Milan Poljak

Mulching decreases nitrate leaching in bell pepper (Capsicum annuum L.) cultivation

A 2-year study was conducted in the Vrana Valley (Mediterranean region of Croatia) to evaluate the effects of application of different mulching materials and drip-fertigation on nitrate leaching in bell pepper (Capsicum annuum L.) cultivation. Nitrate–N leaching from the root zone of bell pepper was compared in three treatments: control without mulch, with black polyethylene (PE) mulch and with biodegradable cellulose mulch. In the first year, the highest quantities of nitrogen were leached in the treatment without mulch (26 kg ha � 1 ) following by the treatment with cellulose mulch (18 kg ha � 1 ) and the lowest nitrogen leaching (10 kg ha � 1 ) was observed in the treatment with black PE mulch. At the end of the harvest, cellulose mulch, a microbiologically degradable material, started to decompose and disintegrate, which resulted in the cellulose mulch treatment behaving similarly than the control treatment without mulch. In the second year, significant leaching occurred after the last harvest in September. As the bell pepper yield was significantly lower than expected and calculated for fertilisation, the crop did not take up all nitrogen supplied by fertilisation, which resulted in higher concentrations of nitrate in the soil solution. These nitrate concentrations were subjected to leaching caused by precipitation, a regular occurrence in the autumn and winter in this region. However, mulched surfaces showed lower quantities of nitrate leached in comparison with the treatment without mulching. Mulching with black PE film, besides producing higher yields, reduces the leaching of nitrate fertilisers, and combined with fertigation can reduce a potential risk of surface and ground water pollution by nitrate.

Aiuminium tolerance of durum wheat germplasm

SummaryAluminium tolerance of Macedonian durum wheat (Triticum turgidum L. conv. durum (Desf.) MacKey) germplasm was evaluated in nutrient solutions containing 0, 74 or 148 μM of total Al. Relative root length (148 μM Al/0 Al) of various genotypes ranged from 41 to 72% (from moderately sensitive to moderately tolerant to Al). No genotype with Al tolerance close to that of very tolerant T. aestivum cultivar Atlas-66 was found. Seed Ca concentration was positively (r=0.64, P≤0.05) and seed Fe concentration negatively (r=−0.71, P≤0.05) related to the relative root growth. Such a significant correlation was not obtained for seed concentrations of other nutrients or seed protein content.

Effects of nitrogen nutrition on potato tuber composition and yield

Field fertilization trials were set up at private farm in Slovinska Kovacica, one of major region for processing potato production in Croatia. The effect of five nitrogen rates (0, 100, 150, 200, 250 kg ha-1) and three potato cultivars (Solanum tuberosum L.) during three growing seasons on tuber mineral composition, dry matter content and total tuber yield were studied. Tuber nitrogen concentrations differed significantly and great impact of growth condition and cultivar on tuber mineral composition was shown. Total tuber yield increased significantly with increasing N rate, but there was no significant difference between 100 and 250 kg ha-1 N rates. Increasing N rates have no significant effect on dry matter content or mineral composition of tuber but significant positive correlation (r=0.34*) between tuber N vs. Ca concentration was determined.

Efficiency of use of chlorophyll meter and Cardy-ion meter in potato nitrogen nutrition

One of the biggest challenges for the safe maize production is the yield stability in a wide range of environments with different soil fertility, weather conditions, prevailing pests and diseases as well as cultural practices. In order to achieve it, new hybrids with higher tolerance to biotic and abiotic stress are continuously being created. In order to compare performance of maize hybrids in environments with different levels and types of stress, and relate it to the stalk lodging incidence, we compared performance of 64 maize hybrids obtained by crossing 16 inbred lines with four inbred testers in three different environments. Two environments at same location (Rugvica) differed in crop rotation, and the third environment at location Botinec was considered as dry because of low water capacity of the soil. Mixed models that included all design elements and genetic background of hybrids were used to analyze the effect of lodging on yield in different environments. The results show that stalk lodging had a significant effect on yield, but significant lodging x environment interaction indicates that this effect was rather environment specific.Sweet pepper Istra F1 hybrid was grown in a greenhouse on K rich soil. For evaluation of K antagonism, two K rates (55 and 85 kg ha-1) were applied in a randomized complete block design with four replications. Total number of fruits, total number of BER affected fruits as well as average fruit mass were recorded for each harvest. Fruit and leaf K and Ca content were determined at three plant growth stages (at the stage of the first, third and fifth fruit cluster). Higher K rate gave higher : average fruit mass (169.45 g), total number of fruits per plant (7.95), number of BER affected fruits per plant (3.82), K in leaves (5.44% DM), K in fruits (6.35% DM), but negatively correlated with Ca concentration in fruits (0.57% DM) and leaves (3.24% DM). This resulted in decreased marketable yield of sweet pepper fruits.

