engleski

The soil potassium resources and the efficiency of potassium fertilizers in Croatia

Agricultural land capacity in Croatia is 3, 208 mill. ha. Of this, there are 2, 02 mill. of cultivable land, 1, 446 mill. ha of arable land and gardens, 71000 ha of vineyards, 70, 000 ha of orchards, 310, 000 ha of meadows and 1, 155 mill. ha of pasture lands. Ponds, marsh-lands and fisheries take up 33, 000 ha. The area of cultivable land at 0.42 ha per capita. According to geographical characteristics, there are three regions in Croatia: the Mediterranean or the Adriatic region, the Mountainous region and the Pannonian region. Croatia has a characteristics temperate climate with four well-defined seasons. Summers are not unbearably hot, bitter cold weather is rare, and when is occurs it only last for a short time, while spring and fall are pleasant. There are three types of climate: temperate continental climate, mountainous climate and Mediterranean climate. Precipitation reaches 700-1000 mm along the coast, and rises up to 2000 mm in Like and Gorski Kotar regions ( the mountainous part of Croatia). In the lower continental parts of Croatia precipitation reaches 800-1200 mm in the northwest and less than 800 mm in the east. Average temperature in January is usually between 0 and -2 oC in the continental part of Croatia. In general, it is in range from -4 oC (the highest positions of the mountainous region) to 8 oC (the islands of central and southern Dalmatia and southern Dalmatian coast). Average temperature in July vary between 20 o and 22 oC in the northern and eastern parts of Croatia as well as in the Adriatic hinterland, while in the coast and on the islands, the temperatures exceed 23 oC. Only over 500 m above sea-level are the temperatures lower than 20 oC. In Croatia, there are two parallel agricultural production systems. The first has very large units and modern mechanization, and produces a few crops, and uses large quantities of mineral fertilizers and pesticides. The second kind is the small agricultural unit that concentrates on stock-rearing and produces a wide range of produce (these are private-owned concerns). There are in total 534, 000 of private farms and 400 of large units (ex-social sector). Average farm size is 2.94 ha and 1160 ha, respectively. Average fertilizer use (kg/ha of arable land: status of 1991) is 69 and 310, for small agricultural units and large units, respectively: it is considerably lower compared to the European average. Phenomenon of reduced fertilizer consumption in Croatia is in accordance with the global trend of world fertilizer consumption. Peasant holdings are the fundamental organizational form of agricultural production in Croatia. They own 77.8% of the cultivable land and total livestock numbers, and over nine tenths of the total numbers of tractors and of the work-force. over two million people live upon them, or 45% of the total population of Croatia). In 1991, majority of all private holdings (in total 69%) were 3 ha or less in size, and only 5.6% of them were bigger than 8 ha. Maize and wheat are the most spread cereals (they occupies in mean 33% and 22% of total arable land capacities, resp.), while sugar beet, soybeans and sunflowers are the most spread industrial crops. Testing of soil properties, including plant available K status, was made only for needs of state farms, while private land was tested in very moderate amount. For example, it is estimated that in Eastern Croatia at was analyzed about 48 % of agricultural land in property of the state farms and only 4 % of private land (in total 128, 000 ha). Estimation of plant available K (determination by the AL-method) status is as follows (mg K2O/100 g of soil): <10 = 18%, from 10 to 20 = 52%, from 20 to 30 = 22% and >30 = 8%. However, in the other part of Croatia status concerning share of soil testing is less favourable in comparison with status in Eastern Croatia. Also, routine soil testing was left to decision of agrocombinates concerning both quantity and dynamics. Unfortunately, this activity has without state support in frame of state scientific project as many other European countries. Testing of plant K status was made mainly as part of scientific investigations (plant samples of field and pot experiments with inclusion of fertilization treatments or genetic investigations, testing of nutritional disorders). Additional problem is absence of publishing of soil test data in the scientific and professional journals. For this reason, the authors of this study utilized in the main personal communications as the way of data collection. In general, K availability status of soil in Croatia is estimated as satisfied, but they were found examples of acute K deficiency in area of Sava and Drava valley. Growth retardation and chlorosis of maize and soybean plants were observed when these crops were grown on some drained gleysols. Also, the moderate symptoms of K deficiency were found in wheat plants (edge necrosis of leaf tissue) but wheat plants were more tolerant to soil stress in comparison with maize and soybean. Four experimental fields with increased K fertilization were conducted in the period from 1984 to 1990. Application of enormous