Shares in Sirius Minerals rose after the potash miner said a study showed its Poly4 fertiliser to be 'effective and valuable' for commercial use on crops.The study by Durham University indicated that Poly4 helped accelerate the early stage of corn growth and reduce the risk of seedling disease. Results revealed Poly4 outperformed MOP when comparing the aerial dry weight of young wheat growth in two varieties tested."This latest set of impressive results continue to confirm that POLY4 is a valuable and effective multi-nutrient fertiliser," said Managing Director Chris Fraser. "I have no doubt that polyhalite will play a major role in helping to meet the increasing global demand for food."Shares rose 5.45% to 14.50p at 13:54 on Monday.RD