DERIVATION OF PLANT GROWTH COEFFICIENTS FOR THE USE IN WIND EROSION MODELS IN ARGENTINA

MENDEZ, M.J,; BUSCHIAZZO, D. E.

SOIL SCIENCE

LIPPINCOTT WILLIAMS & WILKINS

Lugar: Philadelphia; Año: 2008 vol. 173 p. 368 - 469

0038-075X

Relationships between wind erosion soil loss ratio (SLR, the quotientbetween the soil loss in a ground cover and a bare and smooth soil) andthe percent of soil coverage with plant residues or canopy have beenmostly obtained by means of wind tunnel experiments where fluiddynamic parameters, driven in the nature by climatic conditions, can bemaintained constant. To test the behavior of SLR under natural conditions,we compared wind erosion measured in the field in a semiarid environment of Argentina, during 3 sunf lower (Helianthus annus) and 3 corn (Zeamays) growth periods, with wind erosion calculated with availableequations. Results showed that the relationship between measured SLRand percentage of soil cover with f lat residues fitted well to the alreadyavailable equation SLRf = eja(SC), where SC is the soil cover with flatresidues and a is a constant, but with an a coefficient of 0.0605 instead ofthe originally provided 0.0438. This resulted in an averaged dif ference inthe SLR of 37% between both equations. The variation in SLR wasattributed to differences in the highest speeds used for the derivation ofthe original a coefficient (16 m sj1) than wind speeds occurring duringfield measurements in this study (10.8 m sj1, in average). The relationshipbetween SLR and soil coverage with f lat residues for storms with erosionamounts higher than 100 kg haj1 had an a coefficient of 0.039, very closeto the original a coefficient. Measured SLR as a function of soil cover withcorn and sunflower canopy was quite similar to calculations made withthe previously available equation , where cc is thefraction of soil surface covered with crop canopy. The published equation , where pgca and pgcb are constants and Pd thedays after seeding, was not adequate to explain the evolution of thepercentage of soil cover by the crops. This equation was replacedby , where a, b, and c are constants and x is the daysafter seeding. SLR calculated on the basis of field measurements was, as afunction of the days after corn seeding, lower than SLR calculated withavailable equations at early-crop growth stages and higher at late-cropgrowth stages. At early-crop growth stages, a critical period for winderosion occurrence due to the low soil coverage with plants, sunflowerhad a better wind erosion control efficiency than corn. Sunflower alsoincreased its wind erosion control efficiency with favorable climaticconditions, whereas corn efficiency remained unchanged. Such differences were attributed to the canopy leaf arrangement of each crop(planophyles in sunflower and erectophyles in corn), which resulted in amore ef fective reduction of wind speed by sunflower leaves than by thenarrow leaves of the corn at same growth stages. On the other hand,sunflower had a more ef ficient use of the solar radiation and a fastercanopy growth. We conclude that the equations developed here for use inempirical wind erosion prediction models produce reliable results, even under variable climatic conditions. Such models are useful for sites likethe semiarid Pampas, where detailed climatic information is lacking.