Trois publications ont été présentées par des chercheurs du Programme lors de la conférence du IAPSIT qui s'est enue en Inde en Novembre 2011.

• Evolution of the agronomic and environmental phosphorus status of soils in Mauritius after seven year sugarcane crop cycle.
  par T.Mardamootoo; K.F. Ng Kee Kwong;C.C.Du Preez
• Pollen studies in Erianthus aroundicaneaous, saccharum officinarum and commercial S.officirarum clones
  par S.S. Sattar; M.Khrishuamurthi;J.S Gawander
• Baseline climatology of four sugar mill stations in Fiji and current climatic trends
  par J.S Gawander; M.Lal; P.Rounds

 Evolution of the agronomic and environmental phosphorus status of soils in Mauritius after seven year sugarcane crop cycle.

T.Mardamootoo; K.F. Ng Kee Kwong;C.C.Du Preez

Abstract

The intensive application of P fertilisers in sugarcane production has probably resulted in P levels which could be of concern to freshwater quality in Mauritius.  Only very small amounts of P must be lost from the soil to create a P concentration in freshwater ecosystems likely to cause eutrophication. To prevent eutrophication, total P should not exceed 0.05 mg L-1 in streams entering lakes/reservoirs as per directives of the United States Environmental Protection Agency. For this reason, the scope of the current agronomic soil P test (using 0.1M  H2SO4 as extractant) was broadened to be used also in the evaluation of the environmental P status of soils for freshwater protection in Mauritius. The environmental threshold was determined by establishing the relationship between 0.01M CaCl2 and 0.1M H2SO4 extractable P. It was inferred that above 85 mg kg-1 0.1M H2SO4-P, the soil P represents a potential risk for contamination of runoff waters. The number of fields with unacceptably high levels of P (P ≥ 95 mg kg-1) increased from 42% to 53% in just one crop cycle of sugarcane. In 2005/2006 more that 50% of the sugarcane soils had an unsafe environmental soil P status and the majority of the sugarcane fields with an environmentally unacceptable soil P levels were located on the two latosolic soil groups. Hence revision of P management practices or implementation of other corrective measures such as creation of riparian zones should primarily be directed towards those two soil groups.

Keywords: Corporate and small farmers, freshwater pollution, soil phosphorus test, soil groups

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 Pollen studies in Erianthus aroundicaneaous, saccharum officinarum and commercial S.officirarum clones

S.S. Sattar; M.Khrishuamurthi;J.S Gawander

Abstract

Sugar Research Institute of Fiji has been continuously engaged in developing parental lines with wider genetic base through inter-generic and inter-specific hybridization with Erianthus arundinaceous and Saccharum officinarum (Daniels 1963 internal report). The main objective is to develop high-yielding disease resistant varieties with wider adaptability. The combination of genes from various genera and species is possible only when pollination can be effected. Thus the anthesis time and pollen viability of Erianthus arundinaceous (wild cane), Saccharum officinarum (Badila), S.officinarum cultivar, Spartan and another cultivar LF02-48 were studied. Viability tests were carried out using invitro culture method (Krishnamurthi 1977).  Pollen was collected and cultured every hour for ten hours from the time of anthesis. The percentage tube growth showed that Erianthus arundinaceous retained its viability for three hours whereas S.officinarum Badila started to lose its viability within one hour. Spartan retained its viability for seven hours whereas LF02-48 started to lose its viability after two hours. The pollen viability for all four varieties tested dropped below 50% after six hours. Pollen from Erianthus arundinaceous was collected at six different times and tested for viability. It was found that pollen collected from the first anthesis had the highest viability. This paper presents the observations on pollen viability in relation to anthesis time.

Keywords: Erianthus arundinaceous, Saccharum officinarum, viability, anthesis, pollen, pollination

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Baseline climatology of four sugar mill stations in Fiji and current climatic trends

J.S Gawander; M.Lal; P.Rounds

Abstract

The purpose of this paper is to characterize observed behavior of surface climate at the four major sugar producing cane regions in Fiji (Lautoka, Rarawai, Penang and Labasa Mill areas) during the instrumental period and up to present, providing an impression of ongoing climate trends and how this might have affected exposure units of interest. The focus is on surface observations of air temperature and rainfall, although some information on South Pacific Ocean climate is also discussed, given its relevance for Fiji’s weather pattern. The variations in rainfall have a major impact on cane and sugar yields. However this paper would not deal in detail the impact of the sugarcane and sugar production trends with regard to weather.

A major comparative analysis of last fifty years of data with the baseline period from 1961 to 1990 was undertaken.  The findings suggest that the surface air temperatures have registered increasing trends at all the mills during the period 1961-2010. There has been a steady increase in the number of days per year with warmer nighttime temperatures in recent decade. The rise in annual mean surface air temperature over the four sites is highest at Labasa and the value is approximately 0.04oC over the  50-year period. 

No major trend has been observed at any of the stations on annual basis. However  interannual variability in annual as well as summer rainfall were observed at all the sites including the extreme rainfall which has decreased slightly during the  50-year period which may  be attributed to ENSO events and intra-seasonal oscillations in the mean position of South Pacific Convergence Zone.

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