Plant Mass and Yield of Broccoli as Affected by Soil Moisture

Abstract

The effect of water supply on total mass and yield of broccoli (Brassica oleracea L. var. italica, `Emperor') was examined in an experiment carried out in a microplot field installation on three soil types: Gleyic Cambisol (sand) and Eutric Fluvisol (flood-plain loam) in spring and fall and on a Haplic Phaeosem (loessal loam) in fall. Soil moisture levels were established by irrigation under the following replacement protocols: 14 mm whenever the limit of 75% vol of the available soil water (ASW), 14 and 28 mm whenever the limit of 55% vol of ASW, and 14, 28, and 42 mm whenever the limit of 35% vol of ASW were reached. The highest total plant mass was achieved by irrigation at 75% vol of ASW on the sandy soil in spring cultivation, and at 55% vol of ASW (in doses of 28 mm) on the flood-plain loam in fall cultivation. The highest marketable yield (head mass) was obtained on the sandy soil at 55% vol of ASW (in doses of 14 mm) for both spring and fall production. The total plant mass and head mass was only significantly affected by reduced soil moisture at 35% vol of ASW in spring. At 75% vol of ASW, irrigation with 14 mm always resulted in reduced headmass. In fall, yield was not affected by soil moisture depletion or soil type. For the production of broccoli, it is recommended that irrigation be started when soil moisture falls below 55% vol of ASW, followed by a water application rates of either 14 or 28 mm.