Abstract

CADENA-ZAPATA, Martín; CANTU-SIFUENTES, Mario; CAMPOS-MAGANA, Santos  and  RIOS-CAMEY, Mario. A model to estimate an upper soil workability limit as function of texture and organic matter. Terra Latinoam [online]. 2010, vol.28, n.4, pp.297-305. ISSN 2395-8030.

It is important to determine the highest soil moisture content at which soil can be worked to avoid risk of degradation by compaction. In this research a statistical model was developed to relate upper workability limit (UWL) with soil texture and organic matter (OM) concentration. Soil samples of different textures and OM were sieved to use the aggregate fractions of 2.8 to 4 mm at consistencies from dry soil to plastic soil. Samples were then compacted up to 400 kPa to simulate agricultural machinery loads; immediately an air permeability test was performed to determine the area of pores. The reference value at which the compaction occurs was 1 × 10^-12 m² and at this value the soil water content was the UWL of a particular soil. A multiple regression analysis indicated that clay, silt and OM concentration of the soil were the variables that best predicted the UWL. An R² = 0.996 indicated that the variables explain 99% of the model variability. The OM concentration had the main effect in predicting the UWL and clay had an effect almost double that of silt. In the random part of the model, the variance in the residuals was constant; there were neither problems of normality nor serial correlation of the errors. The results of cross validation indicated that the model has good stability because the average prediction error was 2.29, which indicates good accuracy for the UWL predictions.

Keywords : statistical model; tillage; soil moisture.