Flower sterility and the germination ability of pollen as genetic traits of seven olive (Olea europaea L.) cultivars grown in Croatia

Summary To evaluate and use olive (Olea europaea L.) cultivars appropriately, studies on their reproductive biology are necessary. The proportion of staminate flowers and the success of pollen germination in olive were found to vary depending on cultivar, climatic conditions, and the site of cultivation. In this study, floral gender and pollen germination were analysed to assess the reproductive potential of seven olive cultivars in Croatia. The percentages of staminate flowers and pollen germination in four Croatian (‘Drobnica’, ‘Lastovka’, ‘Levantinka’, and ‘Oblica’) and three Italian (‘Itrana’, ‘Leccino’, and ‘Pendolino’) olive cultivars were determined over six flowering seasons in three orchards. We observed variable numbers of flowers per inflorescence in the different cultivars. The proportion of staminate flowers ranged from 2.6% (‘Leccino’ in 2006) to 66.0% (‘Oblica’, 2009), and fluctuated with cultivar, year, and orchard. ‘Leccino’ and ‘Pendolino’ developed lower percentages of staminate flowers than ‘Lastovka’, ‘Levantinka’, and ‘Oblica’ in most experimental years. Higher fruit set was observed for cultivars with lower percentages of staminate flowers, indicating that olive tree productivity depends on the number of fully developed flowers. We found significant differences in the extent of pollen germination between the various cultivars, orchards, and germination media used. Pollen germination varied from 2.1% (‘Lastovka’ in 2006) to 31.6% (‘Oblica’ in 2005). ‘Oblica’ and ‘Levantinka’ showed significantly higher percentages of pollen germination than ‘Leccino’ and ‘Pendolino’. There was no difference in the order of cultivars analysed according to their proportions of staminate flowers and the success of pollen germination between the orchards at Mravince and Kastela. Our results suggest that the level of pistil abortion, and the success of pollen germination, are genetically determined and are most likely an evolutionary adaptation to redistribute available resources.

Effects of organic and mineral fertilization on NPK status in soil and plant, and yield of red beet ( Beta vulgaris var. conditiva )

Two-year field fertilization trial with red beet (Beta vulgaris var. conditiva) was carried out at two locations in Croatia. The trial was set up according to the Latin square method with four fertilization treatments (5 kg m-2 stable manure, 50 and 100 g m-2 NPK 5-20-30 and unfertilized control). In most cases the highest soil P and K content was obtained in the treatment with stable manure or 100 g m-2 NPK 5-20-30. A similar situation as in the soil was also obtained in plants. The highest N, P, K contents in 2003, and also P and K in 2004 in red beet were determined in the treatment with stable manure. Comparison of yields per fertilization treatment shows that the control treatment gave the lowest yield in both years. The highest yield in 2003 was determined in the treatment with stable manure (0.99 kg m-2) and there was no significant difference in comparison with the 100 g m-2 NPK treatment (0.82 kg m-2). Although there were no significant differences in 2004 between fertilization treatments, the relatively highest yield (4.59 kg m-2) was determined in the treatment with 100 g m-2 NPK. Such wide variations are probably a consequence of weather conditions.

Quantification of aluminum-induced changes in wheat root architecture by X-ray microcomputed tomography

ABSTRACT Root architectural traits are of fundamental importance for plant performance, especially under unfavorable soil conditions. This study examined the effect of aluminum (Al) toxicity in different growing media (nutrient solutions and soil) on root architecture of two wheat (Triticum aestivum L.) cultivars with different Al tolerances. Seedlings were grown in acidic and limed soil and in two contrasting nutrient solutions. Root systems of soil-grown plants were scanned using x-ray microcomputed tomography (µCT) while that of nutrient solution–grown plants were assesses using WinRhizo, 3 and 5 days after planting (DAP), respectively. Aluminum caused significant reduction of all examined root traits (number of seminal roots, root length, length of the longest seminal root, root surface area, and root volume). Growth in acidic soil caused significant reduction in root length, length of the longest seminal root, and root surface area at 5 DAP. Soil-grown plants produced a larger root system compared to plants grown in nutrient solutions. Aluminum toxicity–induced differences of root traits were also found between different nutrient solutions. Beside the well-known reduction of root length, Al toxicity had a profound effect on other root architectural traits. X-ray µCT has revealed root architectural changes under specific conditions of acidic, Al-toxic soil. Differences obtained in Al-induced effects on root architecture between different nutrient solutions as well as between different growing systems emphasize the need for further study of root architecture, especially under specific conditions of Al toxicity in acidic soils.

