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Reporting
Period:
September 1, 1999 to August 31, 2000
Objectives:
1. Determine
variation in soil moisture in peanut fields
2. Relate
peanut pod rot or other diseases to soil moisture
3. Develop
recommendations to treat peanut for pod rot based on soil moisture.
4.
(Not stated in original proposal) determine the relationship between
peanut foliar
browning (unknown cause) and site-specific factors in the field.
A. Summary
of Progress:
1) Soil
moisture was measured across the Western Peanut Growers circle during
July - September. During much of July, a Thetaprobe and MSTR probe,
which are tools that would be readily accessible to producers were used.
From late July through middle of September, neutron probe readings were
taken at 89 locations within the peanut part of the circle, and approximately
90 locations in the cotton part of the circle. Only the readings for
the peanut part of the circle will be used in evaluations. Soil moisture
was not uniform across the circle as can be seen with Fig. 1 of two
of the evaluation periods at 30 and 61 cm depths. Readings were taken
down to 90 cm, but differed little from the 61 cm depth. A soil moisture
release curve was developed to relate neutron probe readings to % moisture
(gravimetric) and then to pressure. This curve shows an usually steep
decline in moisture with very small changes in pressure (Fig. 2) for
this site.
The Thetaprobe, which only measures surface water, was more reliable
in laboratory testing to relate readings to % moisture than the MSTR
probe, and will be the instrument utilized during the 2001 growing season
in a producer's field. Aerial color infrared photographs were taken
at three times during the growing season. These images can show soil
texture differences and water stress in many fields. However, for the
test circle, soil texture appeared similar across the circle in June
(Fig. 3). There appeared to be an area with slightly different soil
texture in the photograph taken in August (Fig. 4). An image taken in
September (Fig. 5) did demonstrate differences in plant growth that
may be related to water treatments and a foliar necrosis problem which
is discussed later. 
Figure 2.
  
2) The
peanut acreage at the Western Peanut Grower's circle near Denver City
had low levels of Pythium pod rot at various locations (Fig. 6). Each
point in the map is a spot where at least two pods were found with Pythium
like symptoms, but there were no spots found with more than 5 pods rotted
(out of 100's), so no locations were identified with more than low levels
of disease. The soil moisture readings were converted to bars for the
peanut acreage and then a map was created through ARCVIEW surface analysis
extension to predict soil pressure for the entire peanut area (Fig.
6). The points where soil moisture was measured are marked in black
and the spots with pod rot are marked in red (Fig. 6). For each date
that neutron probe readings were taken (27 July, 2 August, 12 August,
16 August, 25 August, 5 September, and 14 September), the area in the
peanut acreage that was 0 to -0.1 bars; -0.101 to -0.20 bars; -0.201
to -0.30 bars; -0.301 to -0.40 bars; -0.401 to -0.60 bars; and -0.601
to -1.1 bars was calculated. The percent of pod rot (out of the total
number of pod rot locations) that occurred in each of these soil moisture
pressure categories was also calculated. The percent of pod rot measurements
was generally similar to the percentage of area each soil moisture pressure
class covered (Table 1). However, on 25 August, the 0 to -0.1 category
accounted for 30 % of the peanut acreage and 48 % of the pod rot spots.
This was the only time period when this wettest category of soil had
more than 3 % of the overall peanut acreage.
3) The
overall goal of this project is to improve the profitability of fungicide
management for pod rot. The fungicide metalaxyl (Ridomil) is the most
common fungicide recommended for control of Pythium pod rot. Pod rots
can also be caused by other fungi in Texas, with Rhizoctonia solani
being the most common problem in the High Plains of Texas. To reduce
the acreage treated with one or more fungicides (if both Pythium and
R. solani are present) it was necessary to develop a variable rate application
system capable of putting out several different combinations of materials
or rates. Dr. Steve Searcy oversaw the development of a variable rate
applicator (Fig. 7). A variable rate sprayer with a direct injection
pump (precision peristaltic injection pump), carrier pump, and control
valves that meter the carrier and active ingredient were provided by
Dr. Searcy as well as a Mid-Tech 6300 Total Application Sprayer Control
(TASC). The Mid-Tech TASC 6300 console controls desired rates by sensing
changes in ground speed or active boom width and adjusting the rate
of carrier and injection of chemical into the carrier accordingly. The
components of a TASC system are radar, flow meter, flow control valve,
boom interface, chemical injection pump, chemical container, and TASC
control console. A WAG vision system is the "brain" that provides
application rates to the TASC 6300. The project purchased a VCD from
WAG Corp., but it is still awaiting delivery. Dr. Steve Searcy provided
a WAG VCD so the system could be tested. The testing was conducted at
College Station as part of a student's (Chris Hundley) precision agriculture
project. The Wag unit reads data from a prescription file, and based
on the location of the sprayer in the field, identification of the proper
application rates for that location are determined and sent to the TASC
console to be executed. A differential global positioning receiver is
used to determine location within a field. The target application rates
for a specific location in the field are sent through a serial port
to the variable rate control interface (VRCI) which then exit the VRCI
and enter the TASC console. The actual rates applied are sent from the
TASC back through the VRCI to the WAG unit and are displayed as an "applied"
field. An overview of the application apparatus is seen in Fig. 8, and
the components for the variable rate system are in Fig. 9. The field
area boundaries are developed through a software package called PC-GPS
(Microtechnology, Corvallis, OR), and then exported as a shape file
to SSToolBox. This software package is used to create the application
map. The system tested in College Station included carrier and active
ingredient (ai) rate parameters. In the tests (Fig. 10), where the carrier
was designated as 0 or ai as 0, the system should have been off (grey
areas), and when the carrier was 15 (blue areas) and ai > 0 (red
areas) the system should have been on. For the most part this did occur,
though in the northwestern most blue square, the system turned off partway
through (Fig. 10). In a second test, the system failed to turn off in
one grid (northwest most grid) and the rates applied were slightly higher
than desired for one pass (western grid in red, in the middle) (Fig.
