Forage Production Under Agroforestry Systems

Author: Sam Angima

Publish Date: Fall 2007

One year ago I wrote an article about agroforestry being an option for small scale farmers who may have forestry land that is not is not currently providing any income until harvest time (Figure 1). In 2007, we set up some on-farm forage trials in a thinned forest in Harlan Oregon and gathered forage production data that I want to share with you in this article. In the context of this article, agroforestry is defined as “a land-use system that combines agriculture and forestry technologies to create a more integrated, diverse, productive, profitable, healthy, and sustainable land-use system especially beneficial to the small scale farm”. For basics about agroforestry, visit our website.

Just like most of western Oregon, the farm site where this forage trial is located gets about 50-70 inches of rainfall each year. The soils are classified as Eilertsen silt loams (Finesilty, mixed, mesic Ultic Hapludalfs) with a pH of 5.5, and cation exchange capacity of 15 (NRCS web soil survey). Those familiar with land capability classes, this site has class 2c (c stands for cold climate limitation). The dominant grass species in this site are perennial rye grass, orchard grass and some indigenous species. In winter 2007 we set out some 21 test plots (Figure 2) under two different scenarios. The first nine are set under a thinned 25-year old Douglas fir forest (current tree density about 300 trees to the acre) and the second set of 18 are under 55-year old trees that are ready for harvest and at the same tree density. The remaining 3 plots are the control plots that are set out on a sunny patch that does not get shade. The aim of this setup was to see whether we can still raise some good forage under the trees even under older trees that still provide some light to the understory for forage production.

The grower fertilized this field at the same time he fertilized his other fields in April with 50-75 pounds of nitrogen per acre using urea. Forage was harvested (Figure 3) when the grower indicated he was ready to release his livestock to graze. Therefore this data indicates the actual forage that animals can consume at specific times during the year. Three to four inch stubble was left to support photosynthesis after harvest to allow grass growth. Our first harvest was in May and the second one was in August.

The forage results were a surprise to us (Figure 4). From the soil survey, this area can produce up to 3 tons/acre of hay under full sun with good management. We were able to harvest about 2 tons/acre under the 25 year trees and over 1 ton/acre under the 50 year old trees in two cuttings by August 2007. The control plots growing in sunny areas produced excellent forage at nearly 3.5 tons/acre during the same period. These results are only 2/3 of the year (see Table 1 below) and we expect to harvest one more time before the end of the 2007.

Table 1: Forage harvest (dry basis) under different agroforestry settings in 2007, Harlan, OR.
Site Fertilizer N Applied (lbs/acre) May 2007 harvest (tons/acre) August 2007 harvest (tons/acre) Total forage harvested (tons/acre) Extrapolated for 2007 (tons/acre)
Under 25 yr trees


0.73 1.19 1.92 2.83
Under 55 yr trees 75 0.43 0.63 1.06 1.56
No Trees 75 1.42 2.05 3.47 5.12

From this data, if we took the average year-round stocking rate of livestock for good pasture for Western Oregon of one beef cow to two acres (this is also equivalent to roughly 3-4 sheep per acre), you could essentially, under good management, have half the stocking rate under an agroforestry system of one cow/calf for 4 acres and be able to get some income under maturing forest stands. There are many circumstances that can affect this estimate. These may include your local climate, size of land, topography, investment of time, and of course your local soil conditions. However, what these results are indicating is that utilizing local resources on your farm can get you some income rather than waiting for over 40 years to harvest trees to get income. For more information on using agroforestry systems visit the national agroforestry center website.