Crop Scene Investigation - 7 Solved: Tracking down suspects in Alistair's alfalfa

Wednesday, January 16, 2008

By DAVID TOWNSEND

Planting depth caused poor emergence in Alistair's alfalfa.

To be more specific, the seed was planted too deeply. Alfalfa must be planted in the top quarter-inch of soil for a successful stand.

You must pay particular attention to your field conditions at planting in order to get seed this shallow. A quick and easy test is that your heel shouldn't sink more than 3/8 of an inch into the seedbed. Another key to alfalfa establishment is that you pack, plant and pack again.

In Alistair's case, he didn't pack ahead of time. He planted into really fluffy soil, which caused the seed to go too deep. Where the tractor duals initially ran over the field, the coulter cart and openers didn't open the soil as deeply and the seed was appropriately placed. In effect, the tractor duals acted like a packer and prevented the seed from going too far.

The nicely emerged alfalfa on the headlands also supports the practice of packing. There was good emergence in this part of Alistair's field because the turning traffic created a packing effect.

And what about the difference across the field? It seems that the alfalfa planted earlier in the day didn't do as well as the alfalfa planted later in the afternoon. Soil type and planting depth come into play here. Better emergence occurred on heavier clay soil, where the coulter cart didn't sink into the soil as deeply.

Alistair had started replanting by the time I reached the field. Having solved the case at the sight of the tractor tracks, I suggested making a few equipment adjustments. Alistair hesitated to make modifications as he didn't have this problem before. I convinced him the soil was acting differently this year.

The field was fairly packed by this time, so we simply lifted the coulter cart up to about half an inch so it wasn't working the soil as deeply. And we took the disc openers and lifted them right out of the ground. The alfalfa was sprinkled on top of the soil and packed afterwards. The stand emerged without any problems this time.

Help your alfalfa crop achieve its quality and yield potential. Packing before and after you plant will ensure a thick and vigorous stand for years of good production.

Congratulations to Kory Lorentz, St. Clements for his correct answer. BF

David Townsend, CCA, is Technical Information Manager for NK® Brand, Syngenta Seeds.