Effect of nitrogen, phosphorus and potassium availability on emergence, nodulation and growth of acidicole Trifolium arvense L. in alkaline soil

The acidicole behavior of many species is given by their inability to acquire enough P in alkaline soil, but reasons for acidicole (syn. calcifuge) behavior of Trifolium arvense have never been studied experimentally. We asked how emergence of seedlings, the survival of plants, the growth of aboveground organs, the nodulation and the growth of roots of this species is affected by different N, P and K supply in alkaline soil. In the years 2010 and 2011, we performed a pot experiment (ten N, P and K fertilizer treatments) with seeding of T. arvense into alkaline soil. The acidicole behavior of T. arvense proved to be connected with the inability of seedlings to acquire enough P during their emergence. In all treatments, T. arvense was not able to flower in the seeding year and in the second year it flowered only in P treatments. This indicates the biennial character of the species in the case of late seeding and points to a strong P limitation of flowering and seeds production in plants grown on alkaline soil. Without P addition, T. arvense was not able to develop beyond the seedling stage. Nodulation was positively affected by P application and negatively by N application. Although T. arvense is a typical species for P poor soils, it does not suffer from P toxicity under high P supply. We concluded that the acidicole behavior of T. arvense is based on its P limitation when growing on alkaline soil.