Comparison of fertigation with broadcast applications of urea-N on levels of available soil nutrients and on growth and yield of trickle-irrigated peppers

Abstract

Extensive soil acidification, caused by nitrification, occurred below the trickle emitters in the fertigated and broadcast/fertigated treatments. Acidification also occurred in the surface of the broadcast treatment and was greater at the higher rate of N addition. Soil acidification resulted in large increases in levels of exchangeable Al and reductions in concentrations of exchangeable Ca, Mg and K. Levels of EDTA-extractable Fe, Mn and Zn were also increased. Vegetative growth and yields of peppers showed similar trends, being greatest at the low rate of N applied as fertigation or as a combination of broadcast plus fertigation. In these treatments, growth was reduced at the high rate of N due to Al toxicity induced by soil acidity below the emitters. Growth in the broadcast-N treatment was inferior to that in the fertigation treatments at the low N rate, but was similar at the high N rate. It was concluded that methods of ameliorating and/or preventing soil acidification below trickle emitters need to be developed if fertigation with acidifying nitrogenous fertilisers is to be practiced routinely.