Untitled - MendelNet 2013 - Mendelova zemědělská a lesnická ...

MENDELNET 2013Evapotranspiration rate (mm/hour)0.60.50.40.30.20.1ET barleyETo grassETo alfalfaMay June July00:00 6:00 12:00 18:00 0:00 6:00 12:00 18:00 0:00 6:00 12:00 18:00 0:00-0.1Fig 2 Mean actual (ET) and reference (ETo) evapotranspiration rate (mm/hour) of grassland andalfalfa for individual months.Tab 1 Mean Kc of barley for particular months calculated for grass and alfalfa and the correlationcoefficient describing the relation between actual and reference ET.Kc (ETo grass) Kc (ETo alfalfa) r – grass x barley r - alfalfa x barleyMay 1.17 1.03 0.92 0.91June 1.16 1.03 0.96 0.96July 0.55 0.48 0.65 0.61CONCLUSIONSThe crop coefficients for spring barley were calculated and analyzed in this study. We can concludethat at the beginning of growing season the Kc reflected more bare soil that real crops. This wasmainly due to rainy weather in May and June. On the other hand, dry July together with lowertranspiration of ripe crops caused decrease in ET of barley. Potential ETo was, however, high andso Kc declined. Our assumption that ET will correlate better with ETo of alfalfa was not confirmed.However, further study is planned to determine whether Kc calculated using ETo of alfalfa will bemore stable that the one of grass. The object of further study remains also, correlation of thedifferences between ETo based on grass and alfalfa to VPD or ratio between VPD and aerodynamicresistance.REFERENCESAllen R. G., Pruitt W. O., Wright J. L., Howell T. A., Ventura F., Snyder R., Itenfisu D., StedutohP., Berengena J., Yrisarry J. B., Smith M., Pereira L. S., Raes D., Perrier A., Alves I., Walter I.,Elliott R. (2006): A recommendation on standardized surface resistance for hourly calculation ofreference ETo by the FAO56 Penman-Monteith method. Agricultural Water Management 81: 1–22.Allen R. G. (2003): Crop coefficients. Encyclopaedia of Water Science, DOI: 10.1081/E-EWS120010037.Bowen I.S. (1926): The ratio of heat losses by conduction and evaporation from any water surface.Physical Review, 27: 779–787.Bréda N. J. J., (2003): Ground-based measurements of leaf area index: a review of methods,instruments and current controversies. Journal of Experimental Botany, 54 (392): 2403–2417.Fischer M. (2012): Water balance of short rotation coppice, Mendelu Brno. Ph.D. thesis: 261 pp.361 | P age