Agriculture: An Introduction

The warm climate and rich soil of southern Brazil made the area produce abundant harvests.

By 1990, the soil in the region

had been farmed so many times, its productivity was ruined.

Before then, farmers had tilled (plowed) the soil. This left the soil loose and vulnerable. The heavy rains in Brazil would wash away the soil.

Farming in Brazil

After 1990 farmers there then began turning to zero-tillage farming.

The farmers and scientists in Brazil came up with a method of planting ‘cover crops’ on the farmland to keep the soil intact, and then simply slicing a thin groove in the ground and dropping seeds in when it was time to plant a commercial crop.

This method reduced erosion in Brazil by 90%.

No–Till Brazil

reduces a farmer’s expenses because less fuel and labor are used to plant

reduces erosionthe soil holds more water and organic nutrientsplants grow better in no-till soil

No-Till Farming

Agriculture: the practice of raising crops and livestock for human use and consumption

Cropland: land used to raise plants for human use

Rangeland: land used for grazing livestock, also known as pasture

Soil: a complex plant-supporting system consisting of disintegrated rock, organic matter, water, gases, nutrients, and microorganisms

An Overview of Agriculture

By over-farming humans are greatly reducing its ability to support life for long time periods

Soil degradation can cause considerable environmental damage, for example turning grasslands into deserts

Degradation of Soils

For the 80 million people added to the Earth every year, it loses about 15 million acres of productive cropland

Europe currently has the highest proportion of degraded land of any other continent

Degraded Areas

Humans began using agriculture about 10,000 years ago.

Agriculture most likely began as the hunter-gatherers brought back seeds and nuts to their villages, some fell to the ground, began to grow, and people realized they could plant.

History of Agriculture

Farming using human and animal power is traditional agriculture.

Subsistence agriculture is a family farming only to produce enough for themselves.

Intensive traditional agriculture is farming to produce excess food to sell at market.

Traditional Agriculture

Replaced animal power in farming with machine power

Appeared after the Industrial Revolution

Boosted crop yields by intensifying irrigation and introducing synthetic fertilizers, while the creation of chemical pesticides reduced weeds and pests

Industrialized Agriculture

In order to be efficient, industrialized agriculture requires that vast areas be planted with only one type of crop.

The uniform planting of only a single crop is called monoculture.

Today, monoculture is used on over 25% of Earth’s croplands.

Monoculture

In the mid-1900s, a revolution was sparked around the world that encouraged the introduction of industrialized agriculture to developing nations.

This greatly increased the productivity of developing nations and helped many regions avoid starvation.

The Green Revolution

Parent Material: the base geological material in a particular location (rock/sediment/dunes/lava/volcanic ash)

Bedrock: the continuous mass of solid rock that makes up Earth’s crust.

Rock Terms

Erosion: the dislodging and movement of soil from one area to another.

Weathering: the physical, chemical, and biological processes that break down rocks and mineral, turning large particles into small particles (physical, chemical, & biological weathering).

Weathering & Erosion

Soil is made of roughly 50% mineral matter, 45% air and water, and 5% organic matter.

Formation begins when the lithosphere’s parent material is exposed to the effects of the atmosphere, hydrosphere, and biosphere.

Weathering, erosion, and the deposition and decomposition of organic matter are most responsible for the formation of soil.

The Formation of Soil

After small particles are produced from the parent material, wind, water, and organisms move and sort them.

Distinct layers of the particles begin to develop, and each layer is known as a soil horizon.

The vertical look at the layers, from the surface to the bedrock down below is known as a soil profile.

Soil, Soil

The six major horizons in a soil profile are the O, A, E, B, C, and R horizons.

The most important horizon in agriculture is the A horizon, more commonly referred to as topsoil. Topsoil is the most nutritive horizon for plants.

Horizons

Minerals move down through a soil profile in a process known as leaching

Leaching

Color

Texture

Structure

pH

How is Soil Characterized?

Soil color indicates its composition and fertility. Dark soils are usually rich in organic matter, while gray to white soils often mean leaching occurred or there is low organic matter.

Color

Soil texture is determined by the size of the particles.

‘Clay’ consists of particles less than 0.002 mm in diameter, ‘silt’ particles 0.002-0.05 mm, and ‘sand’ particles 0.05-2.00 mm.

Soil with a relatively even mixture of all three textures is called loam.

Texture

Soil structure is a measure of the ‘clumpiness’ of the soil.

Structure

Soil pH is the degree of acidity or alkalinity of the soil.

pH

Rainfall and temperature influence agriculture and vary from region to region.

Agriculture Throughout the Regions

Areas with a lot of rainfall, such as tropical rainforests, often fall victim to leaching.

Many farmers there use ‘swidden’ agriculture- in which the farmer cultivates a certain plot for a year or two and then abandons it for another plot and lets the forest grow back there.

Swidden Agriculture