study set 4

What are three crop characteristics that can be used to group crops into rotational units?

Crop botanical family Crop rooting depth Crop nutrient demands Crop pest/disease complexes

Name three reasons why knowing botanical families is useful for practitioners of sustainable agriculture

1) you know what pests and diseases to look for. 2) you can design crop rotations to disrupt pest and disease life cycles 3) you can identify wild relatives that might keep crop rotation from working for pest control Crops in the same family tend to have similar soil nutrient needs

Aside from making an agricultural ecosystem more resilient to disturbances, what are some other reasons that biodiversity is helpful in agriculture?

A diverse collection of organisms plays several roles in agriculture, including: Nutrient cycling (recycling organic matter - think the nitrogen cycle) Detoxifying or breaking down contaminants Biological pest control Pollination

Crop rotation provides some of the benefits of a polyculture system as well as some of the benefits of a monoculture system. Explain what crop rotation is, and list at least 3 reasons that crop rotation is a good idea.

Crop rotation is a planned system of growing different crops in succession on the same piece of land. Rotation provides some of the benefits of polycultures: increased biodiversity, yield stability and more efficient and complete use of resources, but usually only over time - not within a growing season. (Note - It doesn't give much protection against crop failure within a given year!). Within a growing season, a crop in rotation can be grown as a monoculture. The primary benefit is ease of management because of uniform crop needs, harvest time, and growth habit.

For each of the following plant families, list at least 2 crops that belong to that family. Cucurbitaceae: Poaceae: Brassicaceae: Asteraceae: Alliaceae Apiaceae: Rosaceae: Solanaceae: Fabaceae:

Cucurbitaceae: cucumber, squash, melon Poaceae: corn, sugarcane, bamboo Brassicaceae: cabbage, broccoli, kale Astereaceae: lettuce, sunflower, artichoke Alliaceae: onion, garlic, chives Apiaceae: carrot, celery, dill, cilantro Rosaceae: apples, berries, perennials Solanaceae: tomato, eggplant, tobacco Fabaceae: beans, peas, lentils, forages

Name two reasons why many organic vegetable farms have overly high levels of phosphorus in their soils.

Many organic farmers fertilize with manure. Manure has similar levels of N and P. Most farmers fertilize based on crop nitrogen needs. Crops use far lees N than P so by fertilizing with manure one is applying P at a rate beyond which plants can use. Solutions-switch to a fertilizer with low P for some time like blood meal or soybean meal.

Why might use of an organic fertilizer promote more soil biodiversity than a highly soluble conventional fertilizer would?

Organic fertilizers require microorganisms to mineralize the nutrients found in the fertilizer. Synthetic fertilizers contain readily available form of plant nutrients-do not require any microbes to make them available. The organic fertilizers create distinct niches which will be occupied by a diverse mix of soil microbes.

Explain the difference between an overlap planting of two crops and planting a mixture of the same two crops. What are the advantages of each?

Overlap Planting Two or more crop species overlap for parts of their life cycles Advantages of Overlap Planting Makes good use of space Minimizes competition between crops One of the crops often benefits - improved moisture - organic matter residue Mixtures Growing two kinds of crop at the same time on the same piece of land Conserves water & nutrient resources - More biodiversity provides better yields Mixtures of forage crops increase production season Forage = feed crop for animals Mixtures of grasses and legume forages increases feed quality AND erosion control

Define polyculture. List the advantages and disadvantages of polyculture, as compared with monoculture.

Polyculture = the cultivation of more than one crop species on the same piece of land in various temporal and spatial patterns (over time and space) Advantages: slows spread of pests, more stable yield, insurance against crop failure of one crop, resources in the ecosystem are used more efficiently Disadvantages: complicated agronomic management, more host species may mean more pests and diseases at any one time. (The advantages tend to outweigh the disadvantages!).

If you had a choice between a two-year rotation (lettuce-tomato-lettuce-tomato) and a four-year rotation (lettuce-tomato-bean-onion), which would you choose and why?

The four-year rotation is better, for several reasons: -more time between similar crops, better chance of avoiding disease problems -less soil depletion because different crops place different demands on the soil -more crops are grown, so more biodiversity

What are some ways that farmers promote or limit biodiversity on their farm?

monocultures (low levels of "planned biodiversity") frequent disruption of habitats broad-spectrum pesticides Promote biodiversity: Varied land use near fields (hedgerows, woodlands etc) Beneficial insectaries Use organic sources of nutrients that require microbes to break them down Plant many types of crops