Abstract
The fitness of equations predicting nutrient yield of corn silage from the ear corn and stover yield per unit area was investigated using 6 early maturing varieties 3 medium maturing varieties and 4 late maturing varieties cultivated in Tokachi district, Hokkaido, during the years from 1974 to 1980. The results are summarized as follows. (1) The yearly weather as judged by the crop, was normal in 1974, 1977 and 1979, good in 1975, 1978, and poor in 1976, 1980. Each year, the crops were harvested between 24 and 26 of September. Maturity stages of the crops at that time differed widely depending on the years and varieties. Generally, they fell between early yellow dent to overripe stage with the early maturing varieties, late dough and yellow dent with the medium ones, and early milk and early dent stages with the late ones. (2) The yield of dry ear corn ranged from 228 to 920kg, and dry stover yield from 365 to 1025kg per 10 are. (3) The ranges of dry matter (DM) recovery of silages, total digestible nutrient (TDN) contents, digestible energy (DE) contents were ; 87.4-96.1% for DM recovery, 60.7-73.7% for TDN, 2.72-3.29kcal/g・DM for DE contents, respectively, and the yield of TDN and DE of silages ranged ; 611-1123kg for TDN, 2911-4882 therm for DE per 10 are. (4) A significant correlation was recognized between the yield of TDN or DE (Y) and that of dry ear corn (X_1) and dry stover (X_2). However, the TDN yield predicted by the so-called Shintoku's equation tended to give significantly higher values than those obtained by presnt measurements. The resulting over-estimates seemed to be due to the fact that the Shintoku's prediction system neglects the dry matter loss which occurs during the process of silage making, and also it is likly to over-estimate the nutritive value of stover especially in late maturities. From the analysis of our experimental results, the authors are inclined to suggest the substitution of coefficients in the prediction equation, which will give better approximation to the actual values of nutrient yield. The improved equations thus derived are as following. TDN yield Y=0.8×dry ear corn weight (X_1)+0.5×dry stover weight (X_2) DE yield Y=3.3×dry ear corn weight (X_1)+2.4×dry stover weight (X_2).
