Soil Research Institute, Kwadaso, Kumasi to investigate the response of roots and biomass yield of maize and soybean seedlings to different levels of soil compaction.
The treatments in each of the experiments comprised five levels of soil compaction, using bulk density as an index of compaction, and three varieties each of soybean (Glycine max L.) and maize (Zea mays L.). The experimental set up was a completely randomized design (CRD) with three replications.
The soybean and maize were grown in a stack of three polyvinyl (PVC) cylinders filled with the test soil and consisted of top, middle and bottom cores with a height of 2.5cm, 5cm and 8cm respectively. The test soil, Asuansi Series (Ferric Acrisol) was equilibrated to a constant gravimetric moisture content of 18% and uniformly compacted in the cylinders to the desired bulk densities of 1.1, 1.3, 1.5, 1.7 and 1.9 Mg m-3. The middle cores, to which the five compaction treatments were applied, were sandwiched between the top and bottom cores each of which had a bulk density of 1.1 Mg m-3. The three cores were sealed together into one air-tight and water-tight soil container by wrapping them with a plastic tape.
The soil parameters measured were bulk density, total and air-filled porosity, saturated hydraulic conductivity and field capacity. The plant parameters, measured 15 and 21
days after planting (DAP) of soybean and maize respectively, comprised plant height, root and shoot dry mass, root length, root penetration ratio and root:shoot ratio. The data were analyzed statistically for ANOVA using SAS software and regression analysis was used to establish the correlation between parameters and to produce predictive equations.
Total porosity and air-filled porosity generally decreased as bulk density increased with the former and latter ranging from 28.3 to 58.5% and -4.46 to 27.09% respectively at the bulk densities of 1.9 and 1.1 Mg m-3. Air-filled porosity was more sensitive to soil compaction.
Saturated hydraulic conductivity varied between 25.6 and 44.2 mm h-1 under bulk densities of 1.9 and 1.1 Mg m-3 respectively. The hydraulic conductivity decreased by 6.6, 12.9, 32.6 and 42.1 percent as bulk density increased from 1.1 to 1.3, 1.5, 1.7 and 1.9 Mg m-3. Moisture content at field capacity (FC) decreased as bulk density increased with a value of 17.24 and 28.55 percent for the 1.9 and 1.1 Mg m-3 respectively.
Soil compaction, crop variety and their interactions significantly (P<0.05) influenced the measured plant parameters of soybean and maize. Increases in bulk density generally caused significant decreases in all the measured plant parameters except the root : shoot ratio which increased. The significant differences (P<0.05) were generally recorded between the lower (1.1 to 1.5 Mg m-3) and higher (1.7 and 1.9 Mg m-3) bulk densities.
Description
A thesis submitted to the Board of Postgraduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirements for the award of the Degree of Master of Science in Soil Science, 2011