THE EFFECT OF VARIOUS KINDS OF NITROGEN F ERTILIZERS ON THE YIELD, NUTRITIVE-VALUE AND MINERAL-COMPOSITION OF COCKS FOOT (DACTYLIS-GLOMERATA L) HERBAGE

In three-year trial with cock's foot in pure culture the effect of var ious kinds of N fertilizers was studied in four-cut use as affected th e mineral composition of herbage. The trial was established on albic l uvisol, medium heavy at an altitude of 470 m above sea level. Detailed meteorological data are in Tabs I and II. The development of agrochem ical soil properties is in Tab. III. The trial consisted of four treat ments with uniform fertilization with Ca, Mg and P. The treatment I us ed ammonium nitrate with limestone (LAV - 27.5% N), treatment II conta ined calcium nitrate (LV - 15% N), treatment III - urea (MO - 46%) and treatment IV - DAM 390 (DAM - 30% N). In all treatments a uniform dos e of 50 kg N.ha(-1) (i.e. 200 kg N.ha(-1) annually) was applied to eac h cut. The herbage was harvested in the first to third cuts at the sta ge close to the onset of heading and in the fourth cut at the stage of full shooting. The results of measurings were statistically processed by analysis of variance and subjected to correlation analysis (n = 12 ). In LAV fertilized treatment the highest average dry matter yield of herbage was recorded (by 9% on average). It was manifested significan tly particularly in the period with lower level of rainfall and higher level of temperatures (Fig. 1). In LV fertilized treatment significan tly lower nitrate content was recorded (by 80% on average), crude prot ein and nitrogen-energy quotient, particularly in the third year with sufficiency of rainfall and optimal temperatures (Fig. 2). No statisti cally significant differences were obtained on average for the whole t rial in most indicators of nutritive value of the herbage. In fibre si gnificant negative correlation to N content (r = -0.7863) was determin ed. All investigated parameters were affected by meteorological condit ions and stage during harvest. In LV fertilized treatment much lower P content in herbage was observed (Fig. 3). This was conditioned obviou sly by low diffusion of phosphate compared with nitrate. P content was dependent on amount of rainfall (I = 0.5531) and hydrothermic coeffic ient (HTK) (r = 0.6766). In the same treatment insignificantly lowest K content in herbage was recorded, and on the contrary, there was sign ificantly highest content of Ca and Na, and increased Mg content. Sign ificant negative correlation between K and Ca (r = 0.8011), K and Na ( r = 0.7638), K and Mg (r = 0.3257) was found. Significant differences were particularly in the second and third years when the level of exch angeable K in soil and K concentration in soil solution were reduced ( Tuma, Matula, 1993) the ratio of exchangeable K and Mg was balanced. U nder these conditions the competitive effect of other cations on K int ake could be manifested. K content in herbage was further influenced m ainly by rainfall (r = 0.3947) and HTK (r = 0.5263) as well as by grow th stage (ageing of the stand resulted in reduced K content in herbage ). As it is evident from Fig. 5, easily available Ca content in LV (20 % Ca) significantly was displayed in the growth of its content in herb age (on average by 9%). Highly positive correlation between Ca and Mg content (r = 0.7143) was recorded, and between Ca and Na (r = 0.7021) in herbage as well. Ca content in herbage was in positive correlation with average temperature (r = 0.6474) and in negative correlation with HTK (r = 0.4374). Differences in Mg content were insignificant on ave rage (Fig. 6). Mg content was much affected by temperature (r = 0.7852 ), therefore usually first cuts showed lowest Mg content. Na content i n herbage in LV fertilized treatment exceeded highly significantly (by 57% on average) other treatments (Fig. 7). Negative correlation was f ound between Na content and amount of rainfall (r = 0.3904) and HTK (I = -0.3616). It was confirmed that ageing of herbage resulted in reduc tion of Na content (r = -0.3048 to the number of days of growth recove ry). Interaction between cations reflected in the values of ratio of e quivalents K/Ca + Mg + Na (Fig. 8), Ca/P (Fig. 9) as well as N/K + Ca + Mg + Na (Fig. 10).