THE SOIL FERTILITY EFFECTS OF LEGUMINOUS LEY PASTURES IN NORTHEAST THAILAND .1. EFFECTS ON THE GROWTH OF RESELLE (HIBISCUS-SABDARRIFA CV ALTISSIMA) AND CASSAVA (MANIHOT-ESCULENTA)
Ta. Gibson et Sa. Waring, THE SOIL FERTILITY EFFECTS OF LEGUMINOUS LEY PASTURES IN NORTHEAST THAILAND .1. EFFECTS ON THE GROWTH OF RESELLE (HIBISCUS-SABDARRIFA CV ALTISSIMA) AND CASSAVA (MANIHOT-ESCULENTA), Field crops research, 39(2-3), 1994, pp. 119-127
The effect of ley treatments (mostly grazed) differing in legume speci
es, duration of ley and non-nitrogenous fertilization on the growth of
cassava and roselle is reported. Experiments were conducted in upland
fields of farmers at Khon Kaen, Thialand. Soils at the experimental s
ite range from paleustults to quartzipsamments with a loamy-sand surfa
ce and are extremely infertile. Treatments included cassava and weed-f
allow controls, and monospecific legume swards of Siratro (Macroptiliu
m atropurpureum cv. Siratro), Verano (Stylosanthes hamata cv. Verano),
mimosa (Mimosa invisa var. inermis) and crotalaria (Crotalaria juncea
) grown for 1, 2 or 3 years, or intercropped with cassava, or grown al
one in alternate years with cassava followed by test crops of roselle
and cassava. Treatments were with and without non-nitrogenous fertiliz
er. Yields for the first test crop (roselle) in almost all fertilized
legume plots were significantly higher than for the fertilized cassava
control whereas in unfertilized plots there was no significant effect
. Yields were highest in comparable fertilized plots following Verano
or Siratro with crotalaria intermediate and mimosa the lowest. Yields
were highest for fertilized two- and three-year Verano and Siratro plo
ts and lower for fertilized one-year, alternating years or intercroppe
d plots. Yields for the second test crop (cassava) again showed a subs
tantial increase in most of the fertilized legume plots compared with
the cassava control with results generally similar to those for the fi
rst test crop. The test crop data show Verano and Siratro as the best
ley species and suggest an optimum ley period in the range of one to t
wo years with a cropping phase of approximately equivalent duration to
the ley phase. The nitrogen fertilizer value of a Siratro ley in the
first year of establishment was estimated to be 132 kg N ha-1. Land pr
eparation treatments, following a Siratro ley, of mulching, incorporat
ion and herbicide killing of the legume had no effect on subsequent yi
eld of roselle whereas grazed plots resulted in a lower yield.