By Peter Murphy
BOGOTA, April 28 (Reuters) - Farmers across Colombia began protests on Monday demanding the government enact reforms it promised last year, organizers said, demonstrations that could unsettle President Juan Manuel Santos as he runs for re-election in four weeks.
Colombian producers of coffee, potatoes, rice, onions, tomatoes and other crops say the government has failed to alleviate indebtedness and regulate prices for inputs like fertilizer, among other measures they say were promised in August to end protests that turned violent.
The government argues it has been working on the reforms though some can only be implemented over the long term.
"It's a national day of protests by farmers across Colombia," said Victor Correa, spokesman for the Dignidad Cafetero coffee growers' protest movement. "We are complaining about the government not fulfilling the agreements of August last year."
He said peaceful protests were taking place in 15 of Colombia's 32 provinces though some of the groups were blocking roads. He conceded participation this time was likely to be smaller because a near 70 percent increase in coffee prices since August that has soothed the sector's anger.
Nonetheless, it comes at a critical moment for Santos who is seeking a second four-year term in elections on May 25 as the protests turn the spotlight on a sector that some Colombians believe has been neglected by the government.
Center-right Santos has said the protests are deliberately designed to damage his election campaign. If they escalate they could boost support for right-wing Oscar Ivan Zuluaga and the Green Alliance's Enrique Penalosa, his two main rivals.
Santos' popularity plunged to a record low of 21 percent immediately following last year's protests from above 50 percent. A poll this weekend by Ipsos Napoleon Franco showed Santos would likely win the election but need a second round.
Defense Minister Juan Carlos Pinzon has warned that the Andean nation's leftist rebels, fighting the government for five decades, are inciting the protests. Farming groups dispute that, arguing the demonstrations have clear and legitimate aims.
Correa of the coffee farmers' protest movement said producers were due to meet with Agriculture Minister Ruben Dario Lizarralde later on Monday. The ministry has released press statements in recent days highlighting the attention the government has been giving to the sector.
Last year's protests turned violent as the armed forces used tear gas to end road blockades that cut off food supplies to some towns. The protests culminated with demonstrations in a main square in the capital Bogota. Students joined the protests and smashed shop windows. (Editing by Cynthia Osterman)