The study was aimed to provide information on local biomass development during crop growth using ground based optical sensors and to incorporate the local crop status to a crop growth simulation model to improve understanding on inherent variability of crop field. The experiment was conducted in a farmer’s field located near Princeton in Caldwell County, Western Kentucky. Data collection on soil, crop and weather variables was carried out in the farm from 2006 December to 2008 October. During this period corn (Zea mays L.) and winter wheat (Triticum sp) were grown in the field. A 450 m long representative transect across the field consisting of 45 locations each separated by 10 m was selected for the study. Soil water content was measured in a biweekly interval during crop growth from these locations. Measurements on crop growth parameters such as plant height, tiller count, biomass and grain yield were able to show spatial variability in crop biomass and grain yield production. Crop reflectance measured at important crop growth stages. Soil water sensing capacitance probe was site specifically calibrated for each soil depth in each location. Various vegetation indices were calculated as proxy variables of crop growth. Inherent soil properties such as soil texture and elevation were found playing a major role in influencing spatial variability in crop yield mainly by affecting soil water storage. Temporal persistence of spatial patterns in soil water storage was not observed. Optimum spatial correlation structure was observed between crop growth parameters and optical sensor measurements collected early in the season and aggregated at 2*2 m2 sampling area. NDVI, soil texture, soil water storage and different crop growth parameters were helpful in explaining the spatial processes that influence grain yield and biomass using state space analysis. DSSAT was fairly sensitive to reflect site specific inputs on soil variability in crop production.

The object of study – spring barley (Hordeum vulgare L.) and winter wheat (Triticum aestivum L.). Research tasks: 1. To investigate the effect of growing intensity, applying fertilisers according to normative for target yield, on spring barley and winter wheat leaf index, biomass and grain yield formation. 2. To quantitatively assess accumulation of nitrogen and carbon in the biomass during vegetation. 3. To explore the effect of water and nitrogen induced stresses on productivity of photosynthesis and to evaluate feasibility of DSSAT v4.0.2.0 model for the diagnosis. 4. To estimate likely effect of climate change on winter wheat and spring barely yield. / Darbo uždaviniai: 1. Ištirti skirtingo auginimo intensyvumo, tręšiant pagal normatyvus planuojamam derliui, poveikį vasarinių miežių ir žieminių kviečių lapų indekso, biomasės ir grūdų derliaus formavimuisi. 2. Nustatyti kiekybinius azoto ir anglies kaupimosi biomasėje pokyčius vegetacijos metu. 3. Ištirti vandens ir azoto trūkumo sukeltų stresų pasireiškimą migliniuose javuose ir įvertinti galimybes juos diagnozuoti modeliu DSSAT v4.0.2.0. 4. Įvertinti tikėtiną klimato kaitos poveikį žieminių kviečių ir vasarinių miežių derlingumui. Tyrimų objektas – vasarinis miežis (Hordeum vulgare L.), žieminis kvietys (Triticum aestivum L.).