2 February 1996

reduced inputs – SAME EFFICaCY

TIGHTENING controls on slurry and herbicide use in Holland have concentrated research efforts on reducing application rates while maintaining efficacy.

Wim van Dijk of the Lelystad research station, Holland, told Maize Growers Association members on a technical tour of Holland that manure applications often exceeded crop requirements.

"Any nitrogen uptake usually ceases after flowering so applications after this point will be wasted. While in early spring, yellowing of the plant is often caused by cold, but mistaken for a lack of nitrogen," said Mr van Dijk.

Four to eight weeks post emergence root growth is poor and nutrient uptakes limited.

"Reducing soil compaction will help roots develop and improve nutrient use. And placing nitrogen 5cm from the plant, both dry matter yields and nitrogen uptake can be increased."

Leaching losses of herbicide resulting from atrazine use and continuous cropping have prompted the Dutch government to restrict the level of active ingredients applied to 1kg/ha by the year 2000. But, current rates for maize plants are above 2kg/ha.

"Weed control should be based on preventing the dispersal of weed seeds by cleaning machinery and ensuring manure is stored for over three months to reduce the number of viable weed seeds."

Mechanical weed control trials at Lelystad showed that pre-emergence harrowing to 2cm (0.3in) depth above seed planted to 6cm (0.9in) depth and followed by inter-row cultivation and hoeing destroyed 90% of weeds. But dry matter yields were about 2% lower than maize sprayed with low dose rates of chemicals.

"Low dose rates of a combination of contact and residual chemicals including terbuthylazine instead of atrazine at planting and fourth to fifth leaf stage destroyed 99% of weeds. Using more acceptable chemicals on younger plants has enabled us to reduce the amount of active ingredient by up to 1kg/ha," said Dr van Dijk. &#42

Wim van Dijk: "Leaching losses of herbicide applied to maize have prompted the Dutch government to restrict active ingredients to 1kg/ha."