A weekly report prepared by the staff of the Ministry of Agriculture, Food and Rural Affairs (OMAFRA). If you require further information, regarding this report, call the Elora Resource Centre at 519-846-0941. Office hours: 8:30am to 4:30pm. For technical information, call the Agricultural Information Contact Centre at 1-877-424-1300 or visit the OMAFRA website: www.ontario.ca/omafra.
CROP REPORT NUTRIENT DEFICIENCIES IN SOYBEANS
Leaf yellowing and slow growth is evident in many fields. Stressful growing conditions will amplify nutrient deficiency symptoms, insect feeding, and disease symptoms. When plants are already stressed it’s even more important to manage deficiencies wherever possible. Fortunately, weather conditions over the next four to six weeks are more crucial to seed development than the first half of the growing season. Conditions from now on will play a bigger role in final yield than May or June.
Potassium (K)
Potassium (K) deficient leaves turn yellow along the leaf margins and may cup downward. Lower leaves are affected first.
Factors that limit root growth such as dry conditions and sidewall compaction will reduce K uptake. Under dry conditions roots are less able to take up K from the soil even if soil K levels are sufficient.
Water logged soils will also inhibit uptake. A soil test is the only reliable way to know if a field is truly low in K or only showing stress-induced potassium deficiencies. It’s also important to note that K deficiency symptoms may indicate soybean cyst nematode (SCN) feeding on the roots. When taking soil samples ask the lab to also test for SCN. It’s difficult to alleviate K deficiency now since foliar products cannot supply enough potassium through the leaf to rectify the problem.
A dry application of potash may still be warranted in severe cases. Yield response will depend on the amount of rainfall after application. Generally, fertilizing low testing fields can result in a yield increase of 3 to 5 bu/ac.
Manganese (Mn)
Symptoms of Mn deficiency are interveinal chlorosis (yellowing). Mn is immobile in the plant so symptoms will generally appear on the younger leaves first. One of the most significant factors affecting the availability of Mn is soil pH. As soil pH increases, Mn availability decreases. Deficiencies can also appear on eroded knolls where the pH is higher than the rest of the field.
The deficiency is most common on poorly-drained soils, especially clays and silt loams. High organic matter also ties up Mn.
Manganese is less soluble in well-aerated soils. This is why compacted areas (wheel tracks) are dark green while the rest of the field goes yellow. A foliar application of Mn works well to rectify the deficiency and can provide a 5 bu/ac yield response in severe cases.
Visit fieldcropNews.com/2017/07/crop-report-july-13-2017/ for full article and descriptions.
COMING EVENTS
Aug. 2, 9 – Elora, Day 2, 3 – Growing Forward 2 – Growing Your Farm Profits (GYFP) – Planning for Business Success. Visit ontariosoilcrop.org or call 519-955-3139 for location of workshop or more information.
Aug. 11 to 13 – Drayton Fair (Peel/Maryborough/Drayton Agricultural Society). For more information, call Amy Hennesey at 519-932-2646 or e-mail draytonfair@hotmail.com or visit the website – www.draytonfair.com.
Aug. 11 to 13 – Hanover Fair (Hanover/Bentinck/Brant Agricultural Society). For more information, please call Doreen Schultz or e-mail hanoverfair@hotmail.com or visit hanoverfair.ca
Aug. 22 to 23 – The Costs and Consequences of Soil Degradation – Delta Hotel, Guelph. For more information and to register, visit soilcc.ca/soilsummit/2017 or call 204-792-2424.
