Download Life in the Soil - Crop and Soil Science - Lecture Slides and more Slides Botany and Agronomy in PDF only on Docsity! Plant and Animal Life in the Soil Docsity.com What kinds of plants and animals live in the soil? 1) Bacteria: most numerous and important – single celled plants, can reproduce in 20-30 minutes and may decrease rapidly in in favorable conditions – a soil which has 5% O.M. can have 3 1/2 tons of bacteria per acre – crops require free oxygen or aerated conditions in the soil – anaerobic bacteria (do not need free oxygen) get their oxygen from chemical reactions Docsity.com What kinds of plants and animals live in the soil? • 4) Algae: contain chlorophyll – ex: seaweed, scum-forming algae on ponds – soil algae are too small to be seen with the naked eye, but in large numbers can give soil surface a green color – favor damp soil that is exposed to the sun – believed to be able to fix free nitrogen from the air in the soil, valuable to rice production Docsity.com What kinds of plants and animals live in the soil? • 5) Protozoa: minute animals found in the soil, smallest form of animal life – must live in a water film Docsity.com What purpose do microorganisms have? • decay plant residue (straw etc.) • make free nitrogen in the air available to plants • break down nutrients needed by plants • break down cellulose • much of the food in the soil is not available to the plant, until microbes break them down Docsity.com What are false nodules? • insects may injure legumes causing false nodules Docsity.com What is Inoculation? • when a legume plant is grown for the first time, it is essential to expose the seed to Rhizobium bacteria (nitrogen fixing) before planting Docsity.com How much nitrogen is added to the soil by bacteria? • free soil bacteria add 10-50 lbs./yr. • nodule bacteria add 50-100 lbs./yr. • may not be a net gain due to nitrogen in harvested crop • gene splicing may yield a corn plant with nitrogen fixing qualities. This would save the producer money and reduce the need for petroleum (most commercial fertilizers are made from petroleum) Docsity.com What problems result from soil management practices? • conservation tillage reduces microbe activity, thus fertilizer must be added to feed the microbes and speed decomposition (add 20# N/ton of straw) Docsity.com Why do producers summer fallow? • conserve water • conserve nitrogen Docsity.com What are some of the higher forms of animal life in the soil? • slugs & snails: feed on the surface, favor damp shady conditions • arthropods: insects (ants, centipedes) most feed on decaying O.M. • nematodes: (eelworms) abundant in soils, three groups: – 1) feed on plants – 2) feed on other life forms – 3) feed on decaying O.M. (earthworms) up to 500 lbs per acre, aerate soil, allow water to penetrate, excrement is good plant food Docsity.com
