* Italy not on track to hit EU decarbonisation goal on time

* More large solar farms needed to boost capacity, experts say

* Red tape, calls to protect landscape slow installations

* Government rules out specific incentives to big plants

MILAN/ROME, March 6 (Reuters) - Italy's energy transition is building on a myriad of solar panels mounted on roofs, but the country has installed far fewer large plants than its neighbours, data seen by Reuters show, signalling hurdles on Rome's path to decarbonisation.

Italy has added big solar farms worth 6 gigawatts (GW) since 2016, significantly less than Germany and Spain, where more than 20 GW of new capacity has been installed by building plants with a size of at least 1 MW, data from sector association SolarPower Europe show.

Brussels has set a carbon emission reduction target for Rome of 43.7% by 2030, but the right-wing government of Giorgia Meloni has already admitted that Italy is not on track to reach that goal.

To do so, experts estimate the country needs around 12 GW of new green capacity every year by 2030. With solar the country's largest source of renewable energy, that is hard to achieve without boosting the number of big photovoltaic plants.

"There is no way we can install 12 GW per year only through small plants," said Agostino Re Rebaudengo, head of Italy's sector lobby Elettricita Futura, adding a large solar park produces three times the energy of a rooftop plant with the same investment.

Italy has deployed around 22 GW in small plants, including a multitude of rooftop panels, since 2016 - more than France, Spain and the Netherlands - thanks in part to incentives for home improvements that are now being phased out.

Energy Minister Gilberto Pichetto Fratin says it is hard for Italy to build a lot of large plants because of the nature of Italian territory, which is more heavily built-up, with fewer open spaces, than neighbours like Spain.

The government is also sensitive to calls to protect nature and cultural assets, he said. "There is heritage to be preserved, which is huge," he told Reuters.

Strict rules to protect that and resistance by local administrations have made the life of large plant developers difficult.

The industry complains that large green projects are held back by a slow permitting process, while rooftop plants benefit from simplified procedures.

"The European Union has asked for authorisation procedures to be streamlined. This has not happened yet and needs to be resolved," Aldo Beolchini, Chief Investment Officer of solar investment group NextEnergy Capital, told Reuters.

An industry source, who asked not to be named, said the authorisation process for a large solar park can last more than four years in Italy, while in Spain they aim to realise the plant within two years of its inception.

"We need to make a leap and accelerate the development of large plants if we want to hit 2030 targets," said Nicola Monti, CEO of energy company Edison.

FUNDS EARMARKED

Italy plans to spend a significant part of the 194.4 billion euros ($210.83 billion) in post-COVID funds it will receive from the EU through 2026 on grids and infrastructure to help the green transition.

Some 55.5 billion euros will be devoted to projects including the upgrade of the power network.

Italy has earmarked around 2.2 billion euros to finance solar plants to serve the needs of small communities - mainly small installations, below the size of utility-scale plants - and 1.1 billion to build agrivoltaic parks.

"We have to develop both small and utility-scale plants, respecting the landscape," said Michele Governatori from climate think-tank ECCO.

To address local concerns over the impact on the landscape, developers have in some cases turned to old industrial areas for large projects.

Enel has picked the site of a mothballed power plant in the town of Trino Vercellese, Piedmont, to build an 87 MW solar park due to become one of the biggest solar plants in northern Italy.

Pichetto Fratin said he was confident Italy could speed up installations this year and gradually reach the government's goal to add 10 GW in green capacity each year to 2030 - a target which falls short of the experts' recommendation to add 12 GW.

In a sign that boosting development of big farms is possible, Spanish utility Iberdrola last week said it would soon start to build a 245 MW solar park in Sicily, the largest project in the country.

But Pichetto Fratin ruled out offering any specific incentives to large plant developers, because he said these could violate European rules on state aid.

"There is no specific measure that distinguishes between the large and the small," he said. "It won't be legally viable." ($1 = 0.9221 euros)

(Reporting by Francesca Landini and Angelo Amante; Writing by Angelo Amante; Editing by Jan Harvey)