Effects of phosphorous and potassium fertilization on spring weed invasion in alfalfa meadows

摘要

A field trial was conducted from 2005 to 2007 in north-eastern Italy to study the influence of phosphorous and potassium fertilization on the performance of alfalfa meadows. Alfalfa (Medicago sativa L.) cv. Delta was seeded on 30 March 2005 in a silty-loamy soil. Nine treatments deriving from the factorial combination of three rates of phosphorous (0, 100 and 200 kg ha~(-1) year~(-1) of P_20_5) and three rates of potassium (0, 300 and 600 kg ha~(-1) year~(-1) of K_20) were compared in a randomized complete block design. In order to study the effects of phosphorous and potassium fertilization on spring weed invasion, root dry weight (g plant-1), root diameter (mm) and stand density (plant m~ 2) at the last harvest of 2007, and the weed cover (%) at spring 2007, were then examined. Weed cover was not influenced by phosphorous rates, but decreased with increasing potassium rates. This result was likely due to the increase of plant vigor in consequence of potassium application as revealed by the increase of root dry weight, root diameter and individual plant yield.