Instead of waiting for the next welfare check, Heino Wittstock is picking asparagus.

The German construction worker has been unemployed for three years. But this spring, he joins some 280,000 Polish migrant farmhands, plucking the foot-high green and white sentinels from the rich Brandenburg loam.

"I need to do something; Sitting at home on the couch is not an option," he says.

In an unusual effort to address its 11.9 percent unemployment rate, Berlin is also trying to answer a common refrain in many industrial nations: "Foreigners are taking jobs away from us."

In Germany, the spring asparagus is harvested by migrant farmworkers. But the labor ministry has a new rule that says 10 percent of seasonal farmworkers should be German.

With only 170 German field hands in the state of Brandenburg so far, the experiment is off to a rocky start. And German farmers are angry, saying native-born pickers are only half as efficient as the Poles.

Unemployed Germans lack both practice and motivation, farmers here say.

"You can't force people into work," says Dietrich Paul, spokesman for asparagus farmers in the state of Lower Saxony, one of Germany's biggest asparagus regions, "especially not this line of work."

Adding to the farmers' concern is the feeling that Germany, already one of the most restricted labor markets for unskilled workers, is putting up hurdles that will push Eastern European workers to increasingly look elsewhere in Europe for work. Germany's enforcement this year of an EU rule requiring Polish migrant workers to pay social security on the wages they earn has already decreased the numbers coming over for the annual harvest, say farmers.

"These seasonal workers are the basis of the biggest farms," says Mr. Paul. "They are the reason ... permanent jobs are created. If less and less come, then the farms will shrink."

Labor ministry officials deny they have anything to do with the decrease in foreign workers. The 10-percent rule introduced this season is about integrating Germans into the agricultural workforce, not trimming foreigners from it. And in contrast to failed attempts to do similar things in the past, the labor ministry is not trying to "force" anyone, says Ulrich Waschki.

Cash on top of a welfare check

Rather, he says, they're trying to recruit volunteer field hands from the ranks of the unemployed who will be attracted by the prospect of earning money on top of their monthly unemployment checks.

Depending on the region, the labor agency will pay German farm workers between 13 and 20 euros ($16.50 - $25.50) a day on top of the hourly wage they receive working on the farm, according to a spokesman. At the end of a month of work, that can mean as much as 480 euros, tax-free, from the labor agency. The additional income appeals to Mr. Wittstock, who has struggled to support his girlfriend's three children from another relationship.

"The children also want things, and we can't afford them [on unemployment] alone," says Wittstock, who gets 298 euros a month in spending money from the government in addition to a housing subsidy.

German officials say that more important than the short-term cash injection is the hope that regular work will give people like Wittstock the psychological boost needed to get back into the regular job market.

"The harvest, at the very least, gives them some perspective," says Dirk Johl, second in command at Agrotime, a private job search agency for the agricultural sector. "And they need that."

Mr. Johl works to place jobless Germans as seasonal workers in Brandenburg's biggest asparagus farms. Before sending them to the farms, he makes sure the Germans understand the strenuous work demanded of them. He even sets up beds of asparagus to train them.

Thanks to the 10- percent rule this year, he's been able to place 170 unemployed Germans at 12 farms in the region, more than in years past. (The harvest just began this month, so no national statistics are available yet.)

An advocate for the jobless, Johl nevertheless is a realist when it comes to his trainees' limits. "The average Polish worker can harvest up to 400 kilograms [881 lbs.] a day of asparagus," he says. The average German, picks about 200 kilograms, he says.

"The Germans get tired quickly. We're happy to work more," says Karolina Pawlak, taking a break from sorting asparagus at a farm not far from where Wittstock was working.

2,000 euros in six weeks

A nurse from the town of Konin, in central Poland, Ms. Pawlak took paid vacation for six weeks from her job and drove some 370 miles to Beelitz to work on the Jakobs Farm. She says she'll earn 2,000 euros during her time at the farm, the equivalent of six months pay at her hospital. "I like to work and I'd like a better life in Poland, so that I'm not just living month to month," she says. With the money she's earned this year and last year, she's building a house.

But German farmers are increasingly concerned reliable workers like Pawlak will move on to more flexible labor markets in the coming years. The EU rule requiring Polish migrant workers to pay up to half of the wages they earn during the two-month asparagus harvest into social security has been in effect since Poland joined the EU in 2004. German and Polish authorities have been trying to reach an understanding that would be more agreeable to migrant workers, but haven't yet.

"Many Poles will no longer come to Germany," predicts Joerg Buschmann, co-owner of Buschmann & Winkelmann, the region's largest asparagus farm. "They will go to Spain, England, or Denmark, where the labor market is a bit loose," meaning the enforcement of the EU social security rule is more lax.

During the harvest season, his farm employs 1,350 people, 800 of them Polish workers picking white and green asparagus on the farm's 889 acres.

When asked about the importance of his foreigners, Buschmann likes to reply that three harvest workers secure one German job, meaning the high productivity of Polish laborers allows the farm to employ Germans in other parts of the industry.

"Were it not for the Poles, we'd have to close down," he says.