Field-grown tomato response to carbonated water application

Direct release of CO2 gas to achieve a cost-effective method of atmospheric CO2 enrichment has not been proven feasible under field conditions. We hypothesized that greater efficiency of application would occur by applying CO2 via carbonated water and that application would also result in beneficial modifications of the soil environment. Our objectives were to evaluate crop, soil, and atmospheric CO2 responses to application of carbonated water under pressure through a drip irrigation system. Studies were conducted under mulched and unmulched conditions in 1988 using tomato (Lycopersicon esculentum Mill.). In 1989, carbonated water was applied at approximately 2-, 4-, and 6-d intervals to determine the effect of irrigation frequency. In 1988, a positive yield response of 9% was obtained in the presence of mulch. No response was observed in open beds. Fruit yields were increased at all three irrigation frequencies in 1989, with increases in fresh-market and total fruit yields averaging 16.4 and 15.9%, respectively. Atmospheric enrichment was observed during carbonated water application, but residual enrichment between irrigations was difficult to detect. Significant increase in soil-air CO2 from carbonated water application was noted throughout the intervals between successive irrigation events. Carbonated water application also decreased soil pH for periods of up to 5 d after irrigation and increased apparent uptake of P, K, Ca, Mg, Zn, Fe, Mn, Cu, and B. Based on the limited duration of enrichment relative to the entire growing season for any of the carbonated water treatments, the yield responses observed could not be attributed solely to atmospheric enrichment. Thus, we conclude that yield increases resulted from the combined effects of limited atmospheric CO2 enrichment and soil environment modifications leading to improved nutrient uptake.