This study evaluated the potential of portable spectral camera techniques for measuring cover crop chemical composition in different growth stages. A height measurement system was also developed using a laser distance sensor to predict cover crop biomass. PLS (Partial Least Squares) regression was used to evaluate the relationship between cover crop nutrient content and spectral data. The study revealed that a partial cross-sectional area of canopy had a slightly higher correlation with the cover crop biomass than that of the canopy height. High correlations were observed between the predicted and observed accumulation of N (R2 = 0.8698), Ca (R2 = 0.8512), Mg (R2 = 0.8415) and K (R2 = 0.9451). This method can be used to obtain information on cover crop nutrient accumulation without disturbing cover crop growth.
Spatial and temporal variability of new shoots (number of shoots, dry mass and nitrogen concentration) were investigated under several conditions using precision agriculture technology. The growth and spatial variability of new shoots were both determined using the normalized difference vegetation index (NDVI). At harvest, there were differences in new shoots growth depending on variety, severe shading, and nitrogen fertilizer type. There were differences in new shoot for “Ten-cya” compared to that for “Sen-cya,” and temporal variability of growth had a different tendency compared to spatial variability at harvest depending on several conditions. Coefficients of determination (R2) and root mean square error (RMSE) were established by the NDVI model. The accuracy was R2≥0.826 with RMSE≤15.0 g/m2 for “Sen-cya” and R2≥0.877 with RMSE≤13.6 g/m2 (vegetation coverage ratio ≤ 100%) for “Ten-cya”.
Experiments to measure the vertical dynamic loading forces acting on the track rollers of a half-tracked tractor were conducted by using strain gauges. In addition, a driving simulation model was constructed to predict the vertical dynamic loading forces acting on the track rollers as the tractor ran on an asphalt road surface. A two-dimensional model to evaluate the vibration characteristics of the half-tracked tractor is discussed. It was modified and improved by considering the linear and nonlinear interactions of the rubber crawler with the track roller as well as the roller's location arrangement.
The publisher of "Engineering in Agriculture, Environment and Food (EAEF)" will change from J-Stage (JST) to Elsevier Ltd. on January 1, 2014. New issues after Vol.7 will be browsed on ScienceDirect, whereas Vol.1-6 can be still browsed on J-Stage.
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