Crops and soil

1. Crops and soil Section 2

2. Overview • This section focuses on soil and its role in agriculture. Farming methods that degrade soil and those that preserve or restore soil will be contrasted. The section also explores methods of pest control.

3. Content/Knowledge Objectives • Distinguish between traditional and modern agricultural techniques. • Describe fertile soil. • Describe the need for soil conservation. • Explain the benefits and environmental impacts of pesticide use • Explain what is involved in integrated pest management.

4. Lab Activities • Studying soil samples: soil’s color, texture, moisture content, organic content and consistency. • Lab: Soil Texture and Permeability lab (handout will be given)

5. Real-Life Connections • Find soil survey information of your local area. After studying, report on the soil conditions in your area. What kind of crop do you think will grow well in that particular area. • Report your findings in the form of a journal.

6. Activity: World Farming Methods • Choose a foreign country and then create an online poster about its farming methods. • Create a poster about the dominant types of farming in your native land. • You need to include information about crops planted, farming equipment used, and popular techniques used. Make sure you use visuals to supplement any text. You may then present it to the class

7. Quick LabPreventing Soil Erosion • Obtain three trays, and fill one with sod, (A section of grass-covered surface soil held together by matted roots; turf.), one with topsoil and one with a type of mulch, such as hay. • Place each tray at an angle by creating a surface that resembles a hill by using textbooks. Place a large bowl at the bottom of the tray to catch the runoff. • Sprinkle 2 litres of water slowly to simulate heavy rainfall. • Use the scale to weigh the runoff of soil and water that collected in each. • Analysis: which tray had the most soil erosion and water runoff? Which had the least and why?

8. Agriculture: Traditional and Modern • http://www.youtube.com/watch?v=-Nhz-hIMZng

9. Traditional Farming • The basic processes of farming include plowing, fertilization, irrigation, and pest control. Traditionally plows are pushed by the farmer or pulled by livestock. Plowing helps crops grow by mixing soil nutrients, loosening soil particles, and uprooting weeds. • Organic fertilizers, such as manure, are used to enrich the soil so that plants grow strong and healthy. • Fields are irrigated by water flowing through ditches. • Weeds are removed by hand or machine. These traditional techniques have been used since the earliest days of farming, centuries before tractors and pesticides were invented.

10. Modern methods of Agriculture • Machinery powered by fossil fuels is used to plow the soil and harvest crops. Synthetic chemical fertilizers are now used instead of manure and plant waste to fertilize soil. • A variety of overhead sprinklers and drip system may be used for irrigation and synthetic chemicals are used to kill pests.

11. Fertile Soils • Soil that can support the growth of healthy plants is called fertile soil. Plant roots grow in topsoil, the surface layer of soil, which is usually richer in organic matter than the subsoil is. Fertile topsoil is composed of living organisms, rock particles, water, air, and organic matter, such as dead or decomposing organisms. • Most soil forms when rock is broken down into smaller fragments by wind, water, and chemical weathering.

12. Most soil forms when rock is broken down into smaller fragments by wind, water, and chemical weathering. • Temperature changes and moisture causes rock to crack and break apart, which creates smaller particles. The seeds of plants can fall and take root on these soil particles. It can take hundreds of years for these geological processes to form a few centimeters of soil • Fungi and bacteria live in the soil, and they decompose dead plants as well as organic debris and add more nutrients to the soil. Earthworms, insects, and other small animals help plants grow by breaking up the soil and allowing air and water into it.

13. Soil Horizon • O) Organic matter: Litter layer of plant residues in relatively undecomposed form. • A) Surface soil: Layer of mineral soil with most organic matter accumulation and soil life. This layer eluviates (is depleted of) iron, clay, aluminum, organic compounds, and other soluble constituents. When eluviation is pronounced, a lighter colored "E" subsurface soil horizon is apparent at the base of the "A" horizon. A-horizons may also be the result of a combination of soil bioturbation and surface processes that winnow fine particles from biologically mounded topsoil. In this case, the A-horizon is regarded as a "biomantle". • B) Subsoil: This layer accumulates iron, clay, aluminum and organic compounds, a process referred to as illuviation. • C) Parent rock: Layer of large unbroken rocks. This layer may accumulate the more soluble compounds .

