But Mr. Castro has refused to allow what many farmers and experts see as an obvious solution to the shortages of transportation and equipment: Let people import supplies on their own. “It’s about control,” said Philip Peters, a Cuba analyst with the Lexington Institute, a Virginia-based research group.

Other analysts agree, noting that though the agricultural reforms have gone farther than other changes — like those that allow for self-employment — they remain constrained by politics.

“The government is not ready to let go,” said Ted Henken, a Latin American studies professor at Baruch College. “They are sending the message that they want to let go, or are trying to let go, but what they have is still a mechanism of control.”

For many farmers, that explains why land leases last for 10 years with a chance to renew, not indefinitely or the 99 years offered to foreign developers. It is also why many farmers say they will not build homes on the land they lease, despite a concession this year to allow doing so.

Mistrust is widespread. To get the growth Mr. Castro wants in agriculture and the economy, people need to trust the government, analysts say. But after half a century of strict control, many Cubans doubt proclamations from officials, who insist that this time, despite previous crackdowns, private enterprise will be supported.

Some farmers still wonder when the government is going to swoop in and take what they have built.

“What concerns me is that in a place like this, after five or six years the state might need the land to complete some kind of project,” said Reinaldo Berdecia, who is raising cows outside Havana.