The sister of slain Feilding farmer Scott Guy has told a court her husband, murder accused Ewen Macdonald, checked to see if both men were getting paid the same amount for their work on the farm.

Macdonald, 32, is accused of shooting dead his brother-in-law in his driveway in July 2010 because of tensions over the future of the family dairy farm.

The high-profile trial is into its second week in the High Court at Wellington, this week focusing on the relationship between the two men.

On Wednesday, Macdonald's wife Anna said he had checked the wage book in the farm office.

"He wasn't taking anything but he was looking, checking up," she said.

Ms Macdonald said her husband started working harder on the farm so he could provide for her and their children.

She also told the jury she had reservations about going into a business partnership with her parents and Scott and Kylee Guy.

"I wasn't so sure, because I don't think three's a great number. Two's company and three's a crowd," she said.

Earlier on Wednesday, Mr Guy's wife, Kylee, and his father, Bryan, gave evidence.

Bryan Guy told the court his son and Macdonald did different jobs on the farm - Macdonald doing long hours with milking and Mr Guy doing some long hours during cropping, Fairfax reports.

"I recognised that Scott particularly wouldn't do as many hours as Ewen so he could contribute to the milking."

However, the court has heard Mr Guy was not so interested in the dairy side of the operation, and concentrated on the cropping aspect.

The court was also told Mr Guy had thought he could inherit the family farm.

At a shareholder meeting Mr Guy brought up inheriting for the first time, which surprised him, Bryan Guy said.

"Perhaps because he was the oldest son," he said.

Bryan Guy said he then explained to his son that he had not inherited the business from his father, rather he had to buy him out.