Comparison of Dry Matter Production in Forage Grass Species

Abstract

Dry matter production was compared between the two groups of four grass species which differ in photosynthetic capacity and optimum temperature for growth. The species were oats, Avena sativa L. Italian rye grass, Lolium multiflorum, (species of low photosynthetic capacity and low optimum temparature), barnyard grass, Panicum Crus-galli var. echinata and sorgo, Sorghum vulgare (species of high photosynthetic capacity and high optimum temperature). Experiments were carried out from summer to autumn in 1966 for 74 days with two sowing densities and for spring in 1967 for 51 days with one sowing density. The results of high density plot only were described. Panicum and Sorghum produced much higher dry matter and had higher crop growth rate (CGR) then Avena and Lolium (Fig. 1 and 4) in the experiment in 1966. It was shown that the former species had the higher leaf area indeces (LAI) in an early growth stage (Fig. 2) and had the higher net assimilation rate (NAR) even in the growth stage of high LAI than the latter species (Fig. 3). The comparison was also made in dry weight ratio of nonphotosynthetic system to photosynthetic system and specific leaf area, but no consistent result with dry matter production was obtained (Table 3). In the experiment in 1967, which was carried out for a period of lower temperature, longer day length and for younger stage, than the one of 1966, sorghum showed higher CGR, higher relative growth rate, higher relative leaf growth rate and higher NAR than Lolium (Table 5). It was noticed that NAR was one of the most important factor for dry matter production in the young stage with low LAI. From these results, the significance of NAR or photosynthetic capacity per unit leaf area (P) in dry matter production was discussed. It was concluded that not only leaf area but NAR or P were important and that the high dry matter production of forage grasses could be achieved with the species which possess both the ability of high NAR or P and of high growth rate in leaf area simultaneously.