Nutrients absorption and balance on rotation system for lettuce [Lactuca sativa] cultivation

We examined the nutrient absorption and balance on three models of rotational cropping for lettuce cultivation by field experiment from 2001 to 2003. The model which includes leaf vegetables such as cabbage, Chinese cabbage and lettuce had the best potassium balance, since those crops contain a large amount of potassium in the leaves. Chinese cabbage absorbed the largest amount of NPK elements among the tested crops. The model which includes soybean, buckwheat, and corn showed the best nitrogen balance and good potassium balance. We believe that the rates of fertilizer application for soybean and buckwheat were considerably lower than those of leaf vegetables thus their nutrient balance was improved. The model which include Welsh onion had the worst NPK elements balance. The rate of fertilizer application for Welsh onion was larger than lettuce although the amount of nutrients absorption of Welsh onion was equal with lettuce. Both rye and oats which cropped as green manure in all the models absorbed nitrogen and potassium a lot; cropping of them was effective in improvement of the nutrients balance. Obviously, every model showed worse phosphorus balance; accumulation of available phosphorus in topsoil was observed in both methods of continuous cropping of lettuce and the three rotational cropping models. Concerning the several crops in rotational cropping system for lettuce, the experiment revealed the amount and the rate of NPK elements in leaf, stem, grain and root respectively.