PIVETTA, C.R. et al. Effects of irrigation with injection of air in soil moisture, nitrate avail­ability, electrical conductivity and lettuce productivity grown in plastic greenhouse. []. , 33, 1, pp.70-78. ISSN 0871-018X.

The objective of the present study was to evaluate the effect of the air injection through subsurface drip irrigation (oxyga­tion) in soil moisture, availability of nitro­gen oxide, and electrical conductivity, plant growth and yield of lettuce, variety "Men­tion", cultivated in plastic greenhouse. The experiment was carried out at the Mitra-ICAM, an Experimental Station of the Uni­versity of Évora -Portugal. The experiment was arranged in a randomized block design with four replications and the treatments were: irrigation with (CAR) and without (SAR) air injection. The air was introduced into irrigation water through a jet "Mazzei". The soil moisture in the surface layer (0­0.05 m) was similar for the two treatments, reaching values around zero. Concerning NO3^-concentration in 0.10-0.20 m soil layer at 35 and 47 days after planting was higher in the treatment CAR. At 47 days after plant­ing, the average levels of NO3^-were 95.33 and 67.94 ppm respectively in treatments CAR and SAR. Air injection increased root length density at 0-0.10m depth. The com­mercial yield was not affected by air injec­tion. The lack of response by the crop to the increase of the soil nitrate concentration and root length density could be related with the short cycle of the crop and/or with high con­tents of nitrogen present in the soil, or result of the dripline setting depth.

: Lactuca sativa L.; oxygation, root length density; subsurface drip irrigation.

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