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Browsing by Author "Tessore, Carlos"

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    Effect of tillage system and nitrogen rate on tomato yield
    Tessore, Carlos (Virginia Polytechnic Institute and State University, 1982)
    Experiments to evaluate the effects of tillage systems and nitrogen fertilizer rates on fresh market 'Pik Red' tomato (Lycopersicon esculentum Mill.) production were carried out at Blacksburg, Virginia (1981 and 1982) and at Carrasco and Jackson, Uruguay (1981-2). Two tillage systems were used: (a) conventional tillage (CT) - plowed, disced and rototilled, and (b) no-tillage (NT) using paraquat at 0.5 kg/ha. Four different nitrogen (N) rates were used: 40, 80 and 120 kg N/ha broadcast at transplanting and a 40/40 kg N/ha split applications - 40 kg N at transplanting and another 40 kg N after the flowers of the first cluster had set. During 1982, at Blacksburg a 0 kg N/ha rate was added. For all locations and years, water availability was equal or higher in NT plots than with CT after transplanting. The largest differences were found at the beginning of the growing season. Soil under NT tended to be cooler than under CT; these differences in soil temperature are attributed to higher moisture content with NT than CT and the shading effect of the mulch in the NT plots. Soil Nitrate (NO3) content was equal or lower with NT than with CT at Carrasco and Jackson. Absorption of NO3 by the rye cover crop in NT plots probably was a major cause of NO3 differences between tillage systems. Nitrogen, P and K content in leaf tissue were equal or higher while Ca and Mg were equal or lower in NT plants than in CT plants. Nitrogen tissue content was increased by the N rate only at Carrasco; no effect of N rate was found on absorption of other nutrients at Carrasco or Jackson. Total yield was not affected by the tillage systems except for Blacksburg in 1982 when the NT plots outyielded CT plots. Marketable yield was consistently increased by the NT system at all locations and years. Unmarketable yield was equal or higher with CT than with NT. No effect of the N rate was found for any yield or yield components except for Blacksburg in 1981 where the total average weight was affected by the N rate. Water availability rather than N supply is believed to be the limiting factor to yield production at all locations and years. Blossom-end rot was consistently reduced by the NT system at all locations and years. Improved water availability with NT than with CT was probably responsible for a more steady Ca supply to growing fruit with NT than with CT, thus reducing the incidence of the disorder.