Liming and calcium cyanamid for clubroot control in cauliflower

Clubroot of crucifers is a major problem worldwide. Liming has been used as a control measure since the early 19(th) century. Liming must be done so as to raise soil pH to a suitable level as quickly as possible. For this purpose, relatively massive applications may be used sometimes with faster acting lime types than agricultural lime. However, the single use of lime often falls short of a satisfactory control on the disease. This study compared the effects of six control strategies involving calcium cyanamid, a nitrogen fertilizer known as having disease control properties, together with lime treatments for a cauliflower crop. Application of calcitic I lime [CaCO3] was made in fall, just after ploughing. Two rates were applied (5 t.ha(-1) and 25 t.ha(-1)). In spring, calcium cyanamid (500 kg.ha(-1) preplant or post-planting) and hydrated lime [Ca(OH)(2)] (1.5 t.ha(-1) banded at planting) treatments were applied on top of the different calcitic lime treatments. Soil pH was monitored throughout the growing season. Even if the control plot received 5 t.ha(-1) of calcitic lime, the yield losses caused by clubroot were considerable with a marketable yield of only 1.2 t.ha(-1). The best control strategy, with a marketable yield of 18.8 t.ha(-1), was calcium cyanamid applied pre-plant on top of 25 t.ha(-1) of calcitic lime. Hydrated lime banded at planting in combination with 5 t.ha(-1) of calcitic lime also showed good results, with a marketable yield of 13.1 t.ha(-1). There was a synergetic effect among treatments. Calcitic lime application alone, even at 25 t.ha(-1), did not provide satisfactory clubroot control.