engleski

Response of field crops to phosphorus fertilization in the Eastern Croatia

Eastern Croatia is a granary of country. Soils of the region are different chemical properties. Moderate P supplies were found in some soils, mainly in luvisol and stagnosols. For this reason, P deficiency symptoms (growth retardation and chlorosis including violet colour) have been found in seed-corn crop, especially during cold and moist spring. Aerial part of chlorotic plants (means of six samples) at 6-8 leaves stage (the growing season 1989) characterized by low dry matter yield (0.84g/plant), low P and Ca contents (0.23% P and 0.34% Ca in dry matter) and excess of Al and Fe (2385 ppm Al and 2937 ppm Fe in dry matter). Also, some drained gleysols situated in Sava river lowland are low supplied by ether K or both with P and K mainly as affected by strong fixing capacities. Four field trials with increased P (in form either single or tripled superphosphate) and K fertilization (as potash) conducted in four replications by randomized block design on these soils during the 1980ies. Increased fertilization was applied only for the first year of testing, while in the next years ordinary fertilization of entire field was made. In general, K application resulted by higher corn and soybeans yield in comparison with P application, while response of wheat was considerably lower. In the first experiment (locality Gundinci), five levels of P until 465 kg P/ha and five levels of K until 917 kg K/ha were applied at autumn 1985. By P applications, the highest corn grain yield was 5.36 t/ha and it was in range of the control (5.06 t/ha), while as affected by K fertilization yields increased until 42% (4-year means). However, wheat yielded similar on all fertilization treatments. In the second experiment (locality Cerna) five levels of P until 406 kg P/ha as triplex at early spring 1986 were applied. By application of 308 kg P/ha grain yield of corn increased from 2.29 t/ha (control: 52 kg P/ha) to 4.50 t/ha or for 97% (2-year means). In the third experiment (locality Mikanovci) P application at autumn 1986 (four levels until 392 kg P/ha) did not influenced on corn grain yield, while by K application (seven levels until 2090 kg K/ha) corn yields increased trifold compared to usual fertilization. In the fourth experiment (locality Vrbje), five rates P (until 1110 kg P/ha) and K (until 2125 kg K/ha) were applied at early spring 1990. Corn grain yields were increased from 3.81 t/ha (control) to 5.40 t/ha (590 kg P/ha) and to 7.13 t/ha (2125 kg K/ha. At same time, soybean yields were increased from 2.13 t/ha (control) to 2.86 t/ha (195 kg P/ha) and to 2.98 t/ha (610 kg K/ha). By the other two experiments increased P fertilization until 588 kg P/ha as superphosphate in combination with liming resulted by either similar or moderate increases (mainly less than 10%) of corn and soybean yields.

phosphorus ; fertilization ; corn ; wheat ; barley

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