DISTRIBUTION OF CADMIUM AND ZINC IN DIFFERENT FRACTIONS OF GLEY-AMPHIGLEY SOIL

Distribution of Cd and Zn in different soil fractions was determined by the method of sequential partial extraction after Tessier on drained gley-amphigley soil in the period 1997-1999. The trial comprised three treatments with three replications: control (0.0 mg Cd and 0.0 mg Zn kg-1 soil), Cd2Zn4 (2.0 mg Cd and 4.0 mg Zn kg-1 soil) and Cd2Zn0 (2.0 mg Cd and 0.0 mg Zn kg-1 soil). Research results show significant differences in the distribution of Cd and Zn in different fractions in dependence on trial treatments and sampling time. In the control treatment, the largest part of total Cd (> 60%) was bound in the residual fraction and the Fe and Mn oxide fraction, whereas in the treatment with Cd in the exchangeable fraction (30 to 38%) and the Fe and Mn oxide fraction (35 to 41%). The highest concentration of exchangeable Cd (46.9-49.7% of total Cd) was recorded 20 days after treatment and the lowest during the last sampling, 150 days post treatment. Zinc was most abundant in the residual fraction (> 80%) regardless of trial treatments and sampling time.

Gas exchange capacity of Croatian common bean landraces (Phaseolus vulgaris L.) is related to their origin and growth type

The long tradition of common bean (Phaseolus vulgaris L.) cultivation in Croatia has resulted in the development of many landraces, which create a valuable basis for screening different physiological traits. Studying gas exchange parameters could provide valuable information that could be useful in creating new crop germplasm with enhanced agronomic attributes. Variability of gas exchange parameters, such as the net photosynthetic rate (A), transpiration rate (E), stomatal conductance (gs), intercellular CO2 concentration (Ci), light use efficiency (LUE), and water use efficiency (WUE) were studied on the collection of 226 common bean accessions and the relationship of the gas exchange parameters with the origin and morphological traits was tested. The highest variability among all landraces was found for the WUE and gs, and lowest for the A and LUE traits, indicating high potential of these traits to be used for selection and breeding programs. Accessions of the Mesoamerican origin had higher A and LUE and lower Ci values compared to accessions of the Andean origin. Accessions with the determinate growth had higher gs and Ci values and lower A, LUE and WUE values compared to accessions with the indeterminate growth. The variance components analysis showed that the growth type has a more pronounced effect on gs, Ci and WUE, whereas the origin has a stronger impact on A and LUE. The principal component analysis (PCA) showed that A separates accessions according to their origin, whereas Ci separates accessions according to their growth type. Accessions with higher Ci had lower A, indicating possibly higher rates of carboxylation per active site on Assist. Prof., PhD, Boris Lazarević, Department of Plant Nutrition, Faculty of Agriculture, University of Zagreb, Svetošimunska cesta 25, HR-10000 Zagreb, Croatia, tel: +385 1 2393961, e-mail: blazarevic@agr.hr * This work has been fully supported by the Croatian Science Foundation under the project UIP-11-2013-3290.

The effect of boron on growth and development in strawberry (Fragaria ananassa Duch.) shoot culture

The effect of boron was tested on three strawberry (Fragaria ananassa) cultivars: Korona, Elsanta and Gorella. Boron was added into the culture medium as boric acid (H3BO3) with the concentration ranging from 0.0 to 8.68 mg B L-1, and the medium was solidified with 0.8% agar. A liquid medium without B was tested, also. The tested B concentration did not affect the time of shoot appearance but affected the number of newly developed shoots at the multiplication phase of culture. Regardless of the B quantity added to the medium in the rooting phase, the time of appearance and the number of rootlets did not differ in the same cultivar. Strawberry plantlets in axenic culture were tolerant of high B quantities in a medium, but they also survived in a medium with no boron added. Increase of B concentration to eight times the amount in MS (Murashige and Skoog) nutrient medium did not provoke necrosis nor inhibit shoot growth. The B concentration in plantlets reflected the increase of B concentration in the medium.