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Intercropping is not fancied in high input agriculture of developed countries but it is widely practiced in the agriculture of developing countries. It is now being accepted that well managed intercropping systems are stable and sustainable. An ecophysiological model using the Fortran Simulation Environment (FSE) was used to simulate the leaf area growth of an intercropping system of immature-rubber, banana and pineapple under potential crop growth conditions. The leaf growth for each crop was smimulated based on the amount of dry matter partitioned to the leaves after after respiratory losses were discounted from individual crop light interception and carbohydrate assimilation of the intercrop. At 600 days after planting (DAP) the simulated leaf index (LAI) of rubber and pineapple was on average 1.4 respectively. The simulated LAI for the parent crop of banana was about 4.3 at peak growth (150 DAP), and at the same time the simulated LAI of the first ratoon crop was about 2.7. The mean absolute error (MAE) between simulated and observed LAI for rubber, mother banana, first ratoon banana and pineapple was 7.7%, 15.2%, 27% and 6.4% respectively. This indicates that the leaf area index was simulated with good accuracy but there is scope for improvement.

This study was conducted to investigate the effect of rotary tillage on some soil physical properties (bulk density, cone index, plasticity index, aggregate uniformity coefficient) and organic matter, and to develop and evaluate a soil tilth index based on changes of these soil properties. The tillage treatments were 4×3 factorial combinations of forward speeds obtained with four selected tractor transmission gears (Gear 1 High, Gear 2 Low, Gear 3 Low and Gear 4 Low), and three rotary tilling speeds (140 rpm, 175 rpm and 200 rpm) of commonly used tillage implements in Malaysian paddy fields. Experimental results indicated a significant decrease in bulk density of the soil due to rotary tillage. The other soil parameters were not significantly affected by the tillage operation. Analysis of variance indicated significant difference (p<0.01) among the rice yield means. Bulk density was identified to have a high positive correlation with the rice yield. A tilth index consequently developed with bulk density, cone index and plasticity index gave better predictability (r2= 0.56) of rice yield than when individual soil properties were considered. Results of the study suggest that tilth index may assist in yield prediction by comparing measured soil conditions in a paddy field.

Seedbed preparation for lowland rice cultivation consumes considerable amount of energy. To reduce the energy expenditure for seedbed preparation, tillage treatment combinations of tractor forward speeds achieved with four transmission gear selection (Gear 1 High, Gear 2 Low, Gear 3 Low and Gear 4 Low) and three rotary tilling speeds (140 rpm, 175 rpm and 200 rpm) were studied. The cost of seedbed preparation was computed and benefits of the tillage treatment over control (Gear 3 Low and rotary tilling speed of 140 rpm) compared. Almost for every treatment, except Gear 2 Low and rotary tilling speed of 200 rpm, the energy input was lower than the control, making an energy saving to an extent of 0.5% to 33.8% and time saving of 3.3% to 35.4%. the cost of seedbed preparation was observed to linearly increase with increase in the total time spend for seedbed preparation. The minimum cost was for Gear 1 High and rotary tilling speed of 175 rpm and maximum cost was for the control. The benefit was maximum for Gear 1 High and rotary tilling speed of 175 rpm and minimum for Gear 2 Low and rotary tilling speed of 175 rpm. The result of the study suggest the adoption of Gear 1High and rotary tilling speed of 175 rpm for seedbed preparation under lowland rice cultivation.

Spreadsheets are now widely used for data entry and analysis. Therefore, Texture AutoLookup (TAL) is a computer program designed to work within 1–2–3 for Windows and EXCEL to determine the USDA soil textural class. TAL determines the textural class without having to repeat data entry because data is taken directly from the spreadsheet itself. Moreover, TAL works even with two particle size data or with imperfect data (that is, the sum of the three particle sizes being unequal to 100%). TAL is independent of the particle‐size analysis method, and TAL allows textural class names to be modified or be translated into another language.

The purpose of this study were: 1) to compare the aggregate stability of individual aggregate size fractions, 2) to determine the interrelationship and efficiency of several aggregate stability indices, and 3) to determine the relationship and importance of organic matter and other soil constituents on aggregate stability. To compare the aggregate stability of individual aggregate size fractions, a mathematical model was developed to estimate the breakdown of individual aggregate size fractions in the wet-sieving (using nested sieves) method. This model was validated and calibrated by comparing the estimation values to the actual aggregate breakdown values by paired sample t-test, linear regression and prediction error sum of squares. The average percentage of stable aggregates for all aggregate size fractions were represented in an index called average intact aggregates (AlA). Factor analysis was used to determine the interrelationship and efficiency of several aggregate stability indices. Aggregate stability of eight soil samples were measured with eight indices: percentage of water-stable aggregates >0.3 mm (WSA >0.3) and >0.5 mm (WSA >0.5), AlA, water-dispersible clay (WDC), waterdispersible clay and silt (WDCS), mean weight diameter after wet-sieving (MWDw), turbidity percentage (TP), and clay ratio (CR).