7.6 Other approaches to agriculture

Alternatives to conventional agriculture

Before examining practices that are not used in conventional agriculture, recall that conventional agriculture is not a monolith. Practices such as cover cropping, precision agriculture, and no-till are increasingly widespread, and increase the sustainability of intensive agriculture. Some of the practices that follow can and are incorporated into so-called conventional agriculture.

Organic farming

The basics

Organic agriculture can be defined as an ecological production management system that promotes and enhances biodiversity, biological cycles, and soil biological activity. But it can also be defined by what is legally permitted in food labeled as organic in a given place. Organic meat, poultry, eggs, and dairy products come from animals without antibiotics or growth hormones. Organic food is produced without using most conventional pesticides, fertilizers made with synthetic ingredients or sewage sludge, or GMOs. The motivation behind organic production is often stated as prioritizing use of renewable resources, and conserving soil and water to enhance environmental quality for future generations, but this is obviously not part of a legal definition, and organic farming creates its own kinds of environmental impacts, some of which can be severe.

Organic farming replaces synthetic chemical fertilizers with naturally occurring materials. Animal manure and compost are often mainstay fertilizers. Additional nutrients may be added using bone meal, blood meal, and fish emulsion from animal processing; seaweeds and meals from plant processing (cottonseed meal, for example); or mineral-based material such as crushed limestone. Organic fertilizers can lead to eutrophication of nearby waters, just as synthetic fertilizers can. Manure, used in both conventional and organic farming, is particularly prone to leaching and can be heavily applied in either context, resulting in eutrophication of area waters.

Can we feed the world with organic farming?

The short answer is “no.” Presently, only a small fraction of world agriculture uses organic approaches, and converting all the rest of world agriculture is infeasible in the short term.

Presently, organic produce costs more than produce without that label, due to higher labor costs, lower yields (on average), costs associated with certification, smaller supply chains and markets, and the economics of smaller farms. The price differential for the “organic” label is needed to support farms that grow organic produce, but the price differential also puts much organic produce out of the reach of less affluent individuals. Farmers using non-organic production techniques have significant income “sunk” into their equipment and land; they could not quickly finance equipment needed for organic production techniques, even if sufficient equipment could be produced on short notice. Conventional farmers are not trained in organic practices and would need education. The land would need time to build resources – even no-till, which is increasingly widely adopted in conventional agriculture, needs several years before the benefits of no-till are well established and yields reach a new equilibrium.

A slower-paced conversion to organic practices might be more practical, but would not address the yield differential between organic and conventional farming that is the result of organic farming’s avoidance of synthetic fertilizers and pesticides and genetically modified organisms. If existing agricultural land were all converted to organic production, an additional 18% of land (approximately) would be needed to address the yield gap between conventional and organic approaches (18% on average across crop types, locations, and climates)^[1]. It’s not clear where that land would come from; it’s not likely new agricultural lands would be highly productive because most highly productive land is already in service to agriculture. New land might not be in places where organic requirements could be met or monitored.

Although we cannot presently feed the world with organic farming, that does not mean we cannot transition to less harmful agricultural practices, including lessons learned from organic farming. We already see such transitions in the use of no-till, crop rotation, and cover crops in conventional farming and the interest in creating crop varieties that will respond well to organic farming and reduce the yield gap with conventional farming.

Integrated pest management

Integrated pest management (IPM) refers to a mix of approaches to control of weeds and plant pests to reduce the occurrence of these agricultural problems and to address them when they reach levels of concern. IPM is used across the types of conventional and organic farming, but in conventional approaches, IPM includes synthetic control chemicals, whereas in organic farming, naturally occurring controls are used, including fairly toxic compounds such as pyrethrins (developed from chrysanthemums), Bt proteins (developed from a bacterium), neem oil (from the neem tree), and naturally occurring copper and sulfur compounds.

The first effort in IPM is to avoid high concentrations of weeds and pests so that control of outbreaks with toxins is less necessary. Crop rotation – planting different crops in the same field over time – breaks the cycle of crop-specific pests so that they and their eggs or young do not build up in soil or crop wastes. It may require farmers to have equipment for different crops on hand, simultaneously, which can increase costs, but may be balanced by higher yields with less effort. It also requires that farmers not continuously plant the most economically valuable crop in their repertory, which decreases income but may eliminate the chance that crop-specific pests become resistant to methods used to suppress them. But until resistance appears, it can be hard to convince producers to forego the income associated with continuous planting of a single, valuable crop.

