THE DATE OF CUT ON THE PRODUCTION, GROWTH RATE AND BOTANICAL COMPOSITION OF GRASS-LEGUME ASSOCIATIONS

Abstract

Background. The association of legumes with grasses improves the quality of the diet as well as the protein value, increases productivity, allows savings in nitrogen fertilizer and maintains the proportion of the botanical components of the meadow. The cutting date affects the productive behavior of the forages species in temperate, arid and semi-arid climate zones. Therefore, it is important to continue evaluating established grassland with legumes associated with grasses to generate information that will serve producers and increase the economic profitability of livestock activities. Objective. The objective of the present study was to evaluate the cutting date on dry matter production (PMD), growth rate (RG), botanical composition (BC), as well as relationships between RG and PMD and BC and PMD. Hypothesis. It is evident that the cutting date modifies the PMD, RG, as well as the relationship between RG and BC with PMD, but has no influence on BC. Methodology. Meadows irrigated with Trifolium alexandrinum L. associated Lolium multiflorum Lam. of a proportion of 40:60 sowing seeds, respectively subject to eight cutting dates (treatments): T1 = 90 to 97 days elapsed between the sowing date and the first cut (DTS-PC), T2: 97 to 104 DTS-PC, T3: 104 to 111 DTS-PC, T4: 111 to 118 DTS-PC, T5: 118 to 125 DTS-PC, T6: 125 to 132 DTS-PC, T7: 132 to 139 DTS-PC and T8: 139 to 146 DTS-PC, under a randomized complete blocks design with four replicates. The trend of the factor under study (cutoff date) on the response variables was determined using orthogonal polynomials. Results. The DTS-PC caused a linear positive effect (P <0.001) of the evaluated species on the PMD and RG, observing that increasing the DTS-PC increased the PMD. (P = 0.0001). In contrast, no significant differences (P> 0.05) were observed in the BC. Regardless of the DTS-PC, the legume as T. alexandrinum contributed 64 % of the biomass, these percentages were determined dividing the PMD of T. alexandrinum by the PMD of L. multiflorum added with that of dead material and weeds. There was an effect of the DTS-PC on the relationship of RG:PMD (linear effect, P <0.01), while for the ratio relationships BC:PMD only a linear decrease was presented (P <0.01) at increasing the DTS-PC.  Implications. The results of the present study contribute to knowing the productive parameters of a grass established with legume-grass in temperate, arid and semi-arid climate zones to improve the production of meat and milk. Conclusions. The elevation of the cutting date increased the PMD, but has an inverse effect for the relationships BC:PMD, as well as RG:PMD of each species.  The highest RG was found at 97-104 DTS-PC for the evaluated species and dead material.