Weeds in Crop and Soil Science: Definition, Impact, Control and Classification, Study notes of Agricultural engineering

Download Weeds in Crop and Soil Science: Definition, Impact, Control and Classification and more Study notes Agricultural engineering in PDF only on Docsity! AGA 105 Crop and Soil Science Chapter 15: Weeds • Definition: Plant out of Place • Losses: 42% of Costs of all Pests • Competition Results in 17% Yield Losses in Soybeans, 10% in Corn • “Control not Eradication” Harmful Effects • Decrease Land Value • Lower Crop Quality - not Pure • Decrease Yield – Weeds Are Fierce Competitors • Harbor Insects and Diseases • Increase Irrigation Costs • Injure Livestock – Barbs, other Structures – Poisons Poison Weeds • High Nitrates – Interfere with Oxygen Transport by Blood – Death can Occur – Pigweed, Lambsquarters • Prussic Acid – Will Convert to Hydrocyanide when Eaten by Ruminants • Wild Cherry • Johnson Grass Characteristics • Quantity of Seed – Rough Pigweed – 200,000 Seeds per Plant – Mullein – 225,000 • Dormant Seeds (Alive but not Germinating even when ‘Growth Factors’ Were Present) 1 • % Alive after 40 yrs. – Jimsonweed 91% – Lambsquarters 7% Classifications • Life Cycles – Annuals • Easier to Kill than Biennials or Perennials but Harder to Control – Thousands of Seeds can Survive for Years in the Soil – Transported by Wind, Water, Animals, Machinery • Most Common Weeds Are Annuals – Biennials and Perennials • Harder to Kill than Annuals • Extensive Underground Storage and Reproductive Organs • Broadleaf vs Grasses • Physiological Differences Affect Herbicide Toxicity • 2,4-D Toxic to Broadleaves • Dicot vs Monocot Illegal Weeds • Can not Grow! • State Dependent Prohibited Noxious Weeds • Unlawful to Be in Seed that Is Sold – eg: Johnson Grass – Difficult to Control due to Reproduction from Seeds and Asexual Means and They Are Perennials Restricted Noxious Weeds • The Number/Pound of Seed must Be Noted on Bag Common Weeds • Must Note the Percent by Weight that Is in the Seed Bag Weed Control • Mechanical – Tillage • Bury Weeds or Weed Seeds • Cuts the Roots of Weeds – Mowing • For Perennials – Repeated will Deplete Root Reserves (Starves) • For Annuals – Prevents from Going to Seed 2