The J.L. Whitten Plant Materials Center (Coffeeville, MS), with cooperation from the National Agroforestry Center and NRCS Foresters, installed an alley cropping (Conservation Practice 311) demonstration planting in 2002. We were interested in the economic feasibility of planting high-value trees on sloping topography with no-till crops grown in the alleyways between the trees.
An approximately 5 acre field on a hillside with Loring silt loam soil (up to an 8% slope) was chosen as the study site. Site preparation began in the fall of 2001 when 4 qt/ac of Roundup and 3 ton/ac of lime were applied.
Bareroot seedlings were planted in January2002 in single rows along the general contour of the field perpendicular to the dominant slope on angles convenient for farming using CORE4 recommendations. Trees species were pecan (Carya illinoinensis),which can provide income from both nuts and timber, and green ash (Fraxinus pennsylvanica), which is a fairly fast-growing timber species.
|Field trials at the Whitten PMC near Coffeeville, MS test different row crops with pecan trees (Photo courtesy J.L. Whitten PMC))|
Survival of the pecan seedlings (variety "Choctaw")was very poor because the planting stock was too large and lacked necessary feeder roots and stems were damaged by deer (rubs) during the winter. They were replanted in 2003 using better quality stock of "Sumner" and an electric fence was installed around the planting site. Survival was much better; however, additional deer-rubbing from animals that jumped through the fence again caused severe damage to some of the seedlings during the following winter.
We decided that we would not attempt to replace these seedlings with additional pecans. Instead we dug seedlings of yellow poplar (Liriodendron tulipifera) from native stands on the PMC and planted them alongside the most seriously damaged pecans. If any of these pecans survive and make adequate growth, we will remove the yellow poplar; however, if not, it will serve as a replacement. Yellow poplar will not provide the same economic benefits as pecan, but it is a faster growing species and can quickly attain a similar size as the older pecans.
Survival of green ash was good (over 90%), but deer-rubbing resulted in formation of multiple-stem specimens that required pruning to reestablish a central leader. They were pruned in January of 2005.We have planted a variety of crops in the alleyways during the course of the study. Both soybean varieties were Roundup-Ready. The corn, grown in 2004, was not because we were concerned that three continuous growing seasons of glyphosate application on the crops might damage the trees, but it was a BT variety. The crops were fertilized according to soil test recommendations and an additional 2 ton/ac of lime was applied in February2004 when testing indicated it was required. Weed and insect controls were also applied based on normal agronomic practice for each crop.
The soybean yields in 2002 were somewhat low for this variety, but considering this was a new field, converted from sod, they were acceptable. The yields of wheat equaled state averages for this variety. Yields of DP&L 5915RR were slightly lower than the 51 bu/ac recorded for MSU trial locations in the hills, but the soybeans were planted somewhat late since they were double-cropped with wheat. The corn yields were somewhat higher than those reported in variety trials and the reason for this is that we had ample, evenly spaced rainfall during the growing season.
Overall, our yields for all crops have been good because we have had favorable weather, with rainfall when the crops needed it and drier conditions when the grasses were pollinating. Also, the sloping topography of the site created ideal soil drainage. Yields were generally somewhat higher near the bottom of the slope than at the top of the slope because soil conditions improved as you move downhill.
(This article appeared originally in Mid-South Plant News, March 2005.)
By Janet Grabowski
USDA Natural Resources Conservation Service