Author
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TAPELA, MATABA - IOWA STATE UNIVERSITY |
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Colvin, Thomas |
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Submitted to: Soil & Tillage Research
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 7/11/2001 Publication Date: 8/23/2001 Citation: TAPELA, M., COLVIN, T.S. QUANTIFYING SEEDBED CONDITION USING SOIL PHYSICAL PROPERTIES. SOIL & TILLAGE RESEARCH. 2001. V. 64. P. 203-210. Interpretive Summary: Every year, farmers around the world strive to produce the 'best' seedbed condition for their crops to grow and thrive. Seedbed preparation usually involves some form of soil manipulation using tillage tools. The tilth created by each tool depends on both the type of implement used and the soil condition. At present, it is not possible to predict the resulting soil condition from any tillage operation. Therefore, famers depend on subjective methods to evaluate whether a prepared seedbed is adequate. The research undertaken here explores ways of using soil physical properties to evaluate seedbed conditions and to develop an index that can help farmers make management decisions. The index combines soil properties such as bulk density, penetration resistance, and moisture content into a single-value soil condition index using statistical methods. The soil condition index is then related to corn grain yield and early plant growth to predict the suitability of a soil to support growth. The index gives promising results in predicting biomass but was not helpful in predicting grain yield for the 2000 season. Long-term results are however necessary to make sure the model does not capture only the one-time response of the crop to a specific set of soil conditions. A valid soil evaluation procedure (index) would be one that can be used to quantitatively select the type of implement to use under given soil conditions to achieve an optimal seedbed condition with minimum possible energy input. This would eliminate the unnecessary costs incurred by farmers using aggressive tools to achieve what could be done by lower disturbance tools. Technical Abstract: The physical condition of soil following tillage influences crop yield, but the desired condition cannot be adequately evaluated with current techniques. Known evaluation procedures are qualitative rather than quantitative. This study was conducted to determine a valid soil condition index (SCI) that could be used to select the type of implement needed to achieve an optimal seedbed with minimum energy input. Effects of proctor density ratio (PDR), moisture ratio (MR), and penetration ratio (PR) resulting from three tillage systems (no-till, chisel plow, and moldboard plow), on the growth of corn (Zea mays L.) were studied. The experiment was conducted in Boone County, Iowa on soils that are mostly Aquic Hapludolls, Typic Haplaquolls and Typic Hapludolls with slopes ranging from 0 to 5%. The average 2000 corn grain yield at this site was 9.36 Mg/ha. At the V2 corn growth stage, the average dry biomass was 1.34 g/plant for all plots. The multi-linear regression correlation of yield against PDR, MR and PR had an R2 of 0.49 (p- value=0.127). There was a significant multi-linear correlation (R2=0.85) between the ratios and biomass. Coefficients for PDR and MR contributed significantly to a regression model between the three ratios and biomass. PR did not have any significant effect (p-value = 0.921), possibly due to it's high correlation with proctor density ratio (r = -0.76), and so was left out of the final model. An analysis of variance showed a significant differences among mean SCI for each treatment (p-value = 0.001). SCI appears to sufficiently model the effect of PDR, MR on corn biomass at V2 stage. This may improve the tillage decision-making process. |
