Location: Crop Genetics Research2013 Annual Report
1a. Objectives (from AD-416):
The overall objective is to develop soybean cropping systems that reduce disease and nematode incidence, maximizing yield and economic return.
1b. Approach (from AD-416):
The Tennessee Agricultural Experiment Station (TAES) will use existing and new research plot areas to measure the effects of soybean cropping systems variables, such as no-tillage, cultivar selection, seeding rate, planting date and use of animal waste, on diseases and soybean yield. This will be done on cropping systems experiments already in place at University of Tennessee (UT) and on experiments being conducted by USDA, ARS scientists in the Crop Genetics and Production Research Unit. TAES will provide expertise in possible cropping system changes to enhance economically and enviromentally viable soybean production.
3. Progress Report:
The effects of tilled and no-tilled cropping systems on soil diseases and soybean cyst nematode incidence and severity are being evaluated. Research is underway on a long term soybean experiment comparing single to double-cropped soybeans and winter wheat. The six main plot treatments include tillage (disc only, chisel plow, and moldboard plow) compared to no-tillage (single crop in winter wheat cover, single crop in previous crop residue, and no-tillage after wheat harvest in a double crop system). Each of the six treatments are split with one half being no-tillage soybeans and the other half being tilled. Sampling is underway on all plots to determine nematode populations, and soil bacterial and fungal levels. Charcoal rot incidence and severity is also being monitored. The split plot design was discontinued in 2012 with plots being restored to the original design. Similar data will be collected but will now include bacterial community structure analysis. Different procedures to determine microbial community structure have been used on these plots to determine relationships between diseases and microbe populations as influenced by tillage, cover crop, wheat grain crop and soybean planting timing. New research will involve more precise bacterial population determinations and whether they are gram negative or gram positive. Other research is indicating that this may have affects on nematode bacterial predation. Biological control from bacterial predation is one aspect of management of soybean cyst nematode. Two new commercially available seed treatment nematicides contain gram positive bacteria as the active ingredient. One protects soybean roots and the other contains a parasite of soybean cyst nematode. Two bacterial parasites of soybean cyst nematode have been found in two research plots in Tennessee. One hyperparasite has been identified as Pasteuria nishizawae. The other is currently unidentified and was found in the tilled and no-tilled study area described above. In greenhouse studies, soil samples were collected from pots containing seed treated with a bacterial nematicide and from soil where the seed treatment was not present. The samples were processed for presence of gram positive bacteria using selective media (crystal violet agar). The number of colonies on crystal violet agar was compared to the number of colonies on the same media without crystal violet. Results showed that this technique could detect the presence of the bacterial nematicide in soil samples. This is the first step in detection of Pasteuria nishizawae in soil samples. New work is also being planned on the effects of rotation crop and cover crop on charcoal rot levels. This will be conducted at the Milan Experiment Station in a long term study where soybeans are rotated with cotton and corn and both with grass and legume cover crops established in each rotation each year. Presently the plots are in their second three year cycle of rotations.