The mode of inheritance of yield, topping height, leaf number, days to flowering, leaf length and width was studied by means of graphic analysis in a half diallel cross test of four burley tobacco varieties (Saturn, TN 86, Bs 92 and Bols 100) in 1998 and 1999. The trial was set up according to the RCBD at four replications in the experimental field of Tobacco Institute Zagreb in Pitomača. Overdominance in inheritance of all studied traits, except leaf length and width in 1998, was found by the graphic method. No interallelic interaction and epistasis were present as seen from testing regression coefficients for all investigated traits and years. The distribution of parental genotypes on a sca�er diagram along the expected regression line points to the genetic divergence of the parents. Parent Bs 92 appeared to have the most dominant alleles for yield and leaf length and parent Saturn for topping height, leaf number and leaf width.

The conception of these investigations is based on the premise that a way should be found to eliminate, or at least mitigate, the harmful effect of excessive soil acidity without resorting to the massive and costly measures of liming. The main issue addressed in this study is how to increase crop yield by increasing nutrient availability rather than how to neutralize the soil. This as well as our earlier investigations, conducted on pseudogley of mesoelevations, indicate that this can be achieved by the application of special natural amendments (SNA) based on zeolite tuff, under the name Agrarvital (AV), in which clinoptilolite prevails while the remaining part is a mixture of soft lithothamnian limestone and dolomite (SLL+D). These amendments enhance ion exchange in the soil and their activation at a considerably lower pH than it is the case after liming. Fertilizing value of Agrarvital (AV) and lime materials (LM) was evaluated according to the yields achieved and some yield components of the crops grown. The results point to the good fertilizing effect of AV upon yields of winter wheat, maize, soybean and winter barley, equal to or better than the effect of conventional LM applied at several times higher rates.

Subapical ears are largely responsible for grain yield variations in prolific maize (Zea mays L.) grown under conditions favourable for the expression of prolificacy trait, but limited information exists on yield components contributing to yield responses. A field experiment was conducted to determine the yield components of apical and subapical ear in prolific maize after various pollination treatments at two plant populations. Hybrid Pioneer 3733 was grown in the perfect stands of 71 428 and 35 714 plants ha )1 . Three pollination treatments were carried out: (i) free pollination; (ii) subapical earshoots were covered to prevent pollination; and (iii) apical earshoots were covered to prevent pollination. Grain yields of free pollinated plants were by 50.1 % larger at low plant population (265 g per plant) than at high plant population (177 g per plant) due to a 45.3 % increase in kernels per plant, whereas 1000-kernel weight slightly increased by 3.3 %. These increased kernels per plant at low plant population were, in part, the result of kernel increments on apical ear (10.1 %), and mainly associated with kernels from subapical ears that did not occur at high plant population. At low plant population, the total grain yield per plant was reduced by 94 g (35.5 %) after the apical ear was bagged to prevent pollination, but only 52 g (19.6 %) when the subapical ear was bagged. When subapical ear development was stopped at low plant population, grain yield on apical ears increased by only 3.9 % as a result of heavier 1000-kernel weights, clearly demonstrating limitations in kernel set and size. After grain development on apical ear was prevented, subapical ear enlarged to 80.3 % of maximum apical ear yield because the former had, on average, 2.5 % lighter 1000-kernel weight and 17.5 % fewer kernels than the latter. Ears did not differ in row number when only apical or subapical ear was developed on plant, whereas subapical ears tended to have fewer rows than apical ears when both were present on the same plant. Our results showed that: (i) plant population affected all yield components on both apical and subapical ear except row number; (ii) the occurrence of subapical ear is triggered by achieving maximum potential kernel set on apical ear; and (iii) subapical ear is inferior in potential grain yield to apical one even when the latter was prevented from pollination.

No abstract

The harvest time of fibre flax is influenced by climatic conditions, varieties, stages of maturity and the crop's final use. In addition, the time of harvesting of fibre flax affects the quality of the fibres. Fibre flax can be harvested in few stages of maturity. So, this paper presents the influence of three stages of maturity (green, yellow and full ripening) on the agronomic traits (stem yield, stem yield after retting, total fibre yield, share of total fibre, long fibre yield, share of long fibre) of five fibre flax varieties. Varieties trials with fibre flax were set up in two years (2010-2011) and in two locations: at the experimental fields of the Faculty of Agriculture in Zagreb on eutric cambisol and of the College of Agriculture at Križevci on pseudogley on level terrain. The trials were carried out according to the randomized complete block design (RCBD) with four replications. According to the results of the two-years research into the agronomic traits of fibre flax, significant differences were established among the varieties and among the stages of maturity under study. The varieties Agatha, Viola and Electra recorded higher values of investigated traits. All varieties achieved higher values of investigated traits at Križevci (production on heavier soil in which some of winter moisture remained available in spring months). The highest values of investigated traits were recorded when the fibre flax were harvested in the green ripening.