A SURVEY OF FORAGE QUALITY IN RELATION TO FLORISTIC COMPOSITION ON LOWLANDS PASTURES IN NW OF GALICIA (NW SPAIN) - l.R. Calvo^[41], A. Gonzalez^[42] and M.I. Fraga^[43]

SUMMARY

A survey of forage quality was carried out in 41 Galician pastures, using the FLORASYS computer program. In 16 pastures the forage had reached a 'high' quality level; 19 were considered of 'medium' quality and six were of 'low' quality. The percentage of high and medium levels was nearly the same for permanent and sown pastures.

The number of sown and native species was the main factor determining the quality forage. Six grasses species (Lolium multiflorum, Dactylis glomerata, Lolium perenne, Agrostis stolonifera, Agrostis capillaris and Holcus lanatus) and four legume species (Trifolium repens, Trifolium pratense, Lotus corniculatus and Ornithopus compressus) produce high quality forages, if they are abundant in the sward.

Keywords: Floristic composition, forage quality, pasture

INTRODUCTION

It is obvious that forage quality is closely related to the botanical composition of swards. In order to obtain good quality forage, this composition can be controlled by management practices; mainly by fertilization and sowing. According to Snaydon (1987) for temperate pastures, control by sowing good quality cultivars in Galicia is only partially successful, because after sowing many indigenous species tend to invade the sward, competing with sown cultivars for available resources. Usually, native species are more competitive than cultivars and as a result the proportion of sown species declines and the botanical composition of pastures changes with sward age.

The forage quality of sown grasslands is usually considered higher than for permanent pastures, but evidence for this in Galicia is sparse (Mosquera and Gonzalez, 1995). This paper introduces a new approach to quickly evaluating the quality of forage on the basis of floristic composition and species frequencies of the pasture.

MATERIAL AND METHODS

This survey was carried out in six councils of the Coruña province (Moeche, Neda, Capela,Valdoviño, Ferrol and Abegondo). A total of 41 pasture plots were studied (25 permanent pastures and 16 sown grasslands). Floral inventories, with visual estimation of frequencies of all recorded species (number of individuals per m² in the plot) were drawn-up in 1997. The forage quality, as well as forage diagrams, were analysed on the basis of species composition, frequencies of every recorded species in the plot and their forage value, using the Florasys computer program. Table 1 shows the forage values given to the major forage species, according to Plantureux and Bonischot (1993), in Florasys program.

RESULTS

Table 2 summarizes the results. Within permanent pastures nine had reached a high quality forage level, with quality values (Qv) higher than 50; 11 were considered as medium quality (50>Qv>40) and five were of low quality (Qv<40). In sown grasslands the results were quite similar, seven had reached high quality, eight medium quality and only one, located in Moeche, was of low quality.

When comparing plots on the basis of their geographical location, there was great heterogeneity among and within areas. Capela was the most variable area; in this council half of the permanent pastures surveyed were of high quality and the other half were of low quality (no intermediate levels were observed). In the other five areas, as well as for permanent pastures as sown grasslands, the number of plots with high quality forage was nearly the same as that of medium quality.

Forage composition (Table 2) demonstrated how permanent and sown pastures can reach similar quality levels. Although in leys, sown cultivars of Lolium multiflorum, Dactylis glomerata and Trifolium repens have high or very high quality levels, they are abundant for only a short time after sowing and their percentage in the sward decreases as the native species invade the pasture. These invaders cause a decrease in the quality to medium levels, especially if the sward is more than three years old. Conversely, if indigenous Dactylis glomerata, Trifolium repens, Lolium perenne, Agrostis stolonifera, Agrostis capillaris and Holcus lanatus are abundant in permanent pastures, these can reach high quality levels.

It is obvious that a low number of sown and native species is the main reason for quality forage. Six grasses species (Lolium multiflorum, Dactylis glomerata, Lolium perenne, Agrostis stolonifera, Agrostis capillaris and Holcus lanatus) and four legume species (Trifolium repens, Trifolium pratense, Lotus corniculatus and Ornithopus compressus) produce high quality forages, if they are abundant in the sward. Species belonging to other families played an unimportant role in good quality forages and they are generally considered undesirable species.

Table 1. Quality and productivity levels of the major forage species.

Q: Quality, P: Productivity VG: Very good, G: Good, QG: Quite good, M: Mediocre, VP:Very productive, P:Productive

Table 2. Percentages of the main forage components and forage quality values.

VGg: Very good grasses, Gg: Good grasses, QGg: Quite good grasses, Mg: Mediocre grasses, VGl: Very good legumes, Gl: Good legumes, QGl: Quite good legumes, Ml: Mediocre legumes, OF: Other forage species, OM: Other mediocre species, ONF: Other no forage species, QV: Quality forage value

REFERENCES

Mosquera, R. & Gonzalez, A. 1995. Estudio de la composición botánica en sistemas lecheros sometidos a distinta carga. Actas Congreso Sociedad. Española. Malherbología: 73-76.

Plantureux, S. & Bonischot, R. 1993. Florasys: Système informatique de gestion et d'aide à l'interprétation des relevés floristiques.

Snaydon, R.W. 1987. The botanical composition of pastures. In “Ecosystems of the world” 17B:81-87. Ed. R.W. Snaydon. Elsevier Publishers.