Grazing and nitrogen on the growth of roots in the mixture of oat and ryegrass

Abstract

This study evaluated the effect of grazing and its absence, and the nitrogen on the morphology of roots of black oat (Avena strigosa Schreb.) mixed with Italian ryegrass (Lolium multiflorum Lam.). The experimental design was a randomized block design in split-split, the main portion was study the effects of grazing and its absence, in the subplots the nitrogen doses of 75 and 150 kg ha-1 and in the sub-subplots were at sampling period. There was used the cylinder method to collect the root, being measured the length, surface area, mean diameter and volume by image analysis system Win / MacRizho (4.1c). Determined the dry mass of roots and shoot, and estimated the density of the root tissue and shoot:root ratio. From these results we determined the rate of root growth relative (RGR), relative root expansion rate (RRER) and rate of accumulation of dry matter daily (RADM). In the first period, was higher RGR, RRER, the second period there was a reduction of the same, probably due to the period of drought and plant senescence. There was also reduced due to grazing RADM. With grazing, the length, surface area, mean diameter and root volume were higher, indicating that there was greater root growth of plants grazed compared to ungrazed. The systems studied had no effect on the dry weight of roots. There were found greater specific mass and shot:root ratio in the system without grazing. There was no significant difference between the nitrogen studied. At mixed of black oat and ryegrass, the grazing and nitrogen dose until 150 kg ha-1 little affect root growth. The nitrogen dose changed a little the growth rates and expansion of the roots. On the other hand, the grazing favored the length, area, volume and root diameter.