**2. Crop rotations vs. continuous cropping**

Crop rotation schemes are, by and large, regional in nature and a specific rotation in one environment may not be applicable in another. Continuous cropping schemes or monocultures for the most part, have fallen out of favor in many farming regions. Roth (1996) published mean corn yields from a 20 year crop rotation experiment in Pennsylvania that included rotation with both soybean and alfalfa showing higher yields with all rotation schemes than continuous corn (Table 3). The extensive use of commercial fertilizers and pesticides has helped mask most of the beneficial effects of crop rotation. But Karlen et al. (1994) has stated" no amount of chemical fertilizer or pesticide can be fully compensated for crop rotation effects". However, economics continues to be the large determining factor into how a field is managed.

until changes in government support programs in the mid-1990's that planters in the Mid South became interested in alternatives to continuous cotton and began to produce corn for commercial sale and rotate it with cotton. Corn hectareage in the states of Arkansas, Louisiana, and Mississippi increased from 161,000 ha in 1990, to 382,000 ha in 2000, to

Until 2007 research information about corn-cotton rotations were limited. An extensive study on various corn-cotton rotation schemes yielded data on the effects of rotation on yields and reniform nematode (*Rotylenchulus reniformis*) a serious pest to cotton. Bruns, et al. (2007), reported corn grain yields were greater following cotton than in plots of continuous corn. Pettigrew, et al. (2007), noted that cotton plant height increased 10% in plots following one year of corn and 13% following two years of corn when compared to continuous cotton (Table 4). Lint yields increased 13% following two years of corn primarily due to a 13% in bolls per m2. No other increases were noted however. Stetina, et al., (2007) found that following two years of corn production, reniform nematode populations remained below damaging levels to the cotton plants. However, cotton following just one year of corn would have reniform nematode populations rebound to damaging levels towards the end of

Yield(kg ha-1)

Cotton continuous cotton 1101a 1036a 1257 1266b corn-cotton-corn-cotton xxx 1068a xxx 1353ab cotton-corn-corn-cotton 1117a xxx xxx 1460a

Corn continuous corn 10,364a 10,107b 7587a 9032 corn-cotton-corn-cotton 10,297a xxx 8157a xxx cotton-corn-corn-cotton xxx 10,675a 7730a xxx

‡Within each crop and year, means followed by the same letter are not significantly different by lsd (P0.05) Table 4. Effect of crop rotation sequence on crop yield of corn and cotton from 2000 to 2003

Rice ranks third behind corn and wheat in total tons of grain produced in the world but it is the primary dietary staple for more people than any other cereal (Raun and Johnson, 1999). It is grown on every continent except Antarctica. By the 1990's rice was providing 35% to 59% of the total calories consumed by nearly 2.7 billion people in Asia (Neue, 1993). Peng et al. (1999) quoted that world rice production would need to be at least 600 million tons by 2025, an increase of 266 million tons above 1995 production just to maintain current nutrition levels. This increase will likely not be sufficient to alleviate current malnutrition in many of the rice dependent cultures (Neue, 1993). In areas where it is virtually the sole source of calories it is seldom grown in rotation with other crops. Anders, et al., (2004)

†Lint yield for cotton; grain yield at 155 g kg-1 seed moisture; all values are means of eight reps

sequence† 2000 2001 2002 2003

630,000 ha in 2010 (USDA-NASS, 2011).

the growing season.

Crop Rotation

averaged across four genotypes.

in Stoneville, MS. (Stetina et al., 2007).

**3. Rice production and crop rotation** 


†First year corn yield ‡Second year corn yield

Table 3. Mean corn grain yields as influence by crop rotation from 1969 to1989 at Rock Springs, PA. (Roth, 1996).

One primary benefit to crop rotation is the breaking of crop pest cycles. Roth (1996) states that in Pennsylvania, crop rotations help control several of the crop-disease problems common to the area such as gray leaf spot in corn (*Cercospora zeae-maydis)* take-all in wheat (*Gaeumannomyces graminis* var. tritici), and sclerotina in soybean (*Sclerotinia sclerotiorum)*. In corn, corn rootworms (*Diabrotica virgifera* spp.) can be a devastating pest and crop rotation was considered to be the most effect method of control. However, beginning in the late 1980's there was a variant of the Western corn root worm (D. *virgifera virgifera* LeConte) that began egg laying in soybean fields, making larvae present to feed upon first year corn in a soybean-corn rotation (Hammond et al., 2009). Prior to this time the standard method to avoiding rootworm damage was to rotate. However, during the mid-1960's in the Cornbelt there was a movement to engage in growing corn continuously on highly productive soils. Atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] was being readily adopted for weed control in corn and a number of insecticides were becoming available for of control corn rootworm and other corn insects. Also sources of nitrogen fertilizer were readily available and relatively inexpensive. Competitive profits for other crops, particularly soybean, and continued research showing tangible benefits to rotations though returned most fields to some sort of rotation scheme. However, there are some producers today who are profitable at growing continuous corn. But, such a system appears to require strict adherence to sound management practices.

