The management of wheat, barley, and oat root systems

Under many conditions,the root system does not appear to limit crop growth or yield and is more than adequate for maintaining the supply of nutrients and water to the shoot.Reductions in the rate of uptake of soil resources such as water and nitrogen lead to changes in assimilate allocation,which can increase the size of the root system.Limitations to grain yield caused by inadequate rooting mainly occur when soil conditions such as compaction or root damage by soilborne pathogens prevent the plants from accessing the potentially available water and nutrients in the soil.Soil factors which have the largest effect on root growth are penetration resistance,pore distribution,and water and nutrient availability.Root attributes that are repeatedly linked to resource capture are root length,rooting depth,and degree of root -soil contact.There is genetic variation in rooting characteristics and this can be taken advantage of in breeding programs for environments where lodging or drought are problems.Currently we do not know how to manage root systems of wheat,barley,and oats in the way that we can manipulate their leaf canopies.We know that management decisions can affect root systems,but often we do not know the consequences for grain yield and quality.The operations that influence rooting include: rotation,variety choice,cultivations,seed rate,sowing date,nitrogen rate and timing,and plant growth regulator application.Matching the appropriate farming practices to soil,climate,and crop will therefore lessen the probability of root limitations.The unpredictability of climatic events and their interaction with soil type makes it dif .cult to prescribe the best farming practices for optimizing rooting systems.However an understanding of how root systems behave in changing environments allows the risks of root limitation to be minimized.