* April trade data due Wednesday * Increases expected for most commodities, copper to dip * Pressure on manufacturing may cap growth in Q2 By Fayen Wong SHANGHAI, May 6 (Reuters) - China's main commodity imports are expected to rise in April from a month ago, supported by a seasonal recovery in demand, but the pace of growth in the second quarter will likely be capped by constraints on manufacturing. China will release preliminary April trade data on Wednesday. Shipments of crude oil, iron ore and soybeans are all likely to have climbed for a second month, after shipments fell in February due to a week-long holiday, although copper arrivals may ease slightly due to port strikes in top exporter Chile, traders said. "We should see an overall trend of gradual improvement. Fixed-asset investment grew quite strongly in March and should continue to accelerate, which will bode well for iron ore and copper," said Judy Zhu, a commodities analyst with Standard Chartered. "But the manufacturing sector w

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