Growing Ontario's Corn

Nitrogen Applied in Skip-Row Pattern
Greg Stewart, OMAFRA Corn Specialist

Fine-tuning nitrogen management continues to be a priority for both cost-conscious and environmentally aware corn growers in Ontario. A switch to sidedress application rather than pre-plant broadcast of nitrogen fertilizer is often presented as a move that will allow growers to use nitrogen more efficiently. There can be several reasons behind this potential increase in nitrogen use efficiency. Growers on sandy soils may argue that delaying nitrogen applications until June reduces the risks of heavy rains in May moving nitrate below the rooting zone. Similarly, corn producers on heavy clay soils may want to avoid pre-plant applications of nitrogen in fear that wet periods may cause the soil to be waterlogged, resulting in N losses through denitrification. From my perspective, the more appealing reason for applying nitrogen in the sidedress window is the opportunity to use the pre-sidedress soil nitrate test to get a better idea of the amount of residual nitrate in the soil and therefore be able to adjust nitrogen application rates accordingly.

Table 1 The effect of ammonia injector knife spacing on corn yields within different tillage systems at two Illinois locations. Source: Illinois Agronomy Handbook 1999 – 2000. University of Illinois.
	Yield (bu/A)
Injector spacing (in.)	Plow	Chisel	Disk	No-till
DeKalb trials
30	159	157	163	146
60	158	157	157	143
Elwood trials
30	- - -	119	121	118
60	- - -	117	125	121
- - - = no data collected

In addition to, or perhaps for some, even more important, than the nitrogen use efficiency arguments, are the possibilities of reducing overall costs and increasing planting timeliness by sidedressing. Costs are reduced by capitalizing on the lower nitrogen prices often associated with anhydrous ammonia, compared to other nitrogen sources, and efficiencies are increased by eliminating one operation prior to the corn planting. Another option in trying to make N application as efficient as possible is to use sidedress applicators that apply nitrogen in a skip-row pattern, with an injector knife running down every other inter-row.

Studies in Illinois indicated that nitrogen (anhydrous ammonia) injected between every other row resulted in comparable yields to injection between every row. This finding was true regardless of the tillage system being used (see Table 1). In some cases, fear of moving to a skip-row system stemmed from situations where root growth was considered to be sub-optimal (i.e., no-till or perhaps in heavy soils). The Illinois data suggested that no-till situations were of no concern, which was also supported by Ontario research and demonstrations conducted by the Middlesex Soil and Crop Improvement Association. A number of these Middlesex sites were conducted under no-till conditions, and there was no negative yield response to the skip-row pattern compared to applying the nitrogen in every inter-row (see Table 2). The Illinois results also suggested the nitrogen application rate did not affect the performance of the skip-row system (see Table 3).

Werner Seegelken of the Middlesex SCIA summarized their findings in the following points:

1. 40% savings in fuel costs!

2. 50% decrease in wear on the applicator knives.

3. Only half as much chance for cultivator blight!

4. The little tractor can now pull the applicator. So the big tractor can be left with the tires set wide, there is no need to buy narrow tires for it, and the huge turning radius of the front wheel assist is no longer tramping corn.

5. Only half the investment is required for new, better technology for getting the anhydrous in the ground and closing the slot.

6. Less soil disturbance. This means less potential for soil erosion and a more level field for soybeans next year.

With this system, injector positions can be adjusted to avoid placing an injector in the wheel track. This is viewed as a real benefit with anhydrous, as getting a good seal when applying in any tire tracks is always more difficult. In following a six-row corn planter pattern, the three-injector system fits great, no wheel tracks to run in and no need to run injectors in the guess rows. When matching the driving pattern for a planter of 8, 12 or 16 rows, and if you want to avoid tire tracks, the outside two injectors must be adjusted tohalf-rate application, and will run in the guess row track twice (i.e., an 8-row planter requires a 5-shank applicator, similarly a 7-shank applicator applying guess rows twice would cover a 12-row planter.) Most operators suggest using a double-tube system to keep the system operating at capacity and to avoid the need to reduce travel speed. Use a double-tube knife with two hoses going to each knife; the outside knives would require only one hose to give the half-rate application.

Table 2 The effect of nitrogen injector spacing on corn yield on field sites in Middlesex County. Source: Middlesex County Soil and Crop Improvement Association.
Year	# of Trials	Skip Row(60 inchs pacing)	Every Row(30 inch spacing)
		corn yield (bu/ac @ 15.5%)
1999	4	150	151
1998	2	166	164
1997	5	123	123
Average		141	140

While most of the research is based on anhydrous ammonia, there is no reason to expect that other nitrogen forms could not be applied in a skip-row fashion. It is also worth noting that if you are using UAN and are therefore no longer concerned about sealing in the wheel track, you could avoid the need for running injectors in the guess rows. This would also reduce the number of injectors by one (i.e., 6 injectors would do for a 12-row planter; you would follow the planting pattern, but some injectors would run in wheel tracks).

Table 3 The effect of nitrogen injector spacing on corn yields at various nitrogen application rates at DeKalb, Illinois. Source: Illinois Agronomy Handbook 1999-2000. University of Illinois.
	Nitrogen	Rate	(lbs/acre)
Injector spacing (in.)	120	180	240
-------------------------- corn yield (bu/A) ---------------------------
30	171	176	181
60	170	171	182

Perhaps one word of caution is in order. If you are on heavy textured soils and operating a reduced tillage corn planting system, you may want to set up a few trials with the skip-row pattern compared to an every row pattern before adopting the idea for the whole farm. Also note that if you are moving to a sidedress system, be sure to provide some nitrogen (20-30 lbs N/acre) through the planter to ensure adequate N fertility to the young crop.