The commercial growing of tobacco in New Zealand is at present limited to the Waimea county of Nelson Province. Most of the area is close to the town of Motueka. Soil and climate favour this locality. The best soils for producing heavy crops of good-quality leaf are sandy silt loams of the river valleys. The largest area of this soil type is in the Riwaka district. Tobacco is also grown on heavier soil types in other river valleys in the area. The Motueka district has an annual rainfall of about 40 in., reasonably evenly spread throughout the year. It is very sunny (about 2,500 hours a year) and free from wind. Hot days, with temperatures of up to 90° F, with warm and humid nights, suit tobacco.
The yield per acre has steadily increased with better varieties and better cultural practices: from 600 lb of dried leaf per acre in 1935–37 to 1,200 lb in 1945–47 and 1,600 lb in 1963–64. The total crop for 1963–64 season was over 9 million pounds from 5,800 planted acres. In 1963–64 the amount of domestic leaf used in manufacture was 50 per cent of the total.
The main variety grown is Virginia Gold – a fluecured type which crops heavily and is good for manufacture. About 95 per cent of the total grown is of this variety, the remainder being mostly Burley – air dried. The crop is grown under contract to the manufacturers. Seed is sown in beds on the farm. The soil in these beds is sterilised against soil pests and diseases. Seed is sown very thinly so that the young plants do not have to be handled before transplanting to the field. This practice reduces the spread of mosaic. Seed is normally sown in late August. Calico covers are fitted to the beds to shade the plants on extremely bright days and also to protect them from frost. Planting out in the field is normally done in November when fear of frost has passed, most of the area being planted by machines. Cultivation is continued while the crop is small enough to allow the passage of tractors. Almost all the area is irrigated. Harvesting begins in late January and continues until the first frosts in late April. Harvesting machines, both imported and locally made, are used on most of the larger farms. When harvesting stops the ground is thoroughly cultivated, often with a rotary cultivator, so that all stalks and trash are buried. Cover crops of short-rotation ryegrass or rye corn are grown in the winter.
The kilns in general use today are of the down-draught type capable of loading four to five sticks high. Drying takes five days. On unloading, the tobacco sticks are bulk stacked, generally in the grading shed. When the harvesting season is over the leaf is returned to the kiln for conditioning before grading. Conditioning consists of allowing the dry and brittle leaf to take up some moisture from the hot and humid kiln. This allows it to be handled without breaking. Grading is done on the farm and then the leaf is delivered to the factory.
Research into soil types and recommended fertiliser programmes, and chemical analyses of tobacco and soil, have been made by the Cawthron Institute in Nelson. The growers, the manufacturers, and the Department of Scientific and Industrial Research have a joint Tobacco Research Station. This station has bred varieties for local conditions and types resistant to black root rot. It also produces seed for the growers. There is a local breeding programme and, as well, new varieties from overseas are checked for suitability for local use. Fertiliser trials, disease-control trials, and drying experiments are all carried on. Experiments to prove the practicability of drying leaf in bulk are in progress. Small-scale trials in the 1960–61 season would appear to indicate that this should be possible.
The most prevalent diseases and pests are: Mosaic. (Nicotiana Virus I); Verticillium wilt (V. dahliae and V. albo-atrum); Black root rot (Thielaviopsis basicola); Leaf miner (Gnorimoschema operculella); and Cutworm (Heliothis armigera). A physiological effect causing bronzing of the leaf late in the season and, thought to be a form of chilling, can cause quite severe losses.
by Moore Grant Baumgart, B.SC., Horticultural Division, Department of Agriculture, Nelson.