Squash is another name for pumpkin. The plant is a member of the diverse ëcucurbití family - the Cucurbitaceae. The cucurbits are hugely important plants not only as sources of food for people and for farm animals but their dried shells also serve a myriad of functions such as for food and water containers and as sound boxes for musical instruments. For a very long time, the cucurbits have been traditional crop plants in each of the continents except (obviously) Antarctica. Records show them to have been important to human civilisation for well over 7000 years.
Cucurbit fruit come in a very wide range of shapes, sizes, colours, textures and flavours. Along with the tough-skinned squashes and gourds, this family also includes many familiar soft-skinned fruits such as zucchini (courgettes), marrows, melons, water melons, gherkins and cucumbers. Botanically speaking, we eat the fruit (flesh and seeds) rather than the vegetative parts of the plant but in the kitchen most cucurbits are thought of as vegetables rather than as fruit.
Gourds were probably the earliest food-plants introduced to New Zealand by Māori. Its seeds were much easier to carry on long sea journeys than the tubers of taro and kumara. In more recent times, the most familiar of the squashes grown here was the Whangaparāoa Crown Pumpkin. These fruit are large (30 cm, 4 kg), grey-skinned and with bright orange flesh. They kept well and so were available year round to be eaten as a vegetable or made into soup.
For the last 30 years, the vast majority of our squash crops (now about 95%) have been of a single genotype ñ the buttercup squash, Cucurbita maxima cv ëDelicaí. These are dark-green skinned and somewhat smaller (20 cm, 1.5 kg) than their predecessors. These modern squash are an excellent source of vitamin A and other essential nutrients and of dietary fibre. They are also lower in calories than vegetables of similar texture such as kumaras, parsnips and potatoes.
Buttercup squash is an important crop in New Zealand. It is now our fourth largest horticultural export earner (coming next after kiwifruit, pipfruit and onions) with a crop valued of about $70m. About 40% of the national crop comes from Hawkes Bay, another 40% from Gisborne with the balance of about 20% coming variously from the Auckland, Waikato, Manawatu and Canterbury regions. About 85% of our total squash production is exported, principally to Japan but also to a number of other emerging markets.
To ripen well, squash likes hot summer days and cool nights. It is principally this requirement that centres New Zealandís production in the Hawkes Bay and Gisborne regions. Of course the vagaries of the weather from season to season in our maritime climate conspire to bring about the ëgoodí and ëbadí years so familiar to growers.
Soil type is less critical for squash with the crop doing well in soils ranging from heavy to light. The soil should, however, be fertile and with a pH in the slightly-acid range, from 6 to 6.4. A soil pH below 5.5 (acid) or above 7.2 (neutral to alkaline) will usually cause nutritional problems. Soils are notoriously variable over quite short distances and these variations have significant influences on fruit quality in squash affecting its flavour, storage potential and also its susceptibility to pests and diseases.
While some plant species are more tolerant of poor soil conditions than others, all species respond favourably to soil management interventions that improve soil quality (aeration, drainage, organic matter, pH, mineral balance). Similarly with squash, a well-managed soil increases both yields and fruit quality and also helps to reduce the incidence and severity of pests and diseases.
The use of gypsum to help remedy poor soil aeration and drainage in heavy or compacted soils is recommended. To gain best advantage, gypsum should be distributed at a rate that depends on the severity of the problem ñ high rates (up to 4,000 kg/ha) in areas where soil problems are worst and lower rates where they are less severe. Some of the general comments on the use of gypsum for soil remediation in
arable cropping apply to squash.
The fruits of almost all plants contain much less calcium than their other organs such as leaves and shoots. This peculiarity arises because of aspects of a fruitís developmental physiology. As a result, the fruit of most commercial species (apples, kiwifruit, tomatoes etc) tend to suffer specific breakdown disorders associated with their low calcium status. Recent research with squash has linked poor storage quality and susceptibility to post-harvest rots to low calcium.
While most of our soils contain reasonably high levels of calcium, one should distinguish between a soilís high calcium content and the need to apply a soluble calcium fertiliser. The addition of soluble calcium at critical times of plant growth has been shown to improve production and quality in many fruit and vegetable crops ñ even on calcareous soils. This fits with the idea that the provision of ëluxuryí levels of soluble soil calcium may well result in small increases in fruit calcium and thus in economic reductions in the incidence of the low-calcium disorders. Gypsum is a good source of both calcium and sulphur and has the advantage of providing calcium without effecting soil pH. Another advantage is that this calcium is provided in a water-soluble form.
The lighter arable soils and also those low in organic matter are more easily leached and so can easily become nutrient deficient. Used as a fertiliser, gypsum at 1,200 kg/ha is a good source of both calcium and sulphur.
