CONTROL OF MANGANESE DEFICIENCY IN-FIELD PEAS GROWN FOR SEED OR HUMANCONSUMPTION

The effect of foliar applications of different formulations of mangane se on pea yield and 'marsh spot', a seed defect which reduces quality of peas (Pisum sativum) grown for human consumption or seed was evalua ted in nine experiments in the East of England from 1992 to 1994. Spra ys, at dose rates recommended by the manufacturer, were applied to fie ld peas, cvs Maro or Bunting, on three occasions at the four node pea growth stage, first pod and 14 days later, or on two occasions at firs t pod stage and 14 days later. Although the sites selected had a previ ous history of marsh spot in pea crops, there were no visual foliar sy mptoms of manganese deficiency in peas grown in any year at any site. Applications of manganese did not increase yields compared with untrea ted peas and there was no effect on maturity. Marsh spot was negligibl e in untreated peas at sites where soils had the lowest levels of mang anese (22 and 44 mg/kg), thus soil analysis for manganese may be inapp ropriate as a guide to prediction of marsh spot problems. The three sp ray programmes, which included an early application of manganese at th e 4-5 node stage, gave no statistically significant improvements in ma rsh spot control. There was a good correlation between amounts of mang anese applied and reductions in marsh spot, and manganese sulphate, 31 % w/w at 3.1 kg/ha applied as a split dose, achieved the best control. An exception was the manganese carbonate 50% w/v formulation which ma y have been poorly assimilated by the plant. Chelated manganese as MnE DTA 6.4% w/v at the rates recommended by the manufacturer was inadequa te for control of marsh spot in all years.