Residual Effects of Phosphorus and Micronutrients in Vegetable Growing Areas under Different Organomineral Fertilizer Doses

Abstract

Organomineral fertilizers (OFs) can provide the macro- and micronutrients contained in organic matter slowly and gradually throughout the crop cycle. However, the residual effect of this slow release is still unclear and needs to be better evaluated. In this context, the objective of this study was to evaluate the use of different doses of OF in the cultivation of vegetables and to quantify the residual effects of P, B, and Zn in the soil. A randomized block design was applied, using different doses of fertilizer as a P source, with four replications. In the randomized block design, different doses of OF were evaluated as a source of P (all with four repetitions): T1 = no P supplied (zero dose); T2 = 200 mg dm−3 of P2O5; T3 = 400 mg dm−3 of P2O5; T4 = 800 mg dm−3 of P2O5; and T5 = 1200 mg dm−3 of P2O5 plus an additional treatment with mineral fertilizer (MF) (200 mg dm−3 of P2O5). The fresh weight (FW) and dry weight (DW) and the nutritional status of the lettuce and cabbage were determined through leaf analysis at harvest. Soil analysis was also conducted before planting and immediately after harvest in order to assess soil P, B, and Zn content. The FW and DW cabbage production was higher when fertilization was used for the crop (either OF or MF). No differences were observed in the effects of the OF and MF doses in cabbage production, which ranged from 281.2 g plant−1 to 341.8 g plant−1, while lettuce production was highest in MF (45.1 g plant−1), followed by OF doses of 800 mg dm−3 (37.1 g plant−1) and 1200 mg dm−3 (36.8 g plant−1) of P2O5. OF fertilization had a beneficial residual effect on lettuce production, the FW and DW production of which increased as the OF doses increased (from 18.8 g plant−1 to 36.8 g plant−1 for FW and from 2.4 g plant−1 to 4.0 g plant−1 for DW). The highest doses of OF increased the availability of P and Zn in the soil and facilitated the absorption of nutrients by the cabbage and lettuce crops. In the cultivation of cabbage and lettuce, the residual effects of the P, B and Zn in the soil were higher under the highest doses of OF. An antagonistic effect between the P and Zn in the soil was evidenced in this study, and this needs to be confirmed in other subsequent studies.