Understanding the relationship between dry matter yield production and forage quality throughout the growing season will help to optimize the cutting intervals between harvests in different Alfalfa (Medicago sativa L.) varieties. An experiment was conducted to assess the effects of harvest frequency on forage yield and quality of 2 improved cultivars (ILRI-6984 and var. DzF-552) of alfalfa (Medicago sativa L.) in Western Dembia district over 20 months during 2017 and 2018. Four harvest frequencies (every 30, 40, 50 and 60 days) were compared in a randomized complete block design (RCBD) with 4 replications. The experiment was laid down in a randomized complete block design (RCBD) in factorial arrangement with four replications. To assess their production potential plant height (cm), number of branches per plant, fresh biomass yield (t ha−1) and dry matter yield (t ha−1) of the forge and its nutrient content were recorded. The data collected was subjected to analysis of variance (ANOVA) by using the general linear model (GLM) procedure in Statistical Analysis System (SAS) (2003) version 9.1.
The results revealed that highest forage dry matter yield was recorded for variety ILRI-6984 harvested every 40 days (26.8 t DM ha−1) and for var. DzF-552 when harvested every 60 days (24.1 t DM ha−1) (P<0.001). While crude protein concentration tended to decline as age at harvest increased, there was little consistency in the pattern. Crude protein yields were also inconsistent across treatments but ILRI-6984 harvested every 40 days produced the highest yields (6.5 t ha−1) (P<0.001).
These preliminary findings need to be confirmed under field conditions on a large scale along with longer-term studies to examine the longevity of the stands at these harvest frequencies. Irregular harvesting based on stage of maturity should be compared with fixed inter-harvest intervals.