Crop Responses

Abstract

The greenhouse gas CO₂ was considered as plant nutrient when its role in photosynthesis identified. Kimball (1983) analyzed the response of 430 crop species. Strain and Sionit (1982) edited 778 references to demonstrate CO₂-induced increase in growth and productivity of crop plants. The positive impact of elevated CO₂ was recognized as early as 1888 in England for food crops and flowers (Lundegardh, 1920–23). Brown and Escombe (1902) reported negative effects of CO₂ as downward curling of leaves and aborting of buds, which were attributed to the impurities in the CO₂. Sixteen species of plants, which were grown in CO₂-enriched (1500ul/l^-1) greenhouses, showed a 160% increase in plant weight varying from 97% for Fuchsia to 262% for Geranium. Cummings and Jones (1909–1914) did first field experiment using CO₂ produced by mixing Na₂CO₃ and H₂SO₄ and demonstrated increased yields of pods and seeds of peas and beans, larger potato tubers, heavier leaves and early fruits, and higher yield of strawberries; however, no detail is given as to how the concentration of CO₂ was measured and supplied for 8 hrs per day to these crops. The CO₂ produced by burning of charcoal, coal gas, per peats, and purified gas from smelter and furnaces was used for growing greenhouse vegetables in Northern Europe. Reinae (1931–1917) reported the beneficial use of CO₂ fertilization in 6000 nurseries for commercial vegetable and flower growing in Germany. The old Chestnut Experimental Station in England (1926–1930) found an increase of 30% in the yield of greenhouse tomatoes due to CO₂ enrichment. However, they did not recommend the CO₂ enrichment technology for the commercial use. Interest has been aroused in the commercialization of greenhouse crop production in the western world during 1961 when Dutch grower Gravenzande marketed winter lettuce of greater weight and better quality. Subsequently 4000 acres of lettuce were grown in CO₂-enriched environment in the Netherland in 1961. Gaastra (1959) made physiological studies on the process of photosynthesis in CO₂ grown tomato and cucumber. Goldsberry and Holey (1962) reported the use of CO₂ fertilization in the flowering industry by inducing higher yield, better flower texture, and shorter production cycle along with other benefits (Wittwer 1986; Uprety 2014). Many papers relating to the use of CO₂ enrichment technologies appeared in International Horticultural Congress in 1962. However, no such papers were published from the USA. USA has not used CO₂ enrichment in greenhouse environment till 1960. Keeling in his first observation reported an exponential rise in the atmospheric CO₂ from 315 ul/l^-1 in 1958 to 344 in 1976. Elevated CO₂-controlled greenhouses were beneficial for many vegetables and flower crops during the months of spring. However, there is little benefit of additional CO₂ in an adequately ventilated greenhouse. (*Quoted from Wittwer (1986)) (Table 5.1).