Microclimate simulation of climate change impacts in a maize canopy

Effects of possible climate modification on maize plant features have been evaluated by using the simulation model of Goudriaan for local climatic conditions and locally measured plant characteristics. Moderate climate modifications were hypothesized. According to the purpose of detecting local impacts of climate change, researches were made on the microclimate of maize canopies. In the energy transport of the plant stand, no shift has been experienced to the direction of the latent heat as it was expected because of the effect of warming up and decrease of precipitation. The changes of stomatal resistance and inside canopy air temperature suggested that the natural water supply will probably not cover the water demand of the plant, if the climate change is more intensive, therefore farmers must prepare to irrigated cultivation and to apply different agro-technical methods to save the water supplies of the ground

Radiation balance components of maize hybrids grown at various plant densities.

Components of the energy and heat balances were examined in two maize hybrids grown at three different plant densities (40, 70 and 100 thousand plants per hectare). One of the hybrids was drought tolerant, while the other was bred for cultivation under irrigated conditions. An increase in plant density influenced not only the size of the leaf area, but also the distribution of the leaves at various plant heights. The extinction coefficient, which provides a quantification of radiation penetration, was higher in the irrigated treatments. By contrast to the other two treatments, the plant canopy in the thinly sown stands remained open throughout the vegetation period, and thus behaved quite differently to the closed stands, making it impossible to compare them. Smaller albedo values were recorded for the hybrid bred for irrigation and in thinly sown stands. The low plant density allowed more energy to reach the soil, from which it was reflected, making a considerable contribution to the final temperature in the stand. The latent heat, in keeping with the quantity of water transpired, was the greatest in the densely sown stands. There was little difference between the latent heat values of the normal and dense stands in either hybrid, indicating that they both had a similar sensitivity to increased stand density. If sufficient water is available it would appear that the stand density could be increased even for the drought-tolerant hybrid

Impact of simulated airborne soot on maize growth and development

Various effects of the dry deposition of soot on maize were investigated in Keszthely (Hungary) in two consecutive years. In order to be able to study a wider range of weather conditions, some of the plants were placed in a Thorn-thwaite-Matter type evapotranspirometer and given ad libitum water supplies. Pollution with airborne black carbon was simulated throughout the season by distributing rates of 3 g·m–2 a week using a motorised dust sprayer. Among the plant growth parameters, the leaf area index was increased by 3% - 14%, depending on the year, suggesting that the plants were able to absorb the carbon settling on the leaves. The black carbon reduced the albedo of the canopy by 17.5% - 21.8%, depending on the year, forcing the polluted maize to absorb more energy. Part of this surplus energy was utilised for increased evapotranspiration (3.9% and 11% in the two years) and to raise the surface temperature of the canopy by 1°C - 2°C during the mid-day hours. The effect of the contamination on maize was more intense in the hot, dry year. The unfavourable effect of soot on maize fertilisation could be observed as a significant increase in the number of deformed ears, leading to a reduction in grain dry matter. The reduction in dry matter yield for polluted maize grown with irrigation in the evapotranspirometer was far less severe than that on non-irrigated plots, suggesting that irrigation was the most obvious solution for mitigating the negative effects of contamination with airborne soot

CORRECTION OF GLOBAL AND REFLEX RADIATION VALUES MEASURED ABOVE THE LAKE BALATON

Albedo measurements have been carried out since 2007 above the Lake Balaton near Keszthely and Siofok. It turned out that a systematic offset error was superposed to both the global and the reflex radiation. The value of this systematic error was approximately constant per pyranometer within a year but on the other hand it varied from year to year and from pyranometer to pyranometer. In this paper the values of this systematic errors were determined with two different methods. The difference between the values measured at night-time and the intrinsic thermal offset error of pyranometers were examined with both methods. The base of the first method is the empirical observation, that the values measured at night-time by a global radiometer are typically negative whereas by a reflex radiometer are typically positive. The substance of the second method is utilizing the air temperature measured within 1 as well as 5 hours before the radiation measuring to +select the fully overcast nights, when the thermal offset error of the global radiometer is zero. In addition, the cases where the thermal offset error of the reflex radiometer is zero were selected on the basis of the difference between water and air temperature. When the thermal offset error is zero the measured value is equal to the systematic error. Comparing the results of the two methods showed that the systematic error of the global radiometer were determined with uncertainty of 1 Wm–2, whereas that of the reflex radiometer with uncertainty of 2 Wm–2. The calibration constants were recalculated from the values being in the calibration reports taking the systematic errors into account

