Nitrogen & harvest date

The effect of nitrogen application and primary growth harvest date on the yield and quality of multi-species swards for silage production

This experiment is examining the effects of various rates of N fertiliser on a range of herbage treatments managed for the production of silage. Experimental plots are arranged in four replicate blocks, each with a split plot design. Herbage treatments include monocultures of perennial ryegrass (Loilium perenne), Italian ryegrass (Lolium multiflorum), timothy (Phleum pratense) and red clover (Trifolium pratense) as well as binary mixtures of red clover with each of these single grass species. There are also more complex mixtures containing two grasses (perennial ryegrass and timothy), two legumes (red and white clover) and two herbs, chicory (Cichorium intybus) and ribwort plantain (Plantago lancelota). Fertiliser nitrogen application rates range from 0-360 kg N/ha per annum. Each herbage x fertiliser N combination has replicate plots with primary growth harvests taking place in mid-May, late May or early June. Subsequent regrowths are being assessed throughout the year to allow the full annual production of herbage be quantified.

Prior to each harvest, a full botanical assessment is carried out in which species abundance and plant growth stage are determined. Herbage is cut using a Haldrup plot harvester before being chopped with a forage harvester. A sample of fresh herbage is taken from all plots to determine dry matter yield and chemical composition. Select treatments from throughout the season are ensiled in laboratory silos to determine the effects of treatment on conservation characteristics and silage quality.