ISHS Acta Horticulturae 548: International Symposium on Growing Media and Hydroponics
THE EFFECT OF GROWING MEDIA ON YIELD AND NITRATE CONCENTRATION IN LETTUCE (Lactuca sativa var. capitata L.) |
| Authors: | A.J. Stepowska, W. Kowalczyk |
| Keywords: | lettuce, nitrate, growing media, fertilization |
| DOI: | 10.17660/ActaHortic.2001.548.60 |
| Abstract:
The nitrates content in the plant is related to their biological activity. Under low light intensity conditions the speed of biochemical processes is slow and the nitrate level is high. In the autumn-winter season, under covers without artificial light the nitrate content in lettuce is over 4000 mg NO3- per kg of fresh weight (the Polish norm is 2000 mg NaNO3 ·kg-1 FW) even with a low level of mineral soil fertilisation. The lower nitrate level and good quality of lettuce head is possible to got thanks to controlled fertigation in the substrates. A peat substrate with a precultivated NPK level 145:155:290 mg·dm-3 was used to fill pots at capacity of 1,5 dm3 per plant (water feeding, without the fertilization). By decreasing the peat substrate capacity to 0.5 dm3 per plant, the pots were standing on PP watering mat. The heads were not significantly different than in other methods. The nitrate level was significant low (551-655 mg NO3·kg-1 FW in the pots on the mat). The effects of cultivation on the rockwool fertigated by the liquid of EC=1,7 mS·cm-1 were as follow: the average head weight 136 g (autumn)- 236 g (spring) and nitrate level 1350 mg NO3·kg-1 FW-3440 mg NO3·kg-1 FW. Application of the solution EC=1,0–2,1 mS·cm-1 and elimination of the nitrogen in the preharvest period, decreased the accumulation of nitrate without the waste of the yield and quality of the lettuce head. | |
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