Cotton is probably the principle crop that has been grown continuously on many fields, some for over 100 years. The crop was profitable and well suited for production in areas prone to hot summer temperatures and limited rainfall. There was also an infrastructure available in these production regions for processing the lint and seed as well as a social bond that connected the crop to the people who grew it. Corn, hay, and small grains were the "step children" of agronomic crops for generations of southern planters. Corn and winter oats were grown in the Cottonbelt solely as feed grains for the draft animals used to grow cotton and the meat and dairy animals grown for home consumption. There were basically no markets available or facilities to handle some of these crops for commercial trade. Despite being introduced in the 1930's, it wasn't until the early 1950's that soybean became an important crop in the lower Mississippi River Valley (Bowman, 1986). Rice (*Oryza sativa* L.) was introduced to the Mississippi River Delta in 1948 and together these crops provided alternative sources of agronomic income to cotton but did little to encourage crop rotation. Both rice and soybean were relegated to the heavier clay soils of the Mississippi Delta with the sandy loams, silts, and silty clays remaining in cotton. It wasn't

Crop Rotation Yield Mg ha-1 Continuous corn 8.7 Corn/soybean 9.1 Corn/two-year alfalfa 9.6 Corn/corn/three-year alfalfa 9.6† Corn/corn/three-year alfalfa 9.3‡

Table 3. Mean corn grain yields as influence by crop rotation from 1969 to1989 at Rock

One primary benefit to crop rotation is the breaking of crop pest cycles. Roth (1996) states that in Pennsylvania, crop rotations help control several of the crop-disease problems common to the area such as gray leaf spot in corn (*Cercospora zeae-maydis)* take-all in wheat (*Gaeumannomyces graminis* var. tritici), and sclerotina in soybean (*Sclerotinia sclerotiorum)*. In corn, corn rootworms (*Diabrotica virgifera* spp.) can be a devastating pest and crop rotation was considered to be the most effect method of control. However, beginning in the late 1980's there was a variant of the Western corn root worm (D. *virgifera virgifera* LeConte) that began egg laying in soybean fields, making larvae present to feed upon first year corn in a soybean-corn rotation (Hammond et al., 2009). Prior to this time the standard method to avoiding rootworm damage was to rotate. However, during the mid-1960's in the Cornbelt there was a movement to engage in growing corn continuously on highly productive soils. Atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] was being readily adopted for weed control in corn and a number of insecticides were becoming available for of control corn rootworm and other corn insects. Also sources of nitrogen fertilizer were readily available and relatively inexpensive. Competitive profits for other crops, particularly soybean, and continued research showing tangible benefits to rotations though returned most fields to some sort of rotation scheme. However, there are some producers today who are profitable at growing continuous corn. But, such a system appears to require strict

Cotton is probably the principle crop that has been grown continuously on many fields, some for over 100 years. The crop was profitable and well suited for production in areas prone to hot summer temperatures and limited rainfall. There was also an infrastructure available in these production regions for processing the lint and seed as well as a social bond that connected the crop to the people who grew it. Corn, hay, and small grains were the "step children" of agronomic crops for generations of southern planters. Corn and winter oats were grown in the Cottonbelt solely as feed grains for the draft animals used to grow cotton and the meat and dairy animals grown for home consumption. There were basically no markets available or facilities to handle some of these crops for commercial trade. Despite being introduced in the 1930's, it wasn't until the early 1950's that soybean became an important crop in the lower Mississippi River Valley (Bowman, 1986). Rice (*Oryza sativa* L.) was introduced to the Mississippi River Delta in 1948 and together these crops provided alternative sources of agronomic income to cotton but did little to encourage crop rotation. Both rice and soybean were relegated to the heavier clay soils of the Mississippi Delta with the sandy loams, silts, and silty clays remaining in cotton. It wasn't

†First year corn yield ‡Second year corn yield

Springs, PA. (Roth, 1996).

adherence to sound management practices.

until changes in government support programs in the mid-1990's that planters in the Mid South became interested in alternatives to continuous cotton and began to produce corn for commercial sale and rotate it with cotton. Corn hectareage in the states of Arkansas, Louisiana, and Mississippi increased from 161,000 ha in 1990, to 382,000 ha in 2000, to 630,000 ha in 2010 (USDA-NASS, 2011).

Until 2007 research information about corn-cotton rotations were limited. An extensive study on various corn-cotton rotation schemes yielded data on the effects of rotation on yields and reniform nematode (*Rotylenchulus reniformis*) a serious pest to cotton. Bruns, et al. (2007), reported corn grain yields were greater following cotton than in plots of continuous corn. Pettigrew, et al. (2007), noted that cotton plant height increased 10% in plots following one year of corn and 13% following two years of corn when compared to continuous cotton (Table 4). Lint yields increased 13% following two years of corn primarily due to a 13% in bolls per m2. No other increases were noted however. Stetina, et al., (2007) found that following two years of corn production, reniform nematode populations remained below damaging levels to the cotton plants. However, cotton following just one year of corn would have reniform nematode populations rebound to damaging levels towards the end of the growing season.


 †Lint yield for cotton; grain yield at 155 g kg-1 seed moisture; all values are means of eight reps averaged across four genotypes.

‡Within each crop and year, means followed by the same letter are not significantly different by lsd (P0.05)

Table 4. Effect of crop rotation sequence on crop yield of corn and cotton from 2000 to 2003 in Stoneville, MS. (Stetina et al., 2007).