rates of potassium in form of KCl (60% of K2O) was indicated by the previous soil and plant testing. Potash (60% K2O) was added in increased amounts (K2O/ha) to levels of 1105 kg (locality Gundinci), 990 and 3200 kg (locality Cerna), 2670 kg (locality Stari Mikanovci) and 2400 kg (locality Crnac polje). In the next years, it was used only ordinary fertilization (N, P and K) of the experimental fields. The soils of these experimental fields are heavy clay soils because clay is dominant soil fraction with share above 40 % (Gundinci and Cerna) and 35 % (Stari Mikanovci). High contents of fixing clay minerals such as mixed layer and vermiculite were found by the rentgenographic analysis. Due to the increased K fertilization (exp. field Gundinci), grain yield of maize increased from 4.98 t/ha (ordinary treatment) to 8.96 t/ha (the first year of testing) and from 5.30 t/ha to 6.71 t/ha (the third year of testing). Application of K fertilizer resulted in maize grain yield increases up to 23 % (two-year mean). Already with the lowest K rate, the grain yield was increased by 52 % (exp. field Cerna). Grain yields increased in range of 87 % and 42 % as affected by K and P fertilization, respectively (exp. field Crnac polje). When both these elements were added in the ameliorative amounts, than grain yield of maize increased for 55 % compared to ordinary fertilization. Grain yields of soybeans were increased by 40 % and 34 % as affected by K and P fertilization, as well as by 22 % when both of these elements were added in the ameliorative amounts. In the exp. field Stari Mikanovci, it was applied even to 2670 kg K20/ha Economic analysis of the data indicates that K fertilization was very profitable. The additional expense of the K fertilization (even the highest rate of K: 2670 kg K20/ha) was recovered in the first year of the experiment. For example, the cost of this amount of K was equivalent to the price of 3.51 t of maize grain on the Croatian market in autumn of 1987. In this study, maize grain yields were increased by 7.13 t/ha in the first season following this level of K fertilization. The analogous comparison for soybean is 1.17 t of grain and 1.27 t/ha, respectively. Increase of K fertilization (in the some cases in combination with P fertilization) is direction for soil fertility improvement on K deficient soils of Eastern Croatia. Although application of the enormous rates of K fertilizer was profitable, for practical purpose our recommendations are applications of lower amounts of K fertilizers. For example, for practice acceptable solution could be using of ameliorative K fertilization about 500 kg K2O/ha of every year. We presume that band placement of fertilizer is more effective compared with broadcast fertilization. For this reason, part of ordinary K fertilization (for example, 150-200 kg of granulated KCl fertilizer) should be added simultaneously with sowing in form of band placement. Also, ameliorative K rate could be distributed in band instead of broadcast. In the most cases these soils are heavy structure (prevailing of clay fraction) and it is impossible deep depositions of fertilizer simultaneous with sowing. In these cases, our recommendation is fertilization immediately before sowing. The agricultural knowledge system in Croatia is composed of three fundamental components: agricultural education and training, agricultural research and the transfer of knowledge into practice. Although there are many institutions in this area, and although they are widely spread, the level of synergy is very low. The Advisory Service is currently undergoing reorganization within the framework of the Agriculture Ministry. Now it is organized as a special sector of the Ministry. For the moment it is envisaged that the sector will employ 118 people. It is organized in each one of 21 counties, where there is a local branch with from 4 to 7 advisors. The main tasks envisaged for the service are education, training in new methods, and giving advice about technical and economic problems. Apart from this, the Advisory Service should act as an information service for this Ministry, and convey to it information about problems faced by farmers, about the research programs needed, and all other needs. The Advisory Service is financed out of the Ministry budget. Soil and plant testing laboratories in function of agricultural production improvement have been established in frame of agricultural faculties and scientific institutions, as for example are agricultural institutes as independent organization and scientific units in frame of some agrocombinates. Majority of these laboratories are now out of function due to different reasons as follows: war destruction (for example, laboratories of Faculty of Agriculture Osijek and Agricultural Institute Osijek), closing down because of financial reasons (laboratories in frame of former agrocombinates Zupanja and Vinkovci ). Also, remaining laboratories are in serious difficulties due to considerably decreased of orders for chemical analysis as affected by economic crisis and insolvency of agricultural companies and private farms.

soil; potassium; fertilizers; Croatia

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