J. Pivec

Analysis of the potential evapotranspiration demands in the Czech Republic between 1961-1990

Dynamics of the evapotranspirational demands in the Czech Republic within three decades from 1961 to 1990 has been studied. The determination of the levels of influence of the respective natural components depends on the regionalized modelling techniques. The project of regionalized modelling is theoretically based on the potential evapotranspiration values (ET0) calculated by FAO methodology (eqs. 1, 2) and the series of temperature and rainfall observations obtained by climatologic stations during a 30-year period from 1961 to 1990 and its relation to the absolute altimetric. The DMR-2 military digital elevation model of the Czech Republic relief consisting of a regular network of points with their altitudes specified in meters was used for the purpose of regionalized modelling. One step of the network in the S-42 coordinate system with the Gauss conforms cylindrical projection is equal to 100 meters; this implies that the smallest area for which the data can be processed is 1 hectare. The digital relief model can be linked to both direct (temperature, precipitation) and derived (evapotranspiration) quantities, which is one of the many novelties of regionalized modelling. The climatic data used in regionalized modelling records daily measurements were obtained by 85 climatologic and rainfall-monitoring stations from 1961 to 1990. Our results showed an appreciable decrease of the most drying area (ratio P/ET0 up to 0.755) in the last decade 1981–90; half as less amounts compared with the previous decade 1971–80 (about 500,000 hectares). On the other hand, an apparent increase (more than 500,000 hectares in comparison with the previous decade 1971–80) of the wettest area (ratio P/ET0 over 1.508) through the last decade was observed. Both first decades 1961–70 and 1971–80 look similar. The project mentioned in this article has made it possible to create models for the different time intervals which have showed higher reliability for heterogeneous application.

Effect of row width on splash erosion and throughfall in silage maize crops

Brant V., Zábranský P., Škeříková M., Pivec J., Kroulík M., Procházka L. (2017): Effect of row width on splash erosion and throughfall in silage maize crops. Soil & Water Res., 12: 39−50. Line width is one of the major factors affecting arable soil erosion. The aim of the study was to assess the effects of different row spacing on splash erosion and throughfall in maize crops. Field measurements of the throughfall (Pth, mm) and splash erosion (MSR, g/m 2) were carried out in silage maize crops (row spacing 0.45 and 0.75 m) in 2012–2014. The BBCH growth stages for the crops, plant length (L, m), and leaf area index (LAI) were evaluated. Positive correlation was observed between the aerial precipitation (P, mm) and the Pth values. With increasing P-values, higher levels of Pth were identified in the 0.75 m compared to the 0.45 m row spacing. The value of this proportion was decreasing from the centre of the inter-row (0.75 m) to the row of the plants direction. Statistically significant lower values of splash erosion were observed in the 0.45 m compared with the 0.75 m wide rows, especially within the years 2012 and 2014. The experiments proved the positive influence of the length of plants and LAI on P/Pth values. A decrease of Pth in relation to precipitation values with height of plants and LAI values was observed. This dependency was then confirmed from the beginning of the stem elongation (BBCH 30) to the end of flowering (BBCH 70). Tighter dependency between the plant length (L) and the values of P/Pth ratio in the 0.75 m wide crop rows was determined. Conversely, a more important influence of LAI on the values of P/Pth ratio was estimated in the 0.45 m wide crop rows. The experiments proved the positive influence of the 0.45 m wide rows on the decrease of splash erosion as well as throughfall compared with the 0.75 m row spacing.

Splash erosion in maize crops under conservation management in combination with shallow strip-tillage before sowing

Brant V., Kroulík M., Pivec J., Zábranský P., Hakl J., Holec J., Kvíz Z., Procházka L. (2017): Splash erosion in maize crops under conservation management in combination with shallow strip-tillage before sowing. Soil & Water Res., 12: 106−116. Soil under maize cropping is among the most endangered by erosion. The effect of conservation tillage management on values of splash erosion when using shallow strip tillage before sowing maize was evaluated in the Central Bohemian region (Czech Republic) during the period 2010–2012. The following types of tillage management using conventional technology and shallow tillage were evaluated: ploughed plots with mulch formed by weed biomass (PLW), ploughed plots with mulch from perennial ryegrass plants (PLPR), ploughed plots without mulch (PL) and shallow tillage (ST) where the mulch was formed by cereals straw. Furthermore, values of the splash erosion, plants and plant residues coverage ratio of soil by image analysis and the stability of soil aggregates were monitored during the whole experiment. The average value of splash erosion (MSR) was higher by 18.7% in the variant of PLW, lower by 35.9% in PLPR, and lower by 39.5% in ST, than in the control treatment PL (MSR value for PL = 100%) for the whole evaluated period (2010–2012). The average values of the soil surface plant coverage ratio in the plots with mulch ranged from 1.5 to 43.0% at the beginning of the vegetation period, and from 4.9 to 85.5% in the second half of the vegetation period. A positive correlation was observed between the average values of the stability of soil aggregates and the plant coverage ratio of the soil surface in 2010 and 2011.

Evapotranspiration and Transpiration Measurements in Crops and Weed Species by the Bowen Ratio and Sapflow Methods Under the Rainless Region Conditions

The aim of this chapter is to provide a systematic description of the measurements of total evapotranspiration and transpiration of selected agricultural crops and weeds, results of investigation, and perspectives of these methods for agricultural usage. This study provides a contribution towards increased knowledge on the consumptive water use of arable crops and weeds within the temperate climatic zone under specified weather conditions and actual crop structure given by biometric observation. The water consumption of plants represents a significant part of the landscape water balance (Merta et al. 2001). An important factor influencing the water balance of the plant stands on agricultural soil and thereby in the countryside is the species composition of phytocoenosis. Within the framework of phytocoenosis, the cultivated plants and weeds take share in influencing the water balance (Pivec & Brant 2009). Competition between plants to capture the resources essential to plant growth (i.e. light, water and nutrients) is one of the key processes determining the performance of natural, semi-natural and agricultural ecosystems (Kropff & van Laar, 1993). The issue of evapotranspiration and transpiration demands of field crops is a subject of intensive study especially in arid and semi-arid areas. In terms of eliminating the negative impact of agriculture on the environment and in terms of increasing the efficiency of the production systems, its monitoring is important for the temperate climate as well.