|Fangmeier, Delmar - UNIVERSITY OF AZ, TUCSON|
Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 8, 1999
Publication Date: N/A
Interpretive Summary: Level basin irrigation systems can apply water to crops uniformly and efficiently over large fields. However, the actual performance of a level basin system depends to a large extent on the specific conditions of the field soil at the time of each irrigation. These conditions, such as the soil infiltration rate and the roughness of the soil surface, can often change from one irrigation to the next and can be particularly affected by tractor operations and other forms of management that a farmer uses to grow the crop. We conducted studies with large level basins that enabled us to describe how typical farmer management practices for cotton change the rates at which water infiltrates into the soil and advances across the field during the season. We also showed that the water can advance across the field faster if the furrows in the basin are smoothed with devices attached to the tractor during cultivation activities. For level basins, achieving more rapid water advance is beneficial, since this tends to increase the uniformity of water applied in the field. Knowing how much field conditions change because of farmer practices increases our ability to predict accurately the performance of level basin irrigations. This information will be useful for irrigation designers and consultants to help farmers manage their level basin irrigations more efficiently.
Technical Abstract: Studies were conducted in central Arizona in 1993 and 1994 during two cotton seasons to evaluate the effects of cultural and irrigation management practices on infiltration, soil roughness, and water advance in furrowed level basins. Factors considered included tractor wheel traffic, furrow smoothing, irrigation frequency, basin flow rate, and the effects due to seasonal variations caused by soil cultivation operations. In 1993 five treatments incorporated three variables: irrigation frequency (high or low), furrow smoothing (torpedoed or non-torpedoed furrows), and basin flow rate (moderate or high). In 1994, there were only two treatments: (1) low frequency, non-torpedoed, moderate basin flow rate, and (2) high frequency, torpedoed, moderate basin flow rate. Infiltration was determined during the cotton seasons using the blocked-furrow infiltrometer method. Overall, seasonal variations and tractor wheel compaction were the factors that had the greatest impact on infiltration. However, furrow torpedoing significantly influenced both soil roughness and water advance with the moderate flow rate, where roughness was as much as five times greater and water advance was as much as two times longer for non-torpedoed than torpedoed furrows. However, a higher flow rate tends to overcome the effects of torpedoing on advance. Thus, the most significant benefits of smoothing versus not smoothing furrows were reduced soil surface roughness and faster water advance with the moderate flow rate.