Crop rotation

Crop rotation refers to the planting of dissimilar crops in consecutive seasons in the same field. This is an age old organic practice in which the sequence of cropping benefits each successive crop in the field. Generally, crop rotation improves or maintains soil fertility, reduces the build up of crop-specific pests, reduces the need of chemical pesticides and fertilizers and increases net profits.

Usually, groups of dissimilar crops are planted one after the other – like cereals after legumes, deep-rooted after short-rooted plants etc. Planting the same crop the second time necessitates replenishing the nutrients that were consumed in the first planting. However, by rotating different crops with different nutritional requirements, the cultivator could get a good yield without adding too many fertilizers and supplements.

The second crop could either be one that requires a different set of nutrients, or one that is structurally different. For example, if a deep-rooted crop follows a shallow-rooted one, it could benefit from the fertilizers that have leached lower layers and are inaccessible to the shallow-rooted one.

Different rotation sequences are possible, based upon soil quality, temperature and availability of water. These sequences could be for two years or longer depending on the local conditions.

Did You Know?

• With Crop Rotation, one application of fertilizer may benefit two consecutive crops -- the first with shallow roots, and the second with deeper ones!
• For the same reason, it makes optimal use of water too.
• Crop Rotation ensures that the farmer does not put all his eggs in one proverbial basket.

Why Use Crop Rotation?

• Moving crops around helps to stop the build up of pests and diseases, which are found in the soil.
• Plants need nutrients in different amounts and take them from different parts of the soil. Changing the crops in an area means that nutrients in all parts of soil are used.
• Families of vegetables often need similar nutrients (food). Keeping families together means that crops get the best growing conditions.
• Some plants have dense foliage (leaves which are close together and lots of them). These plants help to stop weeds growing. Changing from plants that do not

have dense foliage, to those that do the next year, will help to keep the weeds down.

A sample crop rotation guide

The types of crops used and the time frame of the rotation sequence would depend upon many factors like climate, commercial considerations and soil quality. Here is a rough guide for a five year crop rotation sequence.

• First year: Plant potatoes. A good potato crop needs a lot of manure, which would prep up the soil for the remainder of the cycle.

• Second Year: Plant leeks, onions or garlic. This group of plants also needs a lot of manure or compost, for which the soil is already equipped from the potato crop. Additionally, if the farmer is interested in multiple cropping, he could plant other vegetables that need extra manure, like the gourds (pumpkin, bottle gourds, courgettes etc).

• Third Year: To replenish the soil, plant legumes like peas and beans. These fix the Nitrogen in the soil, readying it for the next crop.

• Fourth Year: Crops like cabbage, cauliflower and broccoli that need extra Nitrogen will grow well after a harvest of legumes.

• Fifth Year: Plant root vegetables like carrot, parsnips and beetroot, which can take advantage of soil nutrients lower under the ground. Wherever there is space, lettuce and other salad plants may be planted.

Advantages of Crop Rotation

The biggest advantage of crop rotation is that it allows for the most efficient use of the soil with minimum addition of fertilizers and pesticides. It improves the distribution of plant nutrients in the soil by varying the feeding range of roots.

Crop rotation improves soil quality especially when leguminous crops or green manure crops feature in the rotation sequence. Planning a rotation sequence, farmers often put a deep-rooted crop soon after a shallow-rooted crop. In so doing, they ensure that the nutrients that might have otherwise been lost to leaching get consumed by the deep roots of the second crop. Thus, crop rotation uses lesser manure and fertilizer than conventional cropping methods.

Continuous cropping depletes the soil of specific nutrients, while crop rotation allows the soil to remain in good physical condition. It also allows the buildup of organic matter in the soil.

Crop rotation is very conducive in reducing and often preventing the transmission of disease. Diseases like Bacterial Blight and Scab that affect wheat, barley, grasses and rye can be completely controlled by rotation alone.

It also helps to partially or even fully control weeds and some insect pests. For example Wheat stem maggot that destroys wheat crops may by easily controlled by rotation. (For a detailed list of diseases and pests that may be controlled by crop rotation, visit Pest and Diseases that Crop Rotation can Control)

It improves crop quality and yields by ten to fifteen per cent, and at the same time, reduces the farmer’s expenditure on fertilizer and pesticides.

Crop rotation promotes income diversity by reducing the farmer’s dependence on one crop alone. It also allows better use of the farmer’s labor and farm equipment.

Crop rotation improves soil water utilization. Alternating deep and shallow-rooted crops ensures that water is absorbed at different levels in different years. This allows the level depleted by one crop to be naturally replenished.

Another advantage of crop rotation is that it improves ground water quality since fewer chemicals reach beneath the earth surface to contaminate ground water. This also results in beneficial effects on the local flora and fauna. To see a statistical analysis of corn yields that improved with crop rotation, see Crop Rotation Statistics

References

• Cropping Systems
• [http://www.ag.ndsu.edu/pubs/plantsci/crops/eb48-1.htm
• Kansas Rural Centre
• Organic Gardening
• Crop Rotation

--Geetanjalikrishna 03:59, 3 September 2007 (EDT)