Tuesday, November 14, 2006

Estimation of Expectable Plant Density for Crop Modeling.

Gabriella Mathe-Gaspar1, Nandor Fodor2, and Geza Kovacs2. (1) 1223 Budapest Kisteteny Koz 5, 1525 Budapest PF.35.MTA TAKI, Budapest, 1223, Hungary, (2) 1525 Budapest PF.35.MTA TAKI, 1223 Budapest Kisteteny Koz 5, Budapest, 1223, Hungary

The number of emerged plants is key to a good estimation in crop modeling. Emergence represents the point in time when seedling photosynthetic autotrophism begins and determines the maximum number of plants. The well-known production models e.g. CERES, CROPGRO determine the length of emergence, but they require plant density as an input parameter. Plant density is a critical input data that is used for the calculation of LAI, biomass and crop yield in the models. Optimum conditions of seed germination and emergence have been determined by several authors. They quantified the demands of different plant species for temperature, water and light for germination and emergence. The aim of present work was to substitute plant number as a model input parameter with an estimation to gain a real number of emerged plants. For this purpose we carried out field and pot experiments to study the effect of important parameters (like temperature, water, salt and pH) on seed germination and emergence as they were influenced by cultivation methods, weather, soil density. These factors determined seed emergence in an interaction with each other under field conditions.  To characterize soil conditions three factors were used in the model: “temperature”, “water” and “soil” factors. Values of factors change between 0-1, where 1 represents the optimal condition. Factors of “temperature” and  “water” are simpler; their values are calculated by simple algorithms taken into account of sowing depth and soil density. Factor of “soil” is much more complex. The value of this factor is determined by cultivation methods, sawing depth, date of cultivation, salt content, heavy metal concentration, and pH value.