Monday, July 15, 2013

Emotional Rescue

Last Thursday Brian and I spent the day walking on top of, instead of through, corn fields like this one. Strong winds from Wednesday's storm blew down corn from just west of Rannoch through St Marys and followed a path across Embro, Hickson and Innerkip.  Hail was mostly confined to the town of St Marys causing more damage to vehicles sitting outside than to field crops, so we were spared that particular problem. The wind however left many magnificent fields laying in ruins.  By the end of the day we were both in need of some emotional rescue.  It had been a depressing day.
By Monday morning the same spot in the field pictured at the top looked like this.  Recovery was dramatic. There is still some goose necking and a few plants snapped off, but compared to last Thursday you would not believe it was the same field.
One clue that the plant had been on the ground is the mud caked on the top leaves.  The impact on yield will not be as large as it first appeared.  A summary of a two year trial looking at the effect of wind lodging vs stage of development can be found at this link.

The fact that the corn plants are in the vegetative growth stage of development is the reason for the quick recovery.  Last Wednesday a lot of corn was in the V8-V10 stage of growth.
A V10 corn plant looks like the plants above.  V10 just means there are 10 visual leaf collars.  A leaf collar is formed when the leaf is fully developed.  You have to remember to account for the bottom leaves that are no longer there because they were lost in the May 25-26 frost.
A V10 corn plant will have 12-13 leaves visible and 9-10 leaf collars.  A mature corn plant has 15-16 leaves.  If you carefully pull the plant apart you will find the rest of the leaves and tassel rolled up inside the whorl.
This V10 plant still has to push out three more leaves plus the tassel.  At his time of year you can expect a new leaf to emerge every three days.  3 leaves x 3 days is 9 days plus two more days for the tassel to fully emerge equals a total of 11 days of vegetative growth.  These 11 days give the plant time to recover from the wind damage, grow more roots, stretch upward to the sun and prepare for pollination.  This is why the actual yield loss from the wind damage will probably be less than 5%.  After tassel and pollination is complete the corn plant diverts all of its energy to grain development and yield losses due to storm damage increase dramatically.

Since we are talking plant physiology we should point out one more thing.  Ear shoots are visible in a V10 corn plant.  Carefully removing the leaves reveals ear shoot formation occurring at each node.  There is one dominant shoot that takes priority over the rest, but the plant prepares for the future by generating 4-5 ear shoots and if the environment allows it then has the ability to produce multiple ears.

This is a close up of the largest and most dominant ear shoot.  You can make out the beginnings of the new ear in the centre of the shoot.  Silks from the ear shoot will begin to emerge slightly ahead of the tassel emerging.  Every year the question is asked about why silks emerge ahead of the tassel.  It is normal and healthy for silks to emerge first because a corn silk will remain receptive to pollen much longer than a pollen grain can live.  A corn plant generates pollen for about 5-7 days and the plant starts extending the silks slightly ahead of the tassel to match the timing of maximum silk availability with maximum pollen shed.
So steadfast and true, the corn plant comes to our emotional rescue.

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