The Effect of Crop Rotation and Weed Control on the Weed Seed Bank in the Soil

Abstract

Quantitative and qualitative changes in the weed community and the weed seed bank in the soil due to crop rotation and weed control measurement were studied by the UNA  Managua at "Las Mercedes" Experimental Station from 1987 to 1990. A bifactorial  permanent field trial combined five grain crop rotations and three weed management  systems. To detennine the weed seed bank in the soil a modified cultivation method  was used. Results are showing significant differences between crop rotations and weed  control systems after the first three year trial period. The level of weed infestation in  the field (actual) varied from 88 to 440 ind./m², while the weed seed bank in the soil  (potential) was determined from 3125 to 12969 seeds/m², giving emergence rates from  0.5 to 14.2 %. The highest values were registered in the cucumber-soya rotation with  330 ind/m² and 6771 seeds/m². The chemical weed control with 227 ind./m² and 6062  seeds/ml had a low efficiency due to predominance of tolerate species Rortboellia  cochinchinensis, counting until 405 ind./m². The lowest actual infestation was reached  in the corn-sorghum rotation with 101 ind./m² and the lowest potential in the corn-soybean rotation with 4010 seeds/m². Periodic weed control reduced weed infestation until 109 ind./m² and 3531 seeds/m².