Download Lecture Notes on Cropping Systems - Principles of Weed Science | AGRON 317 and more Study notes Agricultural engineering in PDF only on Docsity! Principles of Weed Science Agronomy 317 Cropping Systems I. Crop rotation โ a planned order, or sequence, of different crops in the same field A. Benefits of crop rotations (other than weed management) 1. Nutrient management โ include legumes for nitrogen fixation 2. Disease and insect management โ most corn rootworms egg only overwinter a single year, so rotating to soybean eliminates eggs since soybeans canโt act as a host and the larvae die. Many diseases overwinter on crop residue, rotating reduces inoculum level. 3. Soil health โ crops have different rooting patterns, amounts of residue retuned to soil, potential for erosion, etc. 4. Diversification โ crops adapted to different environment, some will not be affected as badly as others by unfavorable growing condition, markets, etc. B. Benefits of crop rotations in managing weeds 1. Weeds prefer crops with similar life cycles a. Summer annual weeds dominate summer annual crops (foxtail in corn), perennial weeds dominate perennial crops b. If similar crops planted continuously, density of weeds adapted to those crops increase over time c. Diverse rotations may have more total weeds, but increase is due to a greater diversity in weed species. It is better (easier to control) to have a weed community composed of many species with none that dominates the population, rather than a weed community dominated by one or two species 2. Crop competitiveness a. Crops vary widely in competitiveness โ including highly competitive crops in a rotation enhances suppression of weeds b. Factors influencing competitiveness of a crop i) Growth habit ii) Row spacing iii) Plant density 3. Different management tactics used in different crops โ reduces ability of weeds to adapt to control strategies a) Mowing โ forage crops b) Mechanical control used in crops planted in wide rows (corn, soybean) i. cultivation ii. rotary hoeing, harrowing c) Herbicides d) Crop canopy โ portion of season where full canopy is present C. Weed suppressive rotations typically include: 1. Crops planted in wide row spacings โ mechanical, chemical control 2. Crops planted in narrow rows โ suppressive crop canopy 3. Forage crops โ mowing 4. Crops with different life cycles - different planting, harvest dates, crop canopy at different times of year
