THE EFFECT OF LONG-TERM FERTILIZING AND LIMING ON SOIL-PH AND CROP YIELDS

Ca content in soil (Mehlich II), variations of soil pH values and crop yields in 1990 to 1997 were evaluated at five sites with long-term st ationary plant nutrition trials. Tab. I shows the site characteristics . Differentiated application rates in the particular variants and iden tical crop rotations were used at all sites: at Lipa and Libejovice si nce 1974, at Chrastava since 1977, and at Stankov and Svitavy since 19 80. These crops were grown at all sites in the period of evaluation: o ats with clover underseeding in 1990, meadow clover in 1991, winter wh eat in 1992, potatoes in 1993, winter wheat in 1994, spring barley in 1995, potatoes in 1996, spring barley in 1997. Four fertilization vari ants were evaluated: var. 1 unfertilized, var. 2 farmyard manure + lim ing, var. 3 farmyard manure, NPK + liming, var. 4 farmyard manure + NP K. Farmyard manure was applied at a rate of 40 t/ha in fall 1992 and 1 995, liming in form of limestone application was carried out the basis of soil analysis in fall 1991 and 1994 at rates of 2.8 and 1.6 t at C hrastava, 0.7 and 0.8 t at Libejovice, 2.0 and 0.8 t at Lipa, 1.2 and 0.8 t at Stankov and 2.5 and 0.8 tat Svitavy: An annual dose of phosph orus was 52.3 kg P and that of potassium 132.8 kg K (per ha). Nitrogen application rates for the separate crops (per ha): 100 kg to oats wit h underseeding, 140 kg to winter wheat, 160 kg to potatoes, and 92 kg to spring barley after wheat and 80 kg to spring barley after potatoes . A decrease in soil pH values and a reduction in Ca content in soil w ere recorded in variants without liming. Substantially higher variatio ns were determined for variants with fertilizer applications. Regular liming (var. 2 and 3) maintained soil pH values around 6, and higher C a concentrations in soil. A high positive correlation (r = 0.94) was c alculated for the relation between pH value and Ca content in soil. Th e yield on unfertilized plots over eight years in total was 31.4 to 39 .9 cereal units per ha at the separate sites. Yields were increased by applications of farmyard manure and liming (var. 2) against unfertili zed variant by 1.6 to 15.4% subject to the site, an average increase a t all sites was 10.9%. A yield increase on plots with farmyard manure and fertilizer applications (var. 4) was 47.6 to 83.7% against unferti lized variant, and 59.6% on average for all sites. The variant with fa rmyard manure and fertilizer applications and liming (var. 3) gave the highest yields, an increase against unfertilized variant was 59.6 to 102.8%, an average increase for all sites being 74.1%. Yields were inc reased by 2.0 to 17.8% by liming only (comparison of var. 3 and 4), an average increase for all sites was 9.1%. In order to maintain the req uired soil fertility and yield stability, applications of farmyard man ure, fertilizers and liming are necessary at all sites.