Control of manganese deficiency in field peas grown for seed or human consumption

The effect of foliar applications of different formulations of manganese on pea yield and 'marsh spot', a seed defect which reduces quality of peas (Pisum sativum) grown for human consumption or seed was evaluated in nine experiments in the East of England from 1992 to 1994. Sprays, at dose rates recommended by the manufacturer, were applied to field 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 first pod stage and 14 days later. Although the sites selected had a previous history of marsh spot in pea crops, there were no visual foliar symptoms of manganese deficiency in peas grown in any year at any site. Applications of manganese did not increase yields compared with untreated peas and there was no effect on maturity. Marsh spot was negligible in untreated peas at sites where soils had the lowest levels of manganese (22 and 44 mg/kg), thus soil analysis for manganese may be inappropriate as a guide to prediction of marsh spot problems. The three spray programmes, which included an early application of manganese at the 4-5 node stage, gave no statistically significant improvements in marsh spot control. There was a good correlation between amounts of manganese 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 may have been poorly assimilated by the plant. Chelated manganese as MnEDTA 6.4 % w/v at the rates recommended by the manufacturer was inadequate for control of marsh spot in all years.