14. Rhizobium

15. Soil Horizon

16. Soil Erosion: A Global Problem • Erosion is the wearing away of rock or soil by wind and water. In United States about half of the original topsoil has been lost to soil erosion in the past 200 years. Without topsoil crops cannot be grown. • Almost all farming methods increase soil erosion.

17. Land Degradation • Land degradation happens when human activity or natural processes damage the land so that it can no longer support the local ecosytem. • In areas with dry climates, desertification can result. • Desertification is the process by which land in and or semiarid areas become more desertlike because of human activity or climatic changes. • Read Desertification in Sahel region and share your thoughts and understanding with your partner. (Page number 386)

18. Dust Bowl • As a result of the Soil Conservation Act passed after the Dust Bowl events, U.S farmers are more likely to use planting and grazing techniques that protect the soil from erosion.

19. 10 ways to Conserve Soil • There are many ways of protecting and managing topsoil and reducing erosion. Soil usually erodes downhill , and many soil conservation methods are designed to prevent downhill erosion • Plant trees: We all know that the roots of trees firmly hold on to the soil. As trees grow tall, they also keep rooting deeper into the soil. As the roots of the trees spread deep into the layers of soil, they contribute to the prevention of soil erosion. Soil that is under a vegetative cover has hardly any chance of getting eroded as the vegetative cover acts as a wind barrier as well.

20. Terraces • Terracing is one of the very good methods of soil conservation. A terrace is a leveled section of a hilly cultivated area. Owing to its unique structure, it prevents the rapid surface runoff of water. Terracing gives the landmass a stepped appearance thus slowing the easy washing down of the soil. Dry stonewalling is a method used to create terraces in which stone structures are created without using mortar for binding.

21. No-till farming: When soil is prepared for farming by ploughing it, the process is known as tiling. No-till farming is a way of growing crops without disturbing it through tillage. The process of tilling is beneficial in mixing fertilizers in the soil, shaping it into rows and preparing a surface for sowing. But the tilling activity can lead to compaction of soil, loss of organic matter in soil and the death of the organisms in soil. No-till farming is a way to prevent the soil from being affected by these adversities.Can you think of the advantages and disadvantages of no till farming?

22. No till farming http://www.ipm.iastate.edu/ipm/icm/2006/5-15/notill.html

23. Contour ploughing: This practice of farming across the slopes takes into account the slope gradient and the elevation of soil across the slope. It is the method of ploughing across the contour lines of a slope. This method helps in slowing the water runoff and prevents the soil from being washed away along the slope. Contour ploughing also helps in the percolation of water into the soil.Crop rotation: Some pathogens tend to build up in soil if the same crops are cultivated consecutively. Continuous cultivation of the same crop also leads to an imbalance in the fertility demands of the soil. To prevent these adverse effects from taking place, crop rotation is practiced. It is a method of growing a series of dissimilar crops in an area sequentially. Crop rotation also helps in the improvement of soil structure and fertility.

24. Contour plowing and Crop Rotation

25. - • Water the soil: We water plants, we water the crops, but do we water the soil? If the answer is negative, it is high time we adopt the method of watering soil as a measure of conserving soil. Watering the soil along with the plants is a way to prevent soil erosion caused by wind.Salinity management: The salinity of soil that is caused by the excessive accumulation of salts, has a negative effect on the metabolism of the crops in soil. Salinity of soil is detrimental to the vegetative life in the soil. The death of vegetation is bound to cause soil erosion. Hence, salinity management is one of the indirect ways to conserve soil.Soil organisms: Organisms like earthworms and others benefiting the soil should be promoted. Earthworms, through aeration of soil, enhance the availability of macronutrients in soil. They also enhance the porosity of soil. The helpful organisms of soil promote its fertility and form an element in the conservation of soil.

