This paper investigates the impact of contour hedgerows on maize yields. The author applies and agricultural production function to assess data from upland Philippine maize farms and hedgerows of double rows of the nitrogen-fixing species Desmodium rensonii and Flemengia macrophylla. Although the findings show a positive long term impact on maize yields, the short term impact of hedgerows is negative; they reduce land available for cultivation and decrease productivity of the maize crops that remain. The hedgerows become a positive use of cultivatable land after approximately eight years.