Continuous Forage Production by Means of Rotating Cool- and Warm-Season Grasses : I. Effects of oats and Italian ryegrass on the growth and yield of undersown Setaria

Abstract

An experiment was conducted to investigate the use of preceding oats or Italian ryegrass with undersown Setaria (Setaria anceps cv. Kazungula) herbage. It consisted of five combinations of the crops, that was three pure plots of Setaria (S-pure), oats (O-pure), and Italian rygrass (I-pure), and two undersowing plots of Setaria with oats (O-S) and that with Italian ryegrass (I-S). Sowings and cuttings were practiced as shown in Fig.1. Results were summarized as follows, 1) Germination percentage of Setaria was reduced, but not significantly, when accompanied with the preceding crops. About two months later, Setaria establishment percentage among aftermath of the accompanied crop showed significant reduction owing to the low light intensity (Table 1). 2) Earlier dry matter yield of preceding crops was added in undersowing plots, but the differences in the total yield among those and S-pure were not significant as shown in Fig.2. Higher Setaria component was resulted in O-S than in I-S plot. 3) At the third cutting (2 Aug.), when Setaria growth alternated with the aftermath of preceding crops, both undersowing plots yielded only about a quarter of S-pure, reflecting heavy competition for light. 4) Growth analysis of Setaria plant at the alternation period was shown in Fig.3. At the 25th day from sowing, Setaria plant weight under oats and Italian ryegrass was retarded to 1/9 and 1/90 respectively, comparing to that of the pure plot ; this shows delay of about 11 and 33 days growth respectively. Relative growth rate per day of Setaria showed the highest value of 0.078 in case of with oats, which supposed to be better combination than with Italian ryegrass.