SHOOTING for the big yields and high returns is constantly throwing up challenges for farmers in the Tenindewa TopCrop group, according to its leader Mike Doherty. Helping meet those challenges, says Mike, is where the TopCrop principal comes into its own. One of the longest running TopCrop groups in the state, the Tenindewa team was named joint winner of the state's best group, sharing the mantle with the Kunjin group, near Corrigin. Formed in 1994, it has played a major role in the steady increase in average yields for farmers involved. "We are continuous cropping on some pretty poor soil, which is a challenge," he said. "In this system, we are finding limiting factors popping up all over the place, and we are almost having to find the answers to questions we don't even know." Mr Doherty said the system was uncovering deficiencies, such as potash, which became obvious when growing a four-tonne crop, not when growing a two-tonne crop. He said monitoring and analysing these and why they occur through the TopCrop groups had allowed the problems to be addressed as they occurred. "It is all part of being aware of the difference and knowing how to handle them," he said. One of the major concerns for the group is herbicide resistance, with threats in both ryegrass and radish. Mr Doherty said the wheat/lupin rotation that had been used in the area in the past had place pressure on managing these weeds and created disease pressure for the lupin crops This rotation has now been widened with the uptake of canola by many growers, slotting in a wheat-lupin/wheat/canola rotation, allowing three goes at radish control in particular. "But we would really love another legume to fit in the rotation here," he said. This year has also thrown up some questions regarding the canola, with many farmers only relatively new to the crop. Indifferent establishment on some farms prompted a short field day last month, where variables such as seeding rates, nitrogen application and depth and time of sowing were all discussed. "We still have a lot to sort out about growing canola," Mr Doherty said. "Results have told us that sowing it in mid-April is best for yield and oil but, up here, sowing at that time runs into temperatures of 30-40°C." Mr Doherty, who crops about 3500 hectares (8500 acres) of his own, is hoping, with the development of technology such as yield monitors and maps, some of the problems and answers will become a bit more clear. "We really need to be able to know what is going right or wrong, and why some areas of the paddock might be going 6t/ha, and other 2t/ha," he said.