Rice Growth and Nitrogen Uptake as Influenced by Water Management

SARIAM. O, Y.M. KHANIF & T. ZAHRAH

Rice (Oryza sativa L.) is grown in Malaysia mainly under flood irrigation. As water becomes increasingly scarce, demand for available water from urban and industrial sectors is likely to receive priority over irrigation. It is, therefore, necessary to adopt rice production practices that reduce water input without any adverse effects on rice growth and yield. A greenhouse study was conducted to evaluate the effects of water management practices on the growth and nitrogen (N) uptake of rice. The three water management practices studied on rice variety MR 84 and Siam were flooded, non fooded (NF)-saturated and NF field capacity. Nitrogen in the form of 15N-labelled urea (2.52% atom excess) was applied at a rate of 100 kg ha-1 in three splits. Tiller production, plant height, root growth and grain yield were adversely affected when rice was grown under NF-field capacity soil condition. Grain yield was 57.6 and 54.4% lower under NF-field capacity than flooded and NF-saturated soil condition , respectively. The lower grain yield from NF-field capacity soil resulted from few panicles, less spikelets per panicle and lower 1000-grain weight. However, maintaining soil at a NF-saturated level did not seriously affect rice growth. Rice growth, grain yield and N uptake from NF- saturated soil were comparable to rice grown under flooded condition. A lower nitrogen uptake and fertilizer N recovery under NF-field capacity were attributed to smaller root system, lower above-ground dry matter yield and greater N losses from alternate wetting and drying soil condition. These results showed that irrigated rice could be grown under reduced water input at saturated soil condition throughout the growth period without affecting growth, N uptake and yield.

Investigation of Sources, Method and Rates of Nitrogen Application in Mature Oil Palms

B.K.W.KWAN

Results of an experiment to determine the effect of different rates, methods of application of three N sources on the yield of oil palm on Paliu family soil were examined using repeated measure analysis. The three N sources viz. ammonium sulphate, granular urea (2.9 mm) and forestry-grade urea (7mm) were applied at rates of 0.4, 0.8 and 1.2 kg of N per palm per year. The results show that urea gave comparable response in yield to ammonium sulphate as well as a significant linear response to N rates. FFB yield was significantly affected by the method of application. Burial of fertilizers at two times a year gave inferior results and required two or three times more fertilizer to achieve comparable yield to overall application at two times a year or broadcast in the palm circle at times a year.

Modeling the Partitioning of Evapotranspiration in A Maize-Sunflower Intercrop

C.B.S. TEH, L.P. SIMMONDS & T.R. WHEELER

The primary purpose of this study was to model the partitioning of evapotranspiration in a maize- sunflower intercrop at various canopy covers. The Shuttleworth-Wallace (SW) model was extended for intercropping systems to include both crop transpiration and soil evaporation and allowing interaction between the two. To test the accuracy of the extended SW model, two field experiments of maize-sunflower intercrop were conducted in 1998 and 1999. Plant transpiration and soil evaporation were measured using sap flow gauges and lysimeters, respectively. The mean prediction error (simulated minus measured values) for transpiration was zero (which indicated no overall bias in estimation error), and its accuracy was not affected by plant growth stages, but simulated transpiration during high measured transpiration rates tended to be slightly underestimated. Overall , predictions for daily soil evaporation were also accurate. Model estimation errors were probably due to the simplified modeling of soil water content, stomatal resistance and soil heat flux as well as due to the uncertainties in characterizing the micrometeorological conditions. The SW’s prediction of transpiration was most sensitive to parameters most directly related to canopy characteristic such as the portioning of captured solar radiation, canopy resistance and bulk boundary layer resistance.

