Seeds of eight common cropping and fallow weed associates of maize (Zea mays L.) were collected after crop harvest from mature plants in the rainforest zone of southwestern Nigeria and analysed for their P, K, Ca, Mg, Na and Fe contents. Seed mineral contents varied differently with year, weed species and weed taxa. The following weeds had the highest 2-yr. average seed content of specified minerals Ageratum conyzoides L. (P), Aspila africana (Pers.) C.D. Adams (Ca, Mg, Na) and Melanthera scandens (Schum & Thonn.) Roberty (K, Fe). Seed Fe content of both A. africana and Senna occidentalis L. was comparable to that of M. scandens. The lowest mineral contents were observed for S. occidentalis (P, K), Calcopogonium mucunoides Desv. (Ca, Mg, Na) and C. olitorius (Fe). Asteraceae had considerably higher seed P and Ca contents but fairly higher contents of K, Mg, Na and Fe than the other weed families. Seed mineral contents were poorly correlated across weed species and years of sampling, except for Na and Ca. In Asteraceae, Mg and Ca or Na, Na and Ca or Fe and Fe and K were highly correlated. Also, only T. procumbens and M. scandens were significantly correlated in seed mineral contents. It is concluded that weeds with very high seed mineral contents, especially P, K, Ca and Mg may be left in the field after crop harvest and allowed to shed their seeds. From the standpoint of soil fertility restoration, the decay of such seeds in the soil releases more locked-up nutrients in addition to that recovered from weed debris. However, there is a need to prevent weed resurgence during subsequent cropping by application of suitable pre-emergence herbicide.
PAPER TITLE :POST-HARVEST SEED MINERAL COMPOSITION OF SOME COMMON CEREAL WEEDS IN THE RAINFOREST ZONE OF SOUTHWES
JOURNAL Of SUSTAINABLE TECHNOLOGY | VOLUME 4 NUMBER 1 2013
- Author(s) : SMITH, M.A.K. and AMOO, I.A