Picture Credit: “Oats in conservation agriculture crop rotation, Mexico” by CIMMYT is licensed under CC BY-NC-SA 2.0

Source: https://en.wikipedia.org/wiki/Crop_rotation

‘Crop rotation’ is the practice of growing a series of different types of crops in the same area across a sequence of growing seasons. Growing the same crop in the same place for many years one after another, gradually depletes the soil of certain nutrients and selects for a highly competitive pest and weed community. Without balancing nutrient use and diversifying pest and weed communities, the productivity of monocultures is highly dependent on external inputs. Conversely, a well-designed crop rotation can reduce the need for synthetic fertilizers and herbicides by using ecosystem services from a diverse set of crops. Additionally, crop rotations can improve soil structure and organic matter, which reduces erosion and increases farm system resilience.

Quite simply, crop rotation reduces reliance on one set of nutrients, pest and weed pressure, and increases the probability of the avoiding the development of resistant pests and weeds. Growing the same crop in the same place year after year, will cause a build-up of pests and diseases specific to that crop. Once you realise that different crops consume different levels of nutrients from the soil and that ultimately the nutrients become unbalanced (less of one nutrient but an excess of another), the idea of crop rotation makes solid sense.

History

Agriculturalists have long recognised that suitable rotations—such as planting spring crops for livestock in place of grains for human consumption—make it possible to restore or to maintain a productive soil. Ancient Near Eastern farmers practiced crop rotation in 6000 BC without understanding the chemistry, alternately planting legumes and cereals. In the Bible, chapter 25 of the Book of Leviticus instructs the Israelites to observe a “Sabbath of the Land”. Every seventh year they would not till, prune or even control insects.

Author Valerie Hansen, in her book:The Year 1000: When Explorers Connected the Worldand Globalization Began (pages 19/20), wrote:

“The population of Western Europe also rose as the residents adopted far-reaching changes in agriculture, which the British historian R. I. Moore has called ‘cerealization.’ They planted more and more land with wheat and barley. In northern France and England, cultivators first recognised that raising the same crop in a given field year after year lowered its fertility, so they allowed one third to one half of their land to lie fallow.  

“After 1000, farmers began alternating their crops. One popular rotation was turnips, clover, and grain, which helped retain nutrients and soil quality. This practice, so important for raising agricultural yield, spread only slowly (it was already well known in China). At the same time, other innovations also increased output: horse-drawn ploughs, water mills, windmills, and iron tools that could dig deeper into the soil than wooden tools. Before cerealization, most of the land in Western Europe was not under regular cultivation; afterward much of it was.

“In addition to raising population, these changes contributed to the rise of settled communities in Europe. Before the growing of grain became widespread, many farmers in Western Europe had been itinerant, moving from place to place to work the land and raise livestock. This continued to be true of farmers in Scandinavia and Eastern Europe, who followed their herds of pigs, goats, sheep, cattle, and horses. But first in France, England, and Germany, and later in Eastern and Northern Europe, farmers began to build houses and settle down in villages, thanks to crop rotation and other agricultural advances.

Systems

Crop rotation makes a difference. But to get the best out of the soil, there are other factors too. In 1700, British gentleman farmer Jethro Tull invented the seed drill and thereby helped bring about a revolution in British farming. His horse-drawn seed economically sowed the seeds in neat rows (he later developed a horse-drawn hoe) and his methods were adopted by many farmers and helped to provide the basis for modern agriculture. Tull’s mechanical innovations were accompanied by a theory of plant nutrition including his rejection of the value of manures in maintaining soil fertility.

Against the grain…
Source: Page 62, National Trust Magazine Autumn 2020

The National Trust Magazine (Autumn 2020) has an article about nature thriving at Lodge Farm on the Harewoods Estate in the Surrey Hills where tenant farmer Mike Pinard grows varieties of heritage wheat as has been done since the 18th century. The oldest varieties, which can reach 5ft, have been planted there since 1650. A low-impact technique is used, called ‘no till’ farming.  The farmer explains:

“The method of ‘no till’ farming is not new. It borrows its technique from nature. We sow seeds directly into the earth using a special drill, which disturbs as little soil as possible. The drill cuts through old vegetation and creates a slot in the ground. Seeds are blown into the slot and a following wheel closes it and firms the ground around the seed. The old vegetation is left on the surface to feed the citizens of the soil (such as bacteria, fungi, worms and beetles) as the nutrients and organic matter end up back in the earth. This method sequesters a lot of carbon from the atmosphere as well.”

No-till and strip-tillage are both forms of conservation tillage. No till is the practice of never tilling a field. Tilling every other year is called rotational tillage. ‘No till’ farming, which started in the 1940s, is also known as zero tillage or direct drilling – it decreases the amount of soil erosion that tillage causes in certain soils, especially in sandy and dry soils on sloping terrain. Tillage may be dominant in agriculture today, but no-till methods can be successful too. In some cases, minimum tillage or ‘low-till methods combine till and no-till methods. For example, some approaches may use shallow cultivation (i.e. using a disc harrow) but no ploughing.

Martin Pollins
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