Survival of an Escherichia coli in a Sarawak Soil

T.Y. LING, A. KASING & A.L. MIJEN

Soil is a natural digestion system for animal wastes. However, land disposal sites and agricultural land pose serious threats to the quality of surface and groundwater. In this study, a clay loam, Semongok series, from Sarawak was inoculated with wild strain E. coli isolated from animal wastes. Results indicated that first order decay rate increased as temperature increased from 25?C to 35?C and as moisture decreased from saturation to air-dry. Lag period of the bacteria was found to be the longest (8 days) in saturated soil at 25?C and the shortest (1 day) in air-dried soil at 35?C. Interaction between temperature and moisture was significant. First order decay model can be used after lag period to estimate E. coli decay. The best data fit was obtained under cool wet condition. Temperature correction coefficient in the range of 25-35?C was 1.18. It is recommended that disposal animal wastes be carried out during hot dry seasons of the year.

Agronomic Practices to Alleviate Soil and Surface Runoff Losses in an Oil Palm Estate

B.B.F. SOON & H.W. HOONG

A study was carried out to determine the efficiency of different methods of fertilizer application for oil palm cultivation on slopping land in Sabah. The result showed that mean annual runoff loss recorded was 19.79% of the rainfall. Highest runoff was associated with the very wet months between September and December. Among the treatments, highest runoff was recorded in plots with pruned fronds stacked down the slope following the planting row (30.83%), followed by plots with contour stacked fronds (17.88%) and plots with contour stacked fronds+ silt pit (10.68%). Annual soil losses recorded were 21.73 t/ha, 4.91 t/ha for plots with pruned fronds stacked down the slope following planting row, contour stacked fronds and contour stacked fronds+ silt-pit respectively. Overall broadcast of fertilizer application was more superior to burial method statistically but not to split-pit on terraced areas. Results indicated soil losses caused by runoff and leaching were minimal if proper agronomic practices such as contour frond stacking had been implemented accordingly.

Modelling the Distribution of Water- Stable Aggregates

P.PONNIAH & C.B.S. TEH

The wet-sieving method using nested sieves is a common way to measure aggregates stability, but this method can only be used to measured the stability of whole soils, not the stability of individual aggregates size fractions. Thus, the main objective of this study was to develop a mechanistic model to estimate the amount of breakdown and distribution of aggregates in the usual wet-sieving method (using nested sieves). The amount of aggregate breakdown and its distribution in the various sieves are described in a series of equations. By using several key assumptions, these equations could be solved. The model was tested on several soil types of various textures and land use. For each soil, each of the six aggregate size fractions (5-8, 3-5, 2-3, 1-2, 0.5-1 and 0.3-0.5 mm) was wet-sieved separately to determine the actual breakdown and distribution of aggregates in the various sieves. The model showed good accuracy for several different soils despite not requiring any information about the properties of the soil or wet-sieving method. The mean estimation error of the model was 1.33 g (6.65%), and it also showed no bias in its estimation.

N2 Fixation, Plant Growth Enhancement and Root-Surface Colonization By Rhizobacteria in Association with Oil Palm Plantlets Under in Vitro Conditions

H. G. AMIR, Z. H. SHAMSUDDIN, M. S. HALIMI, M.F. RAMLAN & M. MARZIAH

Association of the N2 fixing plant growth promoting rhizobacteria (PGPR) with various non-leguminous crops has reinforced the importance of biological nitrogen fixation (BNF) and plant growth stimulation effects. This concept was demonstrated through a laboratory experiment using tissue cultured oil palm plantlets. Under in vitro conditions, sterilized tissue cultured oil palm plantlets were grown in test tubes. Tests were conducted to observe the ability of selected rhizobacteria to fix N2, promote plant growth, enhance essential nutrient uptake and colonize roots of the associated host plants. Results from the experiment show that Azospirillum spp. (Sp 7) could contribute up to 66% of the host plant N requirement (%Ndfa), while locally isolated Bacillus spp. (UPMB 13) recorded up to 55% Ndfa at D56. The inoculation (especially Sp 7 and UPMB 13) also caused a significant increase in total N and higher leaf chlorophyll content of the host plants. The rhizobacteria tested especially CCM 3863 had enhanced primary root numbers and length compared to the control (+Ni). All of the inocula tested successfully colonized the root-surface and benefit the host plants.