is pH perhaps the culprit?

article by howard champ

It’s summer and in this awesome part of the world which also means that for a large portion of the agricultural sector it is prime growing season and the demand on our farmers to attend to their crops is endless, largely due to the pace at which the crops are growing due to the warm and often wet conditions. Due to the pace of the current growing season, crops are vulnerable to a variety of pests and diseases and because of the ideal growing conditions experienced at this time of year farmers have to keep a close eye on any unwanted symptoms in their crops so that they can react swiftly to reduce any further potential yield losses.

Often at this time of year, we at Nuvance get calls from various farmers to help identify problems with their crops. In my personal experience of late, I have been asked to visit several different farmers concerned about symptoms in their crops that are occurring. It can be quite challenging to pinpoint the cause of the symptoms and of course very disconcerting for the grower. Often disease symptoms and mineral deficiency symptoms can be confused and misdiagnosed. Great care is taken by the Nuvance sales representatives to investigate together with the farmer his/her cultural practices up until that point, to have a better understanding of the possible cause(s). It has become apparent recently that after in-depth discussions with the various farmers, that their cultural practices, including fertiliser and chemical application, mechanical maintenance are usually all up to scratch except for one, that is being overlooked namely soil pH! Farmers are fully aware of the importance of soil pH so there is no need to explain this, but often this can be overlooked and to save costs growers are tempted to rectify the pH ‘next season’. I have seen crops that have been well attended and money has been spent on correct fertiliser application but the crop at an early stage begins to show symptoms of specific mineral deficiencies. Magnesium, for instance, does not like acidic soils and is less available to the plant at a certain pH whilst the majority of other minerals are still available to the plant and will indeed be taken up by the plant resulting

RANGE OF ACIDITY RANGE OF ALKALINITY

The influence of soil pH on nutrient availability

in an imbalance and this is when symptoms begin to emerge. The table below shows the availability of certain minerals under different pH conditions.

Ideally soil pH needs to be around 6.0 to 6.5 for optimum growing conditions, but you can already see that within this range the availability of ‘phosphorus’, ‘calcium’, ‘magnesium’ and the trace element of ‘molybdenum’ is reduced. Hydroponic growers are gauging the pH of their water, daily and this is optimum management when it comes to pH control. This is not a practical management tool for growers producing crops in the soil, so they are encouraged to have their targeted soil’s pH checked at least once annually.

Often these growers are under pressure to utilise their soils continuously and as a result of constant cropping and fertiliser application, the residuals can create a more acidic environment where certain minerals are no longer as effective as they used to be. Please remember to regularly submit soil samples to your preferred laboratory so that you can make an informed decision to rectify the soil pH, based on the test results. Some soils could be costly to rectify, but if not done, then the problem will only deteriorate even further, in other cases it may only be a case of light annual maintenance. Goodluck!