NOVEMBER WEATHER:			Soil Temperature (oF)
	Air Temp. (oF)	Humidity (%)	4" (Bare)	4" (Sod)
Monthly Average High	52.3	97.3	45.8	44.7
Monthly Average Low	32.6	50.7	40.8	41.1
Observed High (date)	72(9)	100(several)	59(10)	54(8)
Observed Low (date)	18(3)	20(10)	35(4,23)	36(several)

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2006 Precipitation (in inches)

Month	Monthly Total	Monthly Departure from Average	Since January 1 Total Accumulation		Since January 1 Total Departure
January	2.91	+1.29	2.91		+1.29
February	0.36	- 1.36	3.27		+0.07
March	4.17	+1.32	7.44		+1.25
April	3.21	- 0.55	10.65		+0.70
May	1.47	- 2.80	12.12		- 2.10
June	2.38	- 1.88	14.50		- 3.98
July	1.65	- 2.68	16.15		- 6.66
August	3.67	- 0.35	19.82		- 7.01
September	1.31	-2.14	21.13		-9.15
October	2.45	-0.52	23.58		-9.67
November	3.73	+0.99	27.31		-8.68

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Crop Rotation: Can I Afford It or Not?

The discussion about rotating crops and the number of crops has probably been ongoing since farmers started putting seeds in the ground and comparing results over coffee. The benefits of rotating crops have been demonstrated for managing insects, weed and diseases for many crops. While some areas can profitably grow multiple crops, the corn/soybean rotation is the most common in Illinois, with some considering continuous corn to be the most profitable based on the rising corn price.

To address this question, a crop rotation study was established at NWRC that compares continuous corn and continuous soybeans, a 2 crop rotation of corn/soybean, and a 3 crop rotation with wheat/corn/soybeans. Each rotation has a tillage split of tilled (fall chisel/spring field cultivated) and no-till.

The yield results for each crop in the rotation sequences are shown in Table 1. The yields are averages of four or more years of data. Comparisons of the profitability of each crop rotation were made using these yields, times grain prices a year ago and current, less input costs of seed, fertilizer and herbicide. The total input costs used for each crop were: corn $185, soybeans $53, and wheat $64 were based on the averages of inputs for three years. In a farming operation, the input costs for rotated corn would be less than continuous corn, and wheat input costs could be lower with a reduction from 80 lbs. of N applied. The grain prices used were local prices on 11/29/2005 and 11/30/2006. Obviously, prices of inputs will be different for each farming operation, and in combination with changing grain prices the comparisons of different crop rotations will change.

Another change that would hopefully be different in a farming operation would be the use of a soybean cyst nematode (SCN) resistant soybean variety. The soybean yield data in these results are from using SCN susceptible varieties; planted to compare the influence of crop rotation on SCN populations. The change to using SCN resistant varieties was made this season, and yields were 10 to 20 bushels per acre (bpa) greater than these data from SCN susceptible varieties. Yields with the resistant varieties will be included in this comparison as we get more years of data.

One of the first things to notice with this data is when wheat is included in the rotation, corn and soybean yields are increased 7 to11 bpa, and 5 to7 bpa, respectively. These yield increases make the profitability of the 3 crop rotation almost identical to the 2 crop rotation when using last year’s prices, especially with the ‘wheat after soybean’ cropping sequence. However, when using this year’s prices the profitability is a little better with the 2 crop rotation.

One of the reasons for the increase in soybean yields with the 3 crop rotation is the reduction of SCN population. The population of SCN decreased from 11,240 eggs per 100 cc of soil in continuous soybeans to 5,920 eggs in the 2 crop rotation, to 2310 in the 3 crop rotation. This reduction in SCN population is due to the extra year out of soybeans since SCN susceptible varieties were used. It is not clear how SCN management with a resistant variety will interact with crop rotation, although the average population was reduced by ½ this first season with a SCN resistant variety.

From this data it is apparent there is a lag in corn yield and profitability of the continuous corn rotation to the other crop rotations. The use of genetic rootworm control with the hybrid Sieben 2563 YGPL improved the continuous corn yield this year, although it was still 23 to 30 bpa less than the corn yield in the other rotations.

There were no significant differences in yields between no-till and tilled systems with the 2 and 3 crop rotations for corn and soybeans, although no-till corn yields tended to be lower. No-till continuous corn yield and profitability was less than when tilled. Tillage did not have an affect on soybean yield, and wheat yielded better with tillage.

A way to make this information more applicable to an individual farm would be to apply “personalized” input costs and grain prices to these yield data. Or if these yields are not close to what occurs on a farm, take the relative yield differences between the different rotation and tillage systems to calculate the profitability for different systems on a farm.

Table 1: Crop rotation and tillage study with corn, soybeans and wheat at NWRC, Monmouth, IL.
Rotation Sequence	Tillage	Yield (bu/acre)(1)			2005 Avg. Yearly Net ($/acre) (2)	2006 Avg. Yearly Net ($/acre) (3)
		Corn	Soybean	Wheat
c/c/c	ct	122			64	239
	nt	103			16	172
s/s/s	ct		50		218	267
	nt		51		222	273
c/s	ct	184	53		222	371
	nt	179	52		215	360
w/c/s	ct	196	57	82	223	360
	nt	189	58	88	215	347
w/s/c	ct	191	59	76	216	350
	nt	185	60	71	209	337
LSD 0.05		7.4	2.3	2.6
1. Yield averages of 5 years for corn, 4 years of SCN susceptible soybeans, and 7 years of wheat.
2. Input costs include seed (YGPL corn in 2006), fertilizer (N at $0.40/lb), and herbicide.
3. Grain Prices 11/29/2005: corn $2:09, soybeans $5.32, and wheat $2.75.
4. Grain Prices 11/30/2006: corn $3.48, soybeans $6.44, and wheat $4.03.

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