nitrogen source
... that winemakers used to add urea to grape must as a nitrogen source for wine yeast?
... that winemakers used to add <a href="./Urea" id="mwDDU" rel="mw:WikiLink" title="Urea">urea</a> to <a href="./Must" id="mwDDY" rel="mw:WikiLink" title="Must">grape must</a> as a <b id="mwDDc"><a class="mw-redirect" href="./Nitrogen_source_(wine)" id="mwDDg" rel="mw:WikiLink" title="Nitrogen source (wine)">nitrogen source</a></b> for <a class="mw-redirect" href="./Wine_yeast" id="mwDDk" rel="mw:WikiLink" title="Wine yeast">wine yeast</a>?