The effect of fertilization and soil cultivation on the yield of maize (Zea mays L.)

The effect of crop production factors on the maize yield was studied on a chernozem soil with lime deposits at the Latokep Experimental Farm of the Department of Land Use of the Debrecen Agricultural University between 1989 and 1994. A multifactorial long-term experiment made it possible to evaluate the effects and interactions of fertilization and soil cultivation. Soil cultivation can only be considered to be up-to-date and adaptable if it is adjusted both to soil status and to farming conditions. The method, tool and depth of cultivation must be chosen to suit the physical state of the soil. A consideration of the moisture content of the soil reduces damage to the soil structure. The experimental results prove that on a chernozem soil, provided precipitation supplies are at least average, winter ploughing, even without fertilization or with low fertilizer rates, causes a substantial increase in the maize yield by making the soil nutrients available to the plant. The extra yield achieved with winter ploughing without fertilization was 1.4-2.3 t/ha compared to the unploughed variant. In fertilized treatments the yield increase was greater, averaging 2.8-3.3 t/ha. Over a six-year average, the yields were 0.6 t/ha lower after spring ploughing than after winter ploughing. In dry years the yield difference was somewhat smaller, but under favourable rainfall conditions maize grown after spring ploughing yielded 1.0-1.4 t/ha less than after winter ploughing. Fertilization was able to compensate in part, but not entirely, for other unfavourable agrotechnical effects. Without ploughing the extra yield due to fertilization was 2.8 t/ha in dry years and 3.8 t/ha under more favourable rainfall conditions. After winter ploughing the difference between the years was smaller (0.6 t/ha), with an extra yield of 3.1 t/ha in dry years and 3.7 t/ha after average rainfall. The yield-increasing effect of fertilization, averaged over the six years examined, differed in the three soil cultivation variants. Linear and quadratic terms were significant in the fertilizer effect, so the relationship can be described well using an optimum curve. The breakdown of the interaction between fertilization and soil cultivation using orthogonal polynomes indicates that in the linear phase, representing initial low fertilizer rates, there is no substantial difference of the three types of soil cultivation.