Growth and yield responses of carrot (Daucus carota L.) to different levels of oil palm refuse bunch ash in an ultisols environment

Abstract

A field experiment was conducted from July – October, 2015 and 2016 at the Experimental Farm of the Faculty of Agriculture, University of Benin, Benin City, Nigeria, to determine the effect of oil palm bunch ash on the growth and yield of carrot (Daucus carota L.) and the soil post-harvest chemical properties. The study involved the application of oil palm refuse bunch ash at six (6) levels (0, 2, 4, 6, 8 and 10 t ha^-1). The treatments were arranged in a randomized complete block design (RCBD) with four replications. Data were collected on growth variables (number of leaves and height of plant) at two (2) weeks interval. After harvest, data were collected on root length, root girth, leaf weight, root weight, and root yield. The results of the trial showed that non-oil palm refuse bunch ash (non-OPRBA) plants had shorter plants and fewer number of leaves than OPRBA treated plants. At harvest, weight of aerial portion, root:shoot and root yield were highest with plants treated with PORBA at 10 t ha^-1. Postharvest soil chemical properties indicated PORB ash enriched the soil with organic carbon, total N, available P and exchangeable cations (Ca, K, Mg and Na). PORBA application rate of 10 t ha^-1 is hereby recommended for carrot growers in the humid ultisols environment.