Commodities: Fieldcrops: Peanuts: 2008 Peanut Update

2008 Peanut Update

Tillage and Row Pattern Update

R. Scott Tubbs

Tillage

Conservation tillage (synonymous with strip-till) has not been as readily adopted in peanut as it has in many other crops.  There are benefits that can be gained from turning the soil – physical weed control of emerged seedlings, incorporation of PRE yellow herbicides for supplemental control of weeds, warming the seedbed for quicker crop germination, and so on.  However, it can likewise have some negative impacts like soil erosion, new weed seed brought to the soil surface, and incorporation of cover crops.  By not leaving cover crops on the surface, they will not serve as a mulch to shade weeds and slow the evaporation of water from the soil.  In addition, conventional tillage is costly in comparison to strip-till because of increased energy and time demands to pull implements through the field.  With the price of fuel above $3.00 per gallon currently, each pass through the field is an expensive endeavor.  If the same outputs can be achieved with fewer inputs, then the producer and environmental sustainability will both benefit.

Strip-till is becoming a popular management practice because it combines the benefits of tillage and no-till.  No-till management for peanut does not typically yield as well as strip-till or conventional tillage (Table 1) because of reduced germination due to a cooler seedbed and poor seed-soil contact.  In strip-till, the benefits of tillage occur directly where they will help peanut the most – within the planting row.  Then the benefits of no-till still affect the row middles by suppressing weeds and retaining soil moisture.  This gives peanut a competitive advantage over weeds.

Table 1.  Yield comparison of tillage methods – Hort. Hill, Tifton, GA.

There has been some conflicting reports with regards to peanut yields in conventional versus strip-till management.  That is why it is important to take more than simply yield alone into consideration when determining the tillage system that works best.  In years with adequate rainfall, there is usually no difference in yields between conventional and strip-till.  However, in dry years, strip-till peanuts will often yield more than conventionally grown peanuts.  This is primarily with respect to the slower evaporation of soil moisture thanks to the presence of the cover crop.  The data below (Table 2) shows a yield reversal between treatments in the last two years.  The best explanation for the drop in yield in strip-till for 2007 is because of less control of annual grass weeds that were in competition with the crop for light, nutrients, and water.

Table 2.  Yield comparison of tillage methods – RDC Pivot, Tifton, GA.

Another important factor to consider when selecting a tillage practice, aside from just yield, is incidence of pests.  Tomato spotted wilt virus (TSWV) is often reduced in strip-till compared to conventional tillage.  When cover crop residue stays on the soil surface, it impacts the feeding habits of thrips, which transmit TSWV to peanuts.  Naturally, less feeding by thrips on peanut foliage will typically translate to less damage from TSWV.  There was not a statistical difference in TSWV rating in these experiments (Table 3), but other data have proven reduced TSWV incidence in strip-till management.  Since there is presently no in-season control for TSWV, growers should take every precaution to minimize the possibility of TSWV occurrence.   

Table 3.  TSWV rating comparison of tillage methods – RDC Pivot, Tifton, GA.

Row Pattern

Like with tillage, there is more to take into account than just yield when deciding on row pattern.  The most recent data on row pattern from Tifton Campus has consistently shown no differences in yields between single row and twin row patterns (Table 4).  However, there was a significant difference in TSWV hits in 2005.  Although that difference was not enough to cause a reduction in yield in this study (which was averaged over 8 cultivars), it could be a significant factor with cultivars that do not have a strong disease resistance package, or in very hot and humid years where heavy disease pressure could totally decimate the peanut crop.  Twin row patterns have also demonstrated the ability to reduce white mold since there is greater spacing between individual plants, slowing the spread of the disease.  There are 3 seed per foot per twin row at planting compared to 6 seed per foot in a single row (same plant population regardless of row pattern, but plants have more space between adjacent plants in twin rows).

Table 4.  Yield comparison of row patterns – RDC Pivot, Tifton, GA.

Table 5.  TSWV rating comparison of row patterns – RDC Pivot, Tifton, GA.

Therefore, because of the potential to reduce pest problems, which could occasionally lead to yield increases, conservation tillage and twin row patterns are recommended practices by the University of Georgia for peanut production, unless specific circumstances warrant the use of other techniques.

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