Growth Analysis of Irrigated ‘Tifton 85’ and Jiggs Bermudagrasses as Affected by Harvest Management

Abstract

Growth analysis of forage crops allows integration of photosynthesis, respiration, and allocation of photosynthate from estimates of physiological and morphological indices. These measurements help explain differences in growth potential between plants across seasons and in response to harvest management. The objective was to describe and explain patterns of growth of ‘Tifton 85’ (Cynodon spp.) and Jiggs [C. dactylon (L.) Pers.] bermudagrasses to three harvest frequencies (14, 28, and 42 d) during 2 yr. Grasses showed different growth patterns during the cool and warm seasons. Crop growth rate (CGR) was similar during the warm season (69 kg ha–1 d–1), but Jiggs had greater relative growth rate (RGR) and lesser stubble mass and residual leaf mass. Jiggs had greater net assimilation rate (NAR) than Tifton 85 during the warm (14.2 vs. 11.4 kg dry matter [DM] m–2 d–1, respectively) and cool seasons (6.9 vs. 2.5 kg DM m–2 d–1, respectively). Tifton 85 partitioned more biomass to leaf than Jiggs (leaf weight ratio [LWR] of 0.35 vs. 0.28 kg kg–1). The 14‐d harvest frequency reduced CGR, RGR, and NAR of both grasses. Small changes in RGR occurred beyond 28 d of regrowth, but leaf area ratio (LAR) and LWR decreased, suggesting that grasses should be harvested ∼ every 28 d during the warm season. Longer regrowth periods during the cool season increased both CGR and RGR. Harvest management affects differently the growth and morphological components of Jiggs and Tifton 85 in this environment.