Yields of field crops in conditions of mountain region

in exact field trials in two different crop rotations the effect of fertilization by industrial fertilizers and manure was studied as affected the yields and the stability of yields of field crops in mountain production type, Experimental site is situated at 670 m above sea level. Average annual air temperature is 5.8 degrees C, with average annual sum of precipitation 1020 mm. Crop rotations: A) red clover, winter rye, root crop, oat with underseeding: B) red clover, triticale, root crop, spring barley with underseeding. The following three variants of fertilization were selected for each crop rotation: 1, fertilization by industrial fertilizers (used doses of nutrients see Tab. I); 2, fertilization by industrial fertilizers as variant 1 and 30 t.ha(-1) of manure to root crop; 3, manuring in a dose of 60 t.ha(-1) to root crop and 30 t.ha(-1) winter cereal. The greatest differences in the yield of main product as well as in the total production expressed in cereal units were found between variants fertilized in combined way (manure and fertilizers) and variants fertilized only by manure. Red clover alone in the systems of crop rotations did not respond to fertilization, slightly increased hay yields gave in the manured system (3). The other variants only manured (winter and spring cereals, root crops) showed a decrease of yields by 20 to 34% compared with average, Yield stability evaluated Tor three experimental years (1995, 1996, 1997) was highest in red clover and spring cereals, lower in root crops. It has been showed that replacement of nitrogen fertilizers by manures cannot stabilize yields and prevent contamination of waters, Results confirm that classical system of organo-mineral fertilization was not significantly better than sole fertilization by fertilizers, if perennial leguminose is in the system. Fertilization by organic fertilizers alone in all years showed (except red clover) highly significant decrease of crop yield and productivity of crop rotations. Optimization of production in marginal regions is possible above all by stabilization of crop rotations in representation of perennial forage crops and balanced manuring and fertilizing.