2 February 1996

twin rows suit worcs system

Planting 30% more seed in double parallel rows can boost yields of high quality maize silage. Robert Davies reports

WORCS farm manager Steve Pritchard is convinced planting maize in double rows has a place.

Maize has been grown on the 283ha (700-acre) estate at Little Malvern Farms, Welland, for about 20 years. The crop does well on east facing sloping land running up to 180m (600ft) under the Malvern Hills. About 121ha (300 acres) are sown each year to provide 75 to 80% of the forage dry matter included in a complete feed for 320 dairy cows.

Mr Pritchard began using twin rows for part of the crop three seasons ago. He was looking for a way of using very early varieties to get high cob weights without sacrificing dry matter yield.

The varieties used are Avisto and Calypso. Both are semi-dwarf varieties that often fail to impress visually as a standing crop when compared with taller, very high yielding varieties. But they resist lodging and produce 60% of total dry matter as cobs.

Grown conventionally, says Mr Pritchard, they can produce disappointing yields. More widely spaced in twin rows, with a plant population of 130,000/ha (52,533/acre) compared with the normal 100,000/ha, 10% higher total dry matter yields can be obtained. This allows the benefits of the varieties high cob to stem ratio to be exploited fully.

Sowing about Apr 25 is done by contractor using a modified drill. Because there could be problems harvesting the headlands using an unmodified header these are drilled conventionally. But 24ha (60 acres) of the total maize crop is sown in twin rows.

The drill is fitted with six extra units and an additional fan. These are lifted out of action when the headlands are done. Before the modification was made oversowing was practised but it proved hard to see the marks of the previous pass and the method was also expensive in time and fuel.

Seeds are placed 16cm (6in) apart in the double rows, which have a 30cm (12in) gap. The twin rows themselves are 40cm (16in) apart, which allows them to be harvested with the estates own self-propelled, hydrostatic-drive harvester.

Mr Pritchard has no precise comparison of fresh yields from twin and single rowed maize. But he knows that in a conventional maize crop the harvester can operate at a forward speed of 4.5 to 5mph. Harvesting twin rows it has to move 1.5 to 2mph slower.

Experience has shown there is sufficient light and air between plants to avoid problems normally associated with high plant densities. Water can be a problem, which was evident in the 1995 drought. Mr Pritchard used the twin-row technique on land less susceptible to moisture deficiency.

"Last year the double rows did not show moisture stress as early as the rest of the maize but suffered more badly later," he says. "In two of the past three years dry matter yields have been about 15% higher than from early varieties grown conventionally. It is a system for farmers who are going for quality by sowing very early maturing varieties."

Ideally he would like to be able to pick-and-mix high and average quality maize silages when mixing the complete ration. But this has not been possible since switching to one large silo.

Fertilising the twin-rowed crop is the same as with single rows – a heavy dressing of slurry and 70kg/ha of diammonium phosphate placed close to the seeds. A deep soil nitrogen analysis is done in the spring and a dressing applied to make up for any nitrogen not supplied by the slurry.

A trial Mr Pritchard conducted in 1995 was intended to compare the performance of the two varieties normally used in twin rows with another that might be suitable and one likely to be totally unsuitable. The seed was sown at 100,000 and 130,000/ha in conventional rows and 130,000/ha in double rows. Unfortunately the drought ruined the comparison. &#42

Maize is planted in double rows at Little Malvern Farms to enable use of very early varieties to secure high cob weights without sacrificing dry matter yield.