11). The system will be operating at the Western Peanut Grower's circle
during 2001 and will need more testing as to reliability. For the 2001
growing season, fungicide applications will be made based on the area
in which the soil is near saturation (0 to -0.1 bar).
4) A light colored browning symptom has plagued peanuts grown in the
west Texas area. Often large parts of a field will die prematurely,
with the primary symptom being leaf edge burning which quickly progresses
to all above ground parts. Though a number of People have investigated
causal agents (Thielaviopsis basicola, and salt concentrations), no
satisfactory explanation has been found. The Western Peanut Grower's
circle demonstrated this problem during the 2000 growing season during
September. A map was created based on the intensity of symptoms (Fig.
12), and soil samples were taken from a number of locations, which were
georeferenced, and analyzed for conductivity of the 0-3" and 4-6"
depths. The intensity of symptoms was negatively related to salt concentration
in the soil, but salt levels did not exceed levels damaging to peanut
(Table 2). However, the pattern of browning was related to the irrigation
treatments. Those receiving LEPA did not show browning symptoms and
those in a "spray mode" showed the most severe symptoms. The
irrigation systems which applied the same amount of water as the LEPA
and spray systems, but were intermediate in the type of application
(i.e. not as concentrated an amount of water as LEPA or as much a droplet
as the spray mode) showed symptoms closer to the severity of the spray
mode than the LEPA system. The amount of water was varied within some
of the LEPA treatments, however, that did not appear to be related to
the browning symptom. So, the "cure" for the browning symptom
was discovered (i.e. use LEPA), but the causal agent is still unknown.
It does appear that efforts should be concentrated on the above ground
plant instead of soil factors.
B. Education/technology
transfer:
Since this work is preliminary, it has not yet been shared with others
outside of the project. All the data collected will be rechecked for
errors during the winter, before a firm conclusion will be reached.
The peanut field season only terminated a week prior to this report
being due, so the analysis is preliminary. Using remote sensing to detect
soil texture changes however has been well documented in previous projects.
Two sessions were used to present remote sensing information to county
agents and producers during a precision agriculture meeting held in
Ropesville, TX in August. Participants included T. Wheeler, H. Kaufman,
and S. Searcy.
As a response to the meeting with the precision agriculture committee
during the past summer, Harold Kaufman flew fields for 11 producers
who were working with Scott Orr, Water Use, Conservation and Compliance
Director with the High Plains Underground Water District #1. Terry Wheeler
processed the images into vigor classes so the producers could more
easily interpret the images. There has been no feed back from Scott
Orr as to the response of the producers to the images.
C. Milestones
achieved: Pod rot, though minor during 2000, was spatially correlated
with near saturated conditions in the field in late August.
D. Publications:
None have yet been produced based on this project, though precision
agriculture type publications are listed on other projects (see Bronson
for on-farm research (Wheeler and Kaufman), and Lascano for the research
cotton project (Searcy).
E. Precision
agriculture proposals:
Testing the reliability of remote sensing directed scouting for integrated
pest management, submitted to the Southern Regional IPM program, by
Wheeler, Kaufman, and K. Siders.
Comparison
of conventional IPM scouting versus remote sensing directed IPM scouting.
K. Siders, T. Wheeler, and H. Kaufman. Funded for $15,000 from 1/00
- 12/00. This project has been resubmitted to Texas Dept. of Agriculture
for the 2001 growing season.
F. Precision
Agriculture meetings attended/papers presented: none at precision
agriculture meetings, however, precision agriculture presentations are
listed below for 1999 - 2000.
12/6/00:
Remote Sensing, A Practical Diagnostic Tool for Cotton Problems, 2000
Plant Protection Conference, College Station, TX. Kaufman
9/20/00:
Precision Agriculture, presented in Saltillo, Mexico, as a keynote speaker
for an agricultural symposium. Wheeler
8/14/00:
Can Remote Sensing be used to create Variable Rate Nematicide Application
Maps?, American Phytopathology Society Annual Meeting, New Orleans,
LA. Wheeler
1/8-9/00:
Remote Sensing and Agriculture (poster, joint with representatives from
Mississippi State, Utah, and Penn State), Farm Bureau National Meeting,
Houston, TX. Wheeler
1/7/00:
The relationship between incidence of Verticillium wilt and reflectance
in a wilt nursery, National Cotton Annual meeting, San Antonio, TX.
Wheeler
G. Other developments:
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