2007 Annual Report - Central Queensland University

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2007 Centre for Plant & Water Science Annual ReportThe movement of the irrigation water front and the oxygen concentration (Pst-3 oxygensensitive mini-sensors) in the soil has been measured. The concurrent soil water content (usingthe capacitance-based Microgopher and EnviroScan systems) has been recorded in order toderive the water:oxygen ratio for optimum soil performance. Root density and distribution, andthe concentration of oxygen in the soil and its distribution around the soil-root interface and infront of the irrigation water front are being examined.On a per plant basis a portable IRGA has been used to quantify response of photosynthesis,transpiration and stomatal conductance. Canopy growth has been quantified through bothdestructive sampling and through measurement of light interception using the AccuPARceptometer (Decagon USA).PROJECT STAFF Investigators: Lance PendergastPrincipal Supervisor: Professor David MidmoreCo-Investigators: Associate Professor Kerry WalshDr Chris CarrollFUNDINGCentral Queensland University Postgraduate Research Award31

2007 Centre for Plant & Water Science Annual ReportTHE EFFECT OF EMITTER DEPTH ON CAPSICUM YIELD AND YIELDCOMPONENTSSUMMARYIn a pot experiment, capsicum was irrigated by subsurface drip irrigation with emitters placedat 5 cm or 20 cm below the soil surface. Statistical analysis on soil respiration rate, lightinterception, and shoot and root components showed that due to severe anaerobic conditionsprevailing in the deep treatment, the plants grown in the shallow treatment significantly outperformedthan those grown in the deep treatment.Capsicum seedlings were transplanted in 28 L buckets (30 cm in diameter and 40 cm high)containing black clay soil (FC=43 mm 100 mm -1 ), 43 days after sowing. Each bucket containedtwo plants irrigated by subsurface drip irrigation. Two treatments consisting of shallow emitterplacement (5 cm) and deep emitter placement (20 cm) were applied. Each treatment wasreplicated six times in three blocks. Soil moisture was maintained within 40 – 51 mm 100 mm -1 .Table 1 shows the result of this experiment. As can be seen from the table, soil respiration rateand light interception as well as root and shoot components under the shallow emitterplacement were significantly higher in comparison with the deep emitter placement. Onepossible reason is as follows: since no drainage flow could occur from the side or bottom of thebuckets, the expulsion of the soil air during irrigation events was only in the upward direction.For the deep treatment, flow of water from the middle of bucket would expel the soil airwithout any obstruction. In the shallow treatment, the layer of water flowing from top to thebottom of the bucket obstructed upward flow of the soil air. The serially entrapped air resultedin the better performance in the shallow treatment. Soil water distribution data are beingreviewed to confirm or otherwise.Table 1- Statistical analysis on the yield and yield componentsMean of the measured parametersSoilrespirationrate(g m -2 h -1 )Lightinterception(%)Sampledrootlength(cm/cm 3 )Averagediameterof thesampledroots(mm)Dryweight ofthesampledroots(g)Fruitcounts(-)Weightof freshfruits(g)Weightof freshleaves(g)Weightof freshstems(g)TreatmentShallowemitterplacement(55.0 L/pot)Deep emitterplacement(44.5 L/pot)0.61 55 11.71 0.34 0.40 20 2304 211.7 239.30.42 44 8.18 0.31 0.20 15 1422 124.1 126.9t test 0.05

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2007 Annual Report - Central Queensland University 2007 Annual Report - Central Queensland University