Relationship between seed harvesting method and seed physiological quality for a number of Pioneer maize hybrids

The seed germination and seed vigor of eight Pioneer Hi-Bred maize hybrids were evaluated immediately after harvesting and a year later. The aim was to determine whether the seed showed loss of germination and vigor when shelled mechanically. The seed was cleaned but not dressed, and then germinated according to the ISTA standard procedure in four seed analysis laboratories. In addition, the seed of two randomly chosen hybrids was divided into four fractions based on size and shape, and the germination of each fraction was examined separately. All the germination results were acceptable according to the ISTA (2010) standard (over 90%), but a higher germination percentage was observed after manual shelling than after mechanical shelling. The number of abnormal seedlings, however, was higher for mechanically shelled seeds than for those harvested as whole ears. When the seed of separate seed fractions was tested, the germination percentage was lowest for the medium-sized round fraction and highest for the large flat fraction. The seed vigor of three of the hybrids was highest when maize seeds were harvested shelled rather than on the ear. For all the hybrids the germination percentage was lower for both groups when analyzed a year after harvesting. Better germination results were obtained for all the hybrids after whole ear harvesting than in the shelled group, but the difference was not significant. In the vigor tests the results obtained for mechanically shelled seed were superior to those for whole ear harvesting for the same three hybrids, but again the difference was not significant. The experiments should be repeated over several years to determine whether mechanically shelling maize seed negatively affects seed germination and vigor

Effect of black caarbon on the growth, development and evapotranspriration of maize

Abstract. The effect of soot on certain parameters of maize was analysed. We applied low rates of soot (3 gm–2week–1) with a motorised sprayer. The effect of soot on evapotranspiration was tested on plants grown in evapotranspirometer (ET). Soot pollution had no influence on maize growth and development. Leaf withering after full maturity, however, was delayed by the presence of soot. The ability of soot to absorb irradiation and thus increase leaf surface temperatures led to an increase of 4% in the annual evapotranspiration sum. Soot pollution reduced dry matter (DM) on the rainfed plots (8.8 %), but not in the ET tanks. In the ET tanks, soot had no significant influence on either the stalk or the grain DM, though slight reductions were recorded. On the non-irrigated plot there was 12.4 % reduction in grain dry matter in response to pollution. Supplementary water supplies mitigated the plant damage caused by soot. A further advantage was detected in the number of deformed ears

Comparison of parametric and non-parametric time-series analysis methods on a long-term meteorological data set

In the present explorative study, different time-series analysis methods, such as moving average, deterministic methods (linear trend with seasonality), and non-parametric Mann–Kendall trend test, were applied to monthly precipitation data from January 1871 to December 2014, with the aim of comparing the results of these methods and detecting the signs of climate change. The data set was provided by the University of Pannonia, and it contains monthly precipitation data of 144 years of measurements (1,728 data points) from the Keszthely Meteorological Station. This data set is special because few stations in Hungary can provide such long and continuous measurements with detailed historical background. The results of the research can provide insight into the signs of climate change in the past for the region of West Balaton. Parametric methods (linear trend and t-test for slope) for analyzing time series are the simplest ones to obtain insight into the changes in a variable over time. These methods have a requirement for normal distribution of the residuals that can be a limitation for their application. Non-parametric methods are distribution-free and investigators can get a more sophisticated view of the variable tendencies in time series