Tärkeimpien kasvutekijöiden ja käytetyn viljelytekniikan suhteet nurmen kasvurytmiin ja sadonmuodostukseen

Authors

• Seppo Pulli Helsingin yliopisto, kasvinviljelytieteen laitos

DOI: https://doi.org/10.23986/afsci.72034

Abstract

The relationships of the growth rhythm and yield formation pattern of a clover-grass stand and a pure grass stand to the growth factors and management techniques were studied at Viikki in 1973—78. The objectives concerning management were the first cutting date and cutting frequency of a clover-grass stand and the number of cuttings, N-fertilization and seeding rate of a pure fescue stand. The most important growth factors in spring dry matter production were temperature sum (∑ > 0° C), solar radiation sum and N-fertilization. In summer growth the most important variables in the regression model were factors relating to precipitation. In the fall DM growth the most determining factors were the growth activity in the previous cut, N-fertilization and the amount of light. The spring growth was characterized by the distinct changes among all components of the yield studied. The shape of all spring growth models was strongly sigmoidal. As the growing season progressed DM yield or quality characteristics of the yield as a function of time or temperature sum in degree days approached the quadratic or linear relationships. The energy value of a clover-grass stand varied between the range of 4.274— 4.633 kcal gr-1. The photosynthetic efficiency of the stand among different cutting systems in 1974—75 was between 0.31—1.12 % determined from the total radiation per unit area. Deficiency of water was the most important factor causing variation in assimilation efficiency. Cutting frequency was the most important factor influencing the yield distribution of the season, the relationships among plant species and the formation of the total yields. Less important management factor was the first cutting date. N fertilization increased DM yields significantly in all cutting systems. The increase in use of nitrogen from 130 to 260 kg N ha-1 raised the protein content of the yield by 4.2 % units and the protein yield by 485 kg ha-1. The maximum DM yields in the seeding year and during the following three production years were obtained with seeding rates of 60, 30, 15 and 7.5 kg ha-1 respectively. The quality of the yield was very little influenced by growing density.