This study was conducted during two different seasons to determine the best concentration of gibberellic acid (GA3) that
could result in better growth and higher yield of groundnut (Arachis hypogaea L.). Experiments were conducted during
the 2015 dry season and 2016 wet season at the field of the Universiti Kebangsaan Malaysia (UKM), Bangi, Selangor,
Malaysia. The purpose of the experiments was to investigate the response of the groundnut plants to four levels of GA3
(0, 50, 100 and 150 mg L−1) as foliar spray at 21 and 42 days after sowing. The treatments were laid out in a randomized
complete block design and replicated thrice. The results showed that the treatment of 150 mg L−1 GA3 significantly
(p<0.05) increased plant height, number of branches per plant, total dry weight, number of pods per plant, pod yield,
100 seed weight, % shelling, oil content, protein content, seed moisture and germination percentage during the wet and
dry seasons. In conclusion, the 150 mg L−1 GA3 concentration is the optimum level required to enhance the growth and
yield in groundnuts during the wet and dry seasons.
Experiments were carried out in the laboratory and greenhouse to determine the growth inhibitory effects of Grassohopper’s cyperus (Cyperus iria L.) on the seedlings of 5 Malaysian rice varieties namely MR211, MRQ74, MR220, MR84 and MR232. Three concentrations of the aqueous extract of the weed (12.5, 25.0 and 50.0 g/l) and weed debris (5, 10 and 20 g dry debris/1000 g soil) were used to test the allelopathic effect of
C. iria on the growth of the rice plants. The weed leaf, stem and root extracts reduced the growth of the rice seedlings and showed selective activity in the varieties. The C. iria leaf and stem extracts showed comparatively higher growth inhibitory effects than those from the root. The weed extract caused more reduction in the root length of the rice plant compared to the shoot length. Among the rice varieties tested, MR232 was found to be more susceptible to the weed inhibitory effect. The leaf extract of C. iria at full strength caused root and shoot reduction of MR232 by 88.1% and 73.1% respectively (compared to the control). In most cases the fresh weight of the rice seedlings were more affected than the plant height. Weed debris caused significant reduction of leaf chlorophyll content in all the rice varieties tested with the exception of MR211. The chlorophyll content of MR232 was greatly affected by the weed debris which caused reduction of 36.4% compared to the control. The inhibitory effects of weed extracts and debris on rice growth
parameters were found to be concentration dependent.
The adsorption equilibrium time and effects of pH and concentration of ¹⁴C-labeled chlorpyrifos
O,O-diethyl O-(3, 5, 6 trichloro-2-pyridyl)-phosphorothiote in soil were investigated. Two types of Malaysian soil under oil palm were used in this study; namely clay loam and clay soil obtained from the Sungai Sedu and Kuala Lumpur International Airport (KLIA) Estates, respectively. Equilibrium studies of chlorpyrifos between the agricultural soil and the pesticide solution were conducted. Adsorption equilibrium time was achieved within 6 and 24 hours for clay loam and clay soil, respectively. It was found that chlorpyrifos adsorbed by the soil samples was characterized by an initial rapid adsorption after which adsorption remained approximately constant. The percentage of ¹⁴C-labeled chlorpyrifos adsorption on soil was found to be higher in clay loam than in clay soils. Results of the study demonstrated that pH affected the adsorption of chlorpyrifos on both clay loam and clay soils. The adsorption of chlorpyrifos on both types of soil was higher at low pH with the adsorption reduced as the pH increased. Results also suggest that chlorpyrifos sorption by soil is concentration dependent.
Heavy reliance on herbicides for goosegrass (Eleusine indica Gaertn.) control has led to the development of paraquat,
glufosinate, fluazifop and/or glyphosate resistance in goosegrass. This study aimed to evaluate the efficacy of preemergence
herbicide, S-metolachlor-treated oil palm frond powder on inhibition of resistant biotypes of goosegrass
under glasshouse and field conditions. The oil palm frond (OPF) powder was treated with S-metolachlor at its suboptimal
rate and applied as mulch. The herbicide-resistant goosegrass plants were found to be more inhibited when treated
with S-metolachlor-treated OPF mulch at the rate of 12 g ai ha–1 S-metolachlor + 1.5 t ha–1 OPF (with the exception of
the glufosinate-resistant googegrass biotype in the sandy loam soil) compared to the growth of the resistant biotypes
in silty loam soil under glasshouse conditions. Field experiments in an ambarella (Spondias dulcis L.) farm further
showed that OPF -treated with S-metolachlor mulch at the rate of 32.0 g ai ha–1 S-metolachlor + 4.0 t ha–1 OPF provided
great suppression of glyphosate-resistant biotypes of goosegrass with more than 85% reduction of weed density and
biomass, respectively. These results suggested that the residue of OPF have the potential to reduce the application rate
of S-metolachor without compromising on the excellent control obtained in combating these herbicide-resistant biotypes
of goosegrass.