The deputy agriculture minister, Sylvester Nguni, in a rare admission of failures in the nation's land redistribution programme, said in a state-run newspaper that many new farmers who received formerly white-owned land lacked the expertise to produce crops on what he called a "commercial and even subsistence level".
Even farmers with adequate resources still failed to produce "meaningful" crops, Nguni said in the Herald newspaper on Monday.
Despite good seasonal rains, Nguni predicted the harvest beginning around April would produce half of what had been expected.
"The truth is, most crops have adversely taken the brunt of the shortage of fertilisers, and this has inevitably slashed the yields by about 50%," he said.
In some areas where fertilisers were used, above-average rainfall had leached out crop nutrients and herbicides.
He said many new farmers lacked training and experience. The government's Agricultural Research and Extension department (AREX), which provides trainers and advisers, was understaffed and lacked transport and gasoline as the country suffers its worst economic period since independence in 1980.
Robert Mugabe, the president, has insisted his land redistribution programme, begun in 2000, was intended to correct imbalances in ownership dating from the colonial era.
Critics say, however, that prime farms were allocated to ruling party members, judges, city business owners, government supporters and law-enforcement officials with no farming experience.
The central bank governor, Gideon Gono, criticised some new farmers in October for using their land only as "weekend picnic venues".
Petrol shortages are increasing
Zimbabwe's economic woes
He also castigated some for allegedly using agricultural loans to buy luxury off-road vehicles for private use and profiteering by selling the subsidised gasoline available to resettled farmers at black-market prices that were inflated tenfold.
Nguni was receiving a donation of 28 bicycles for AREX experts, according to the Herald.
It said the department employed about 3000 extension officers, about half the 6000 it needed countrywide.
Last year Zimbabwe produced about 800,000 tonnes of corn.
The country consumes around 1.8 million tonnes a year. Before the chaotic and often violent seizures of thousands of white-owned commercial farms began in 2000, food surpluses were exported.
Last week, the state-run Tobacco Industry Marketing Board predicted a 50% drop in production estimates for the main, hard currency-earning crops this year, citing late and inadequate loans to growers and shortages of fertiliser, chemicals and gasoline.
Official inflation in the crumbling economy soared last month to 613%, one of the highest rates in the world, as the United Nations food agency distributed emergency food aid to more than three million people facing acute hard currency and food shortages.
At least five million of the 12.5 million population were likely to need food assistance before the next harvests, and food handouts were now expected to continue long afterward, according to UN experts and charity groups.