Pea research findings at Winchmore

Press, Volume CXIV, Issue 33424, 4 January 1974, Page 11

Pea research findings at Winchmore

I he area of peas grown in Canterbury has doubled over the last live or six years. In the Ashburton county alone some 9000 hectares (22,500 acres) of field peas and 2000 hectares (5000 acres) of garden peas for seed were grown last season. An additional outlet for garden peas is through the food processing industry. Garden peas harvested at the fresh pea stage for the processors are known as viner peas. The two factories in Christchurch and one in Timaru account for about 3000 hectares (7500 acres) annually.

At the Winchmore irrigation research station, situated on a Lismore stony silt loam, various aspects of pea growing have been studied. These include variety trials and investigations on time of sowing, the effect of molybdenum, irrigation requirements and sowing rates. At the present time work with peas is concentrated on irrigation and sowing rate studies. The variety Greenfeast has been used and it has been harvested at the processing stage. How'ever, the results are probably applicable to other varieties and to seed harvesting. The sowing rate studies have been done on both dry

and irrigated crops. There is some evidence that yields are improved by sowing at rates above those normally

used. Last season five sowing rates were tested but the maximum population established (82 plants per square metre) was only in the order of normal farm practice. However, yield increased in step with the population up to the maximum population tested — even in the non-irrigated treatment. As it is generally recognised that the optimum population is higher in irrigated crops, it is probable that sowing rates should be increased where irrigation is applied. This work is being continued with higher sowing rates in order to confirm these results and provide more precise recommendations.

The object of the irrigation studies has been to ascertain the moisture requirements of the crop dur-

ing different phases of growth. It is known from overseas work that the flowering phase is very sensitive to moisture stress. Under dry conditions irrigation during this phase causes large increases in yield.

There is less certainty regarding the benefits of irrigation both before flowering and during pod swelling. In fact different people have found a positive, negative or nil yield response to irrigation before flowering. It seems probable that the response to irrigation depends both on the phase of growth of the crop and how dry the soil is at the time of irrigation.

At Winchmore trials have been run in which the crop has been flood irrigated at different soil moisture levels during the different phases of growth. The results of these trials ' indicate that irrigation should only be given before flowering if! moisture falls to 25 per cent available. However, from, the start of flowering irriga- : tion should be applied to 1 keep soil moisture above 50 j per cent available.

In practical terms, on a light soil an irrigation before flowering will only be necessary in a dry season. From the start of flowering either two or three irrigations will be required depending on whether it is a normal or dry season.

Over-irrigation before flowering can cause too much vegetative growth and a reduction in the yield of peas. On heavier soil types the irrigation requirement may be slightly less. An obvious point arising from these irrigation trials is the large response to irrigation particularly when it has been dry during flowering. For instance,; in the 1971-72 season yield from the non-irrigated treatment was 2400 kilograms per hectare (21001 b per acre), whereas average yields from the different irrigation treatments were in excess of 7000 kg/ha (61601 b per acre). The increased yield with irrigation has been found to be mainly due to a lower I abscission of flowers and young pods. At harvest aj non-irrigated crop may have an average of 2.51 pods per plant whereas an irrigated crop may average, 4.5. The number of peas' in each pod and individual pea weight may also be slightly greater with irrigation.

A word of warning should be given about the irrigation of peas—apply the water as uniformly as possible. Irrigation delays maturity and in most seasons this is by about seven to 10 days, if a strip is missed when watering a paddock that strip will not only yield less but will also \ be overmature at harvest. Serious cases of poor irrigation in viner peas can make the crop unacceptable for processing. 1

The accompanying item on pea research at Winchmore irrigation research station has been written by a scientist at the station. Dr R. Stoker.