Menetelmä laidunnurmen keskimääräistä kasvua kuvaavan käyrän laatimiseksi

Authors

• Tauno Laine Laidunkoeasema, Mouhijärvi

DOI: https://doi.org/10.23986/afsci.71340

Abstract

The paper presents a method of drawing a curve describing the average growth of grass in pastures on the basis of pasture experiments extending over several years. The starting point is Rappe’s (5) method of drawing a growth curve for one growth period. Where the experimental plots are to be mown, the daily growth of the grass is first calculated for each experimental year separately, as Rappe has described (the yield divided by the number of days passed since the previous mowing). The growth values for the periods between mowings are then put down in the time-table given in Table 2 (p. 187), each year on a different line. For instance, in the year 1951 the dates of mowing were June 20th, July 25th, and September 11th, and the amounts of daily growth 14, 26 and 2 kg per ha of dry matter. The midpoint of each period and the average of the annual growth values for the same period are giwen beneath the table. Thus the midpoint of the period June 10th—June 20th is June 15thand the average of the annual growth values for this period (14 +34 + 36) : 3 = 28 kg per ha of dry matter per day. The values for average growth calculated in this way are then marked in a system of co-ordinates where the time from spring till autumn is on the x axis and the amount of growth on the y axis. The points are joined by straight lines, and the final growth curve is drawn along the line indicated by the midpoints of the lines. This method of drawing the curve aims at modifying the irregularities caused by occasional factors. This method was used in Figure 2 (p. 187), which also gives levels showing the average growth for different periods. The curve of average growth is drawn separately for each member of the experiment, and finally added to the same system of co-ordinates in the way shown in Figure 3 (p. 190). As the space limited by the curve of average growth and the x axis represents the total yield of the growth period, the curve indicates both the amount of yield and the average changes in growth occurring during the growth period. In the case reported, growth is assumed to have begun at the beginning of May in the different years. The curve of average growth for experimental plots grazed with livestock is drawn in a similar way, except that the time representing the periods between different mowings is the period needed for grazing the pasture once and the number of fodder units received by the animals during this period. If, at any time, the animals were not grazing in the pasture, the interval was included in the next period of grazing. The growth period is supposed to have begun when the animals are put out to grass in spring. Figure 4 (p. 191) gives the curves of average growth for an experimental plot grazed with sheep.