Application of a simulation model (VARLEACH) for calculation of herbicide distribution in the soil under field conditions. Part 2. Implementation into the expert system HERBASYS
1992
Gottesbueren, B. (Biologische Bundesanstalt fuer Land- und Forstwirtschaft, Braunschweig (Germany). Inst. fuer Unkrautforschung) | Pestemer, W. | Bunte, D.
The implementation of the simulation model VARLEACH (Variable Leaching) into the herbicide advisory system HERBASYS to calculate the herbicide distribution pattern in the plough layer is described. Examples of the practical use e.g. for the prognosis of the efficacy of isoproturon against Alopecurus myosuroides considering the amount and location of the residues in the top soil and the calculation of the dates for split-application to sustain the phytotoxic concentration of chlortoluron against Alopecurus myosuroides in the soil are given. In field experiments on 2 soils the vertical distribution of metribuzin, chlortoluron and methabenzthiazuron were measured in the plough layer (0-30 cm) and the adjacent deeper soil layer (30-40 cm) 13 and 112 days following different types of soil cultivation (deep ploughing 25 cm, shallow plowing 10 cm and harrowing 10-15 cm). Regardless of soil type and herbicide deep ploughing reduced the residual amount in the top-soil layer (0-10 cm) by approximately 90 %, shallow ploughing by appr. 50 % and harrowing by appr. 10 %. Between 13 and 112 days after cultivation metribuzin was more mobile than chlortoluron or methabenzthiazuron. After deep ploughing the maximum herbicide concentration was in the 20-30 cm layer. Shallow ploughing and harrowing distributed the herbicide residues not deeper than 10-20 cm. Empirically derived factors to consider herbicide loss from the top 10 cm layer by deep ploughing (0.9), shallow ploughing (0.5) and harrowing improved the prognosis with HERBASYS of phytotoxic effects to succeeding crops after soil cultivation
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