Precision Liming for Alfalfa Establishment

Dennis Penington and Richard Leep

Barry County Extension Agent and Professor, Department of Crop and Soil Sciences

Michigan State University

Background

Traditional soil sampling techniques involve collecting several cores from each field, mixing the soil and submitting a composite sample that was representative of the whole field.  With the onset of new and developing technology, it has become possible to manage fields on a smaller scale or “site-specific” basis.  With the use of GPS and VRT, the amount of lime and nutrients can be applied at varying amounts within a whole field. A research plot was established at Kellogg Biological Station to compare these two methods of lime application to alfalfa.

Design

Treatment 1 is defined as the whole field approach and labeled “WF”.  This treatment was established by collecting 24 soil samples on a 1-acre grid using GPS.  These samples were sent to the lab and analyzed.  The average soil pH for all 24 points was used to determine the lime recommendation for treatment 1.  The average soil pH for the field was 5.8, resulting in an application rate of 1.45 tons/acre.

Treatment 2 is defined as the site-specific approach and labeled “SS”.  This treatment was determined by one soil sample taken at one grid point.  Plots 20 foot by 50 foot were established with point 13 as the central location of the plots, as described in the picture below.   The soil pH at point 13 was 5.5, resulting in an application rate of 2.0 tons/acre.

The research plot layout is a generalized, randomized complete block design with 4 blocks and two replications per block.  Randomization was accomplished using Proc Plan in SAS. Yield data and stem counts collected on each plot and is reported in the table below.  Proc GLM was used to produce the ANOVA table and analyze the data. The results are shown in Table 2.

Data

Treatment	Soil pH	Lime (tons/acre)	Yield (g)	Stem (per sq. ft.)
1 (WF)	5.8	1.45	285.7	129
2 (SS)	5.5	2.0	289.9	143
ANOVA (p-value)			0.701	0.538

Results and Discussion

There was no significant difference in yield between treatment 1 and 2.  This is a reasonable conclusion due to the fact that lime was applied in November 1999.  It takes lime up to 18 months to fully activate and adjust soil pH.  It is expected that we will see more significant yield differences next year.  It is also important to note that the WF and SS soil pH were only 0.2 points different, which means that the recommended amount of lime to raise pH to 6.8 was nearly the same.

There appears to be some differences in stem count between treatments.  However, with a p-value at 0.538, there is no statistical significance.  The reason there is no significance is because there are not enough degrees of freedom or sample points.  Stem counts will be taken again next year, which will double the degrees of freedom and should impart significance to this test.  Stem count is important to consider in an alfalfa crop because stand persistence and longevity is important.  It is too costly to re-seed every year.  The longer you can keep a stand productive, the more profitable it will be.