26. - • Indigenous Crops: Planting of native crops is known to be beneficial for soil conservation. If non-native plants are grown, the fields should be bordered by indigenous crops to prevent soil erosion and achieve soil conservation. • Use rotational grazing. There is a short grazing period followed by a rest period of longer duration. Grazing is done when the farm is still in the vegetative stage. This prevents crops from being totally eaten away.

27. Proper Soil Irrigation • If topsoil is left dry at the surface, it becomes susceptible to erosion by wind. Ensuring that the land is properly irrigated at the surface can prevent this. Build a Wind Barrier • Although trees provide a partial wind barrier, sometimes they are not enough. Building a barrier or fence at the edge of a farm can stop a large portion of erosion due to wind. Use Organic Mulch • Using organic mulch for crops that are indigenous to the region will maintain the correct soil temperature and prevent erosion.

28. Test the Soil's pH Level • Natural environmental hazards such as acid rain can drastically change the pH level of large areas of soil. Plant life is controlled to a certain extent by this pH level. Maintaining the correct pH level in your soil is vital for conservation. Test the Salinity of the Soil • Just like pH, improper levels of salt can have a negative effect on the metabolism of the plants in the soil. Excessive salinity levels will lead to the death of vegetation, which causes erosion. Test the topsoil annually to ensure it has the correct salinity.

29. Tips to Conserve soil erosion • Use rotational grazing. There is a short grazing period followed by a rest period of longer duration. Grazing is done when the farm is still in the vegetative stage. This prevents crops from being totally eaten away. • Change the plant species on your farm. Don’t use tilling, instead use herbicides to kill the existing plants. • Cover the entire soil with plants, which will significantly reduce erosion. • Along with the plants it’s important to water soil, which keeps it damp and makes it settle down. • Don’t cultivate soils on steep slopes. Do terrace farming. • You can construct wind barriers at the boundaries of the farm. This will prevent wind from blowing away the soil. • Add humus to your soil. It will prevent soil erosion. • Keep grassed waterways to drain out storm water. • To fight storm water, use structures made of natural materials. Use logs or collection of large stones instead of cement and concrete. Natural resources are more effective and inexpensive. • Plant strips of grass, trees or shrubs between water and cropland. It prevents surface movement of fertilizers, pesticides and soil. Strips cause increased runoff of water into soil. There is increased denitrification, in which microbes convert nitrate-nitrogen into gas form that dissipates to the atmosphere. It decreases the amount of nitrate available to move into groundwater and surface water supplies. They absorb nutrients, sediment, and pesticides moving from adjoining cropland before they reach the water sources. The strip’s trees, grass or shrubs absorb the nutrients and pesticides.

30. Enriching the Soil • Soil was traditionally fertilized by adding organic matter, such as manure and leaves, to the soil. As organic matter decomposes, it adds nutrients to the soil and improves the texture of the soil. But this has been replaced by inorganic fertilizers to meet the growing demand of food supply. • If erosion occurs in areas where the soil has been fertilized with inorganic chemicals, fertilizers and pesticides may pollute waterways. • A modern method of enhancing the soil is to use both organic and inorganic fertilizers by adding compost and chemical fertilizers to the soil.

31. Compost • Compost is partly decomposed organic material. Compost comes from many sources. Many cities and industries compost yard waste and crop wastes. This compost is sold to farmers and gardeners, and the process is saving costly landfill space.

32. Salinization • The accumulation of salts in the soil is known as salinization. It is a major problem in places such as California and Arizona. • Salinization can be slowed if irrigation canals are lined to prevent water from seeping into the soil, or if the soil is watered heavily to wash out salts.

33. Reference • Environmental Science By Karen Arms