More knowledge of the adaptability of different crops root systems is therefore needed. Traditional root studies in uniform soil columns cannot replace field studies, since the importance of undisturbed soil structure is paramount. However, studies in maize have shown a close negative correlation between root density and nitrate residues in soil. Methods of fertiliser application, i.e. broadcast or placed, can only be used efficiently when the spatial distribution of roots is known. Monocots are efficient at penetrating hard pans, but they have little capacity to branch below the compacted layer.
Dicots act in the opposite manner.
We have much general knowledge, but little operative know-how of how to improve crop rooting. This gives rise to different amounts of mineral nitrogen in the soil at harvest. Large differences may also exist in the rooting depth of different cultivars of the same species. In peas this has been found to be related to variations in the onset of flowering, after which little root growth occurs. The previous crop may also affect rooting.