Soil Sampling and Testing
Soil sampling and testing are essential to determine soil properties and fertility levels to make good management decisions about fertilizer, manure, and lime application rates.
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- [00:00:00.599]This is Amy Timmerman with Nebraska
Extension and this weeks’ Ag Update.
- [00:00:05.655]Soil sampling and testing
are essential to determine
- [00:00:08.735]soil properties and fertility levels
to make good management
- [00:00:12.205]decisions about fertilizer, manure,
and lime application rates.
- [00:00:16.563]Appropriate nutrient and amendment
applications can increase crop yield,
- [00:00:21.152]reduce input cost, and
minimize environmental impact.
- [00:00:25.040]Soil testing becomes inexpensive
when compared to the total
- [00:00:28.800]investment in
crops and fertilizers.
- [00:00:31.530]Soils are typically sampled
in the fall or spring.
- [00:00:34.702]Either time works to determine
- [00:00:38.702]sulfur, micronutrient and
- [00:00:42.400]However, if trends in nutrient
concentrations are being
- [00:00:45.410]compared over time, it is
important to sample at
- [00:00:48.700]similar times of the year.
- [00:00:50.510]For nitrogen recommendations,
it’s recommended that both
- [00:00:54.058]soil organic matter and
residual soil nitrate-N be measured.
- [00:00:58.936]The timing of soil sampling for
making Nitrogen recommendations
- [00:01:02.689]could be important as snowmelt and
precipitation during early spring
- [00:01:07.389]may affect Nitrogen losses
(especially for coarse-textured soils),
- [00:01:11.768]resulting in under application of
pre-plant or in-season Nitrogen.
- [00:01:16.387]Collecting pre-plant soil
nitrate-N soil samples to
- [00:01:20.167]a two- or three-foot depth
is a good practice for determining
- [00:01:24.755]residual soil nitrate-Nitrogen to be
credited in Nitrogen rate decisions.
- [00:01:30.048]A critical step for successful
soil sampling is to collect
- [00:01:34.048]representative samples
from the field.
- [00:01:36.530]The University of Nebraska
provides detailed information
- [00:01:39.552]about different approaches
for soil sampling for
- [00:01:42.252]uniform and variable-rate
- [00:01:46.082]More information can
be found by googling
- [00:01:48.632]Nebraska’s Guidelines for Soil
Sampling, NebGuide 1740.
- [00:01:53.871]The sampling pattern should be
selected based on the nutrient
- [00:01:57.251]management decision needing to
be made and to best represent the field.
- [00:02:02.385]For uniform fertilizer applications,
samples can be collected randomly
- [00:02:07.295]within representative
areas of the field.
- [00:02:09.775]However, accounting for known sources
of variability in soil fertility such as
- [00:02:14.841]soil types, cropping history and
erosion, is still helpful in adjusting
- [00:02:20.211]recommendations even if the
fertilizer is uniformly applied.
- [00:02:24.211]Consider grid sampling
of one to 2.5 acres
- [00:02:27.401]if soil type or previous
managment such as differences in
- [00:02:31.401]in livestock containment, manure
application, irrigation amounts
- [00:02:36.048]or cropping history causes
variation in nutrient availabilities.
- [00:02:40.817]Consider zone or directed
sampling if yield maps,
- [00:02:45.487]remotely sensed images or other
sources of spatial information
- [00:02:48.827]are available and show consistency
from one layer to another layer.
- [00:02:53.677]Both grid and directed soil sampling are
valid options for precision soil sampling.
- [00:02:58.815]Grid sampling for nitrate-N
is not recommended because
- [00:03:02.455]annual fluctuations in
nitrate levels would require
- [00:03:06.185]annual grid sampling,
which is not cost-effective.
- [00:03:09.176]Instead, residual nitrate sampling
(to a depth of three feet)
- [00:03:13.226]should be done on a
directed sampling basis.
- [00:03:16.896]Sampling depth is another key
factor for good sampling.
- [00:03:20.460]It is important to represent
the root zone where the
- [00:03:23.300]plant will uptake nutrients,
but it must be consistent
- [00:03:26.230]with the sampling depth
used in developing the
- [00:03:28.556]calibration data set to be used
for interpreting the soil tests.
- [00:03:33.046]In dry years, when it is difficult
to push the probe into the ground,
- [00:03:36.366]there is a danger of not
getting the proper depth.
- [00:03:39.456]Sampling too shallow will often lead
to unusually high soil test results
- [00:03:44.179]because of the tendency for nutrients
to become concentrated near the surface.
- [00:03:48.586]Shallow sampling will thus overestimate
the actual soil nutrient status
- [00:03:53.269]and lead to underestimating
fertilizer rates needed.
- [00:03:57.269]Soil samples for determining soil pH,
soil organic matter, and availability
- [00:04:03.109]of any nutrient other than N should
be taken from the 0-8 inch soil depth.
- [00:04:08.957]A single sample should be
comprised of thoroughly
- [00:04:12.520]mixed soil from 12 or more
places in the sampling zone.
- [00:04:16.520]Sampling zones should
be 40 acres or less.
- [00:04:19.362]Guidelines for interpreting
soil test results for nutrient
- [00:04:23.302]application decisions are
available in crop-specific
- [00:04:26.362]UNL Extension publications
and in the Extension book,
- [00:04:29.452]Nutrient Management for
Agronomic Crops of Nebraska.
- [00:04:33.502]Or reach out to your local
extension office for assistance.
- [00:04:36.715]This has been Amy Timmerman
with Nebraska Extension.
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