By David Jones, CropNuts Broad Acre Agronomist
“Well Sown is Half Grown!” is an old saying about the importance of planting the crop well to give it the best chance in life. As we approach planting season it is important to remind ourselves how to get it right, and why we should not rush if the soil and seedbed conditions are not satisfactory.
In Part 1 of our newsletter we tackled on the importance of soil sampling before planting. This week we take a look at why late germination matters to your crop yields, and how to avoid delayed emerging plants. But firstly, the causes of un-even germination:
- Cloddy seed beds – be patient! Wait for rain if the clods are too large, to work the seedbed again if necessary. Always better to plant well than to plant early and unevenly.
- Uneven planting depth – ensure depth wheels, linkages and planter setup are all correct. Operating speed is also a major cause of uneven seed depth. Slowing from 8 to 6kph can reduce the variation in seed depth placement by half in my experience.
- Variable soil moisture and temperature. This cannot always be avoided, but even residue cover is a crucial factor in notill systems. If you cannot get it right, consider row cleaners from companies such as Montag or Yetter so that after planting at least, the soil temperature will be more even.
In one Canadian study over several years, no-till maize took on average 2 days longer to emerge than cultivated soil because of the lower temperatures. This is not a problem – as long as all of the crop emerges at the same time.
Surely all the plants catch up eventually, does it really matter?
Yes it does matter. The best research I have seen is from Wisconsin State in the US, where by the way the state record yield in 2017 was an astonishing 19.8 t/ha or 88 bags per acre.
Researchers in Wisconsin set up a series of experiments where they planted varying proportions of a crop on time and delayed.
For example, 75% of the plants in one plot were planted on the optimum date, then they came back 1 ½ weeks later and planted the other 25% to mimic later germination. This allowed them to measure the overall effect on yield.
The results showed a 6% yield loss. This increased to a 10% yield loss when the 25% of late plants came up 3 weeks later. Just to prove the point, where they planted ALL of the seeds 10 days late in a separate plot to produce an even stand, it was only 5% lower yield than the evenly emerged, early planted crop. Planting well is more important than planting on the perceived ‘optimum’ date.
The summary of results compared to the ‘perfect’ establishment represented by the black bar on the chart below is a strong visual reminder of the yield cost of poor planting.
So, if you have a significant proportion of the crop germinating late over 200 hectares every year from an inaccurate planter, this will easily be costing you 5-10% of your yield. On an 8 t/ha (35 bag/acre) crop this is worth Ksh 22,000 ($220) per hectare and puts the cost of the planter into perspective.
When should I consider replanting an uneven crop?
That was not the whole story however… Where you have variation between the rows – which is very common when a couple of the units on the planter working too shallow, as pictured below from Pioneer USA – the yield loss is actually much less.
Even when 50% of the rows emerge late the yield loss is actually minimal – less than 5%. This is importance guidance when considering replanting. The bigger plants are sufficiently far away from the small plants in this case that the competition is minimal.
If more than a quarter of your plants WITHIN the rows have not emerged within 2 weeks of planting however, you might be better to replant if rain arrives and accept an 88% yield by planting late (the yellow boxes on the graph), rather than a 79-80% yield from a variable plant stand.
Till next time,
David Jones is the Broad Acre Specialist at Crop Nutrition Laboratory Services Ltd. (CROPNUTS). David has a keen interest in soils and no till farming systems where he has undertaken work looking into weed levels and changes in soil structure, and has extensive experience in field trials and in the development of precision farming techniques. In his spare time he enjoys playing rugby.