Weed interference in upland rice: I. row spacing and nitrogen rate effects in the nutrients concentration in the rice and weed plants

Abstract

The essay insered in a global study about the spacing and nitrogen rate effects on the competitive relationship between weeds and upland rice crop. The treatments were located in a factorial desing 2x2x3 , when the variables were: two weed managment conditions - weeded and not weeded during all rice cycle - two row spacing - 0.40 and 0.60, e three nitrogen rate - 2.4 , 2.8 and 7.2 g de N/m of row. The essay was installed on Latossolo Vermelho Escuro sandy phase soil. Two valuations were realized: the first in the crop tillerinq and the second in the crop flowering. In the tillering phase the most important weed were Digitaria horizontalis and Indigofera hirsuta. The first weed showed higher contents of K, Mg, Fe and Mn and lower contents of N and Ca than the legumonosous weed. In comparison with the weeds, the rice contents of N, P, Fe, Mn and Zn were higher, the contents of Ca and Mg were lower. The K and Cu rice contents were lower than in D.horizontal in and higher than in l.hirsuta. In the flowering phase, the rice showed higher contents of P, Cu, Mn and Zn and lower contents of N, K, Ca, Mg and Fe, than the weed community. The row spacing and nitrogen rate effects showed different aspects, in according with the nutrient, weed especie and valuation period. In general, the weed effects were more drastics on the 0.60 m row spacing.