ABSTRACT
This work aimed to verify the concentration and accumulation of N, P, K, Ca and Mg, due to the application of increasing doses of fertilizers and to determine the critical level of these nutrients in the soil and in the plant, in seedlings of 'sansão-do-campo' (Mimosa caesalpiniaefolia Benth.) produced in three types of soil (mesotrophicUltisol, alic Oxisol and distrofic Oxisol). The seedlings were planted in pots with a capacity of 2.1 dm3. The experiment was conducted from December 2004 to April 2005, in Viçosa, in Minas Gerais state. The treatments were defined according to a Baconian matrix, where the macronutrients varied in three different doses and two additional treatments (zero and base), with four replications. The seedlings of 'sansão- do-campo' had generally a higher content of N, P, K, Ca and Mg as their availability in the soil increased. This fact was reflected in a higher content of nutrients in all parts of the plant. However, in some cases, there was no evidence of any correspondent increase for this increase. In terms of critical level, the values that provided better growth of the plant were: N (16 to 17.3 g kg-1 in the shoot), P (77 to 110 mg dm -³ in the soil and 1 to 1.5 g kg-1 in the shoot), K (51 to 86.5 mg dm-3 in the soil and from 5.7 to 7.1 g kg-1 in th e shoot), c Ca (0.8 to 2.2 cmol c dm-³ in the soil and from 10 to 14.4 g kg-1 in the shoot) and Mg (0.2 to 0.25 cmol dm-³ soil from 1.3 to 2.4 g kg-1 in the shoot). However, for K and Ca, studies with doses are suggested within this range of values found for better definition of the critical level. Among the soils that were studied, the Oxisol showed to be more demanding of adding nutrients, especially N and P, for an adequate production of Mimosa caesalpiniaefolia seedlings.
Keywords:
critical level; production of seedlings; macronutrients; sansão-do-campo