German farmers were in a unique position in the Nazi dogma because of their relationship to the Nazi ideology of "blood and soil". At its most basic idea "blood and soil" was the belief that German's pure Arian past was maintained by the unspoiled heritage of the German farming peasant.
This belief would impact German farmers especially women in several ways. First: during the war because the Nazis desired farm women to be keepers of the household and limit their work in the fields, they reverted their role in the 20th century farmstead back to a bygone era that didn't fit with the demands of modern farm production and greatly impacted food production during the war. Second: farm women were encourage to wear and make dirndls as they were a symbol of unspoiled "true" German clothing, however the dirndl is very restrictive and dress not meant to be worn in the fields meaning that many women didn't follow the Nazi rhetoric on this front. Third: traditional inheritance laws were re-establish meaning that German women could no longer gain full inheritance of a farm stead on the passing of their husband, this follows suit with other male centric beliefs of the Nazis, but also shows Nazi attempts to revert the peasant traditions to what they considered a more "pure" form.
To sum it up during the existence Nazi Germany farmers were given a new role as carriers of pure German culture yet in many ways the ideas the Nazis had about the German peasants were from a mythic past that no longer existed. Meaning that farmers were more shaped by, rather than embodied the ideals the Nazis wanted them to possess.
[source one by Dagmar Reese]http://www.press.umich.edu/180957/growing_up_female_in_nazi_germany [source two by Irene Guenther]http://books.google.ca/books/about/Nazi_Chic.html?id=NTlXQff8n94C&redir_esc=y
Of course individual farmer's cases are nearly impossible to tell, but I can quickly tell you how the state of agriculture in WW2 Germany changed.
First of all, going along with /u/DropDeadGravy's unique role of German farmers, the NSDAP also placed emphasis on scientific management. After the NSDAP took power, they began making vocational education available for farmers. As opposed to handing down knowledge or working, agricultural skills were taught to be regimented and made the most efficient, as well as government instruction and quotas on which breeds of livestock needed to be bred.
The use of machinery on farms doubled under the NSDAP as well, and those machines were standardized fully, allowing repairs and part replacement to be easy and inexpensive.
So pre-war agriculture lost much of its individuality, and this continued through the war to fill the stomachs of the German people. Now during the war, the number of native farmers dwindled, as 37.6% of Germans were fully mobilized by 1943. To make up for this, the Germans used POWs or civilians from occupied territories to bolster the workforce. In 1943, there was an (estimated) six million foreign laborers and in Germany (2 million of them were women), and two million POW laborers, but the majority (nearly 65%) went into industry and labor.
A short answer is that after the start of WW2, many farmers stopped farming and joined the Wehrmacht, their labor replaced with foreigners.
Sources:
Harding, T. Swann, "Food, Agriculture, and the War"
Harrison, Mark "Resource Mobilization for World War II: The U.S.A., U.K., U.S.S.R., and Germany, 1938-1945"
Spoerer, Mark and Jochen Fleischhacker "Forced Laborers in Nazi Germany"