Breeding of crop varieties that are resistant to harm from pests and that compete well with weed species is also helpful, as we saw with GMO varieties of major crop plants that incorporate Bt genes. The use of native biocontrols – breeding and deployment of large numbers of so-called “good bugs” and planting of habitat to support them is another means of reducing use of toxic chemicals, as we saw in the previous section.

Multiple crops in sequence – crop rotation

As we have just seen, crop rotation can be useful to break pest cycles and reduce the need for pesticides. In the midwestern US, corn is often grown in rotation with soybeans, to reduce damage from corn borers, which can cause considerable damage if corn is grown continuously. Another benefit of crop rotations that include a nitrogen-fixing legume such as soybeans is that legumes are able to fix nitrogen from the atmosphere, with the assistance of bacteria that they house in root nodules. Legume crops reduce the need for synthetic fertilizers. Clover and vetch are common examples of legumes that can be grown as a cover crops or as a hay crop, alternating with commercial food crops.

Any use of multiple crops, whether for cover crops, in crop rotation, or in simultaneous crops (see below) requires either equipment or labor to deal with multiple crops. To be profitable, the advantages of multiple crops must outweigh these additional costs.

Polyculture – multiple simultaneous crops 

Whereas crop rotation uses multiple crops in sequence, polyculture uses multiple crops simultaneously, and may also incorporate livestock. Where multiple crops are grown, the process of planting and harvesting becomes more complex. Crop rotation required the use of different equipment in different planting rotations. In contrast, polyculture requires different approaches for each product, and at the same time. The simplest systems still permit use of machines, but more complex systems may be worked primarily by hand labor. Farm labor is unequally available among nations.^[2] In addition, the ability to work outdoors is increasingly affected by climate change, which is making many tropical areas too hot for safe outdoor work during the hottest part of the day.^[3]

Intercropping

Intercropping is a form of polyculture. In intercropping, two or more crops are grown in close proximity to each other during part or all of their life cycles to promote soil improvement, biodiversity, and pest management. Incorporating intercropping principles into an agricultural operation increases diversity in soil, crops, and insects and other invertebrates (Fig 1). Different crops may have roots that reach nutrients and water at different depths; they may attract or repel different insects, and they may support soil organisms differently. Crops grown in intercropping are subject to fewer pest outbreaks,  and can improve nutrient cycling and crop nutrient uptake, and increase productivity. This approach can be particularly useful in more arid settings.^[4]

Agroforestry

Agroforestry is an intercropping system that includes woody plants. Shade-grown coffee is an example that many have heard of. Coffee originated in Ethiopia and was not originally a sun-tolerant plant; growing the coffee trees in the shade – either of a existing forest or together with other, taller crop-producing trees that can provide shade – was required. More recently, sun-grown varieties have been created to increase yield, but these require clearcutting of existing forests and more synthetics pesticides and fertilizers.

Shade-grown coffee systems are more forest-like, which retains more soil moisture, lowers temperature, supports greater biodiversity (including birds that eat coffee borer beetles) and, according to coffee lovers, improves the flavor of the coffee. The beans are considered to be of a higher quality and can be marketed for higher prices, although the balance of economic benefits and costs (from reduced yields) is not completely clear.^[5]

Agroforestry has considerable flexibility and can include woody plants grown for crops or for timber, non-woody crops, and may also include animals that graze or browse in the vegetation. Woody plants may form a somewhat continuous overstory or may be islands in a sea of non-woody plants (and animals).^[6] Subsistence food, fodder for livestock, building materials, fuel for cooking fires, and marketable products may all be produced. Agroforestry is often used by small-holders, and is considered important for food security in rural and developing areas. Nitrogen-fixing plants, including leguminous trees, can be included, and are a natural source of increased soil fertility, particularly important where financial concerns may limit purchase of fertilizers.

Agroforestry systems may be as simple as planted lines of trees and shrubs (called alley cropping) or as complex as mixed trees, agricultural crops, and forage crops, intermingled in less orderly ways (Fig 3). The more complex the arrangement of resources, the less likely it is that automation and technology can assist with any phase of growing or harvesting. This is another reason agroforestry is more common on small holdings and in areas where human labor is readily available.

Knowledge Check

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