Nemaplot hyperspectral data analysis and population modellingEvaluation reinvented

 

Modeling and density estimation of Heterodera schachtii populations

Damage beet cyst nematode
Field symptoms of H. schachtii
Growth reduction by H. schachtii
Heterodera schachtii Cysts, eggs, Juveniles
Sugar beet canopies with BCN

Choice of crop rotation, a parsimonious difference equation

Formerly a Java applet for online applications have been placed at this position. The security demands of Java or browsers of today are so strict, the applet does not even run on my own computer anymore. Alternatively, we produced the results graphically for all combinations available and provide the basic backgrounds.

The model predicts the long term dynamics of BCN Heterodera schachtii on a discrete year axis. An initial value of the population Pi is required. The following difference equation difference equation calculates the population size at year n+1 as a function of the Pi value at year n, the number of generations and the type of cultured crop. This autumn value is reduced by a constant overwintering rate pov (= 0.6) determining the target size eggs & juveniles/100 ml soil for the next spring. The population decreases under the chosen non-host of the crop rotation with certain probabilities, and finally results in a Pi value at pre-planting next time sugar beet. The objectives are to keep the population density of BCN below the threshold level of 500 E&J/100 ml soil at planting sugar beet. The threshold value must not be seen that strict anymore, depending how much risk you take, up to ~800-900 E&J might be tolerable. The model predicts the population for each spring, or pre-planting sugar beet. A Pi value above the threshold provides a rough estimate about the losses to be expected (approx. 1% per 100 E&J). The numbers of generations per season is another rough approximation to the temperature conditions of a season (see table) and controls the multiplication rate under sugar beet (for this model only)


Table 1
Generation Climate
1 cold
2 standard
3 warm
4 very warm
5 nowadays possible ?

Small insertion:

The overall population range or theoretical model boundaries generated by the choice of generations and size of crop rotation are shown under the following Link forward


The model shown here performs poor for mostly sandy soil and crop rotations with high proportions of summer cereals. The multiplication rates found in data from those conditions cannot be repeated by the model, a possible reason might not be model but data related, as a mixing with Heterodera avenae might have occurred.

the following abbreviations of parameterised crops are used: SB: sugar beet; WW: winter wheat; WB: winter barley; RA: rape; BE: beans; OAT:oat; RYE: rye; MA: maize; PO: potato; SG: summer barley; SW: summer wheat;
The following intercropping species are implemented: (RA): rape; (MU); mustard; (OIL): oil radish; PH: Phacelia; mustard and oil raddish as resistant varieties, rape in short time culture (ca.for 6 weeks).

Heterodera schachtii dynamics
33% SB crop rotation with data from 1971-1994, observations at pre-planting sugar beet only
Heterodera schachtii dynamics
33% SB crop rotation with intercropping, 1971-1986, observations at pre-planting sugar beet only
Heterodera schachtii dynamics
33% SB crop rotation with 2x intercropping 1971-1986, observation at pre-planting sugar beet only
Heterodera schachtii dynamics
SB-WW-WB with resistant Mustard as intercrop
Heterodera schachtii dynamics
SB-WW-WB with Oil raddish as intercrop
Heterodera schachtii dynamics
SB-WW-WG als crop rotation from 1968
Heterodera schachtii dynamics
A 50% rotation SB-WW from 1977-1993
Heterodera schachtii dynamics
SB-WW with intercropping from 1976-1993
Heterodera schachtii dynamics
SB-WW-summer barley from 1977-1993
Heterodera schachtii dynamics
SB-WW-rye from 1976-1994
Heterodera schachtii dynamics
33% rotation with SB-potato-WW
Heterodera schachtii dynamics
25% rotation with SB-WW-summer barley-oat
data show an increasing population under non-hosts
Heterodera schachtii dynamics
33% rotation SB-Maize-WW from 1976-1993
Heterodera schachtii dynamics
25% rotation SB-WW-WW-summer barley
data below detection threshold
Heterodera schachtii dynamics
20% rotation with SB-WW-Maize-Oat-WW
data below detection threshold
back Back to Introduction Continue to decision making by optimisingcrop rotations forward



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