Five sites representing the main cotton growing soil types in the Lower Macquarie Valley were selected and soil sampled in late October and May 2004. Field selection was based on being a representative irrigated cotton soil of the Macquarie Valley as well as irrigation water source. One of the sites sources irrigation water from a moderately brackish (1.0 dS/m) bore. Three sites are supplied by schemes and the other by a river pump.

The pattern of measured is consistent with previous reports, the lighter red soils have significant higher deep drainage rates than the heavier grey soils. The increased drainage under the site irrigated with the saline bore (Bw) may be due to an electrolytical effect in which high EC water partially flocculates the soil and increases deep drainage (Beecher 1992).

The upper 50 cm of the meander plain soil (Bw ) became sodic (ESP greater than 5%) after irrigation compared to the pre irrigated samples. There was no significant change in the Na content the back plain soils due to the 2003-04 irrigation season (Ya, Dr). This result suggests that irrigation during the 2003-04 season on the lighter meander plain soils increased the risk of sodicification of these soils while there was no such effect on the heavier back plain soils.

The change in soil salt stored was calculated and the results show that all sites increased the salt store over the observation period (Fig. 6). The biggest increase occurred on the meander plain soils irrigated with the bore. At this site an additional 3.5 t/ha of salt was stored in the top 2.1 m. This estimate does not account for any effect of leaching by winter rainfall. Previous studies (Friend 2000) showed that winter rainfall has a significant effect on the amount of deep drainage and hence leaching of salts. Again it would be difficult to draw too many conclusions without undertaking additional post winter sampling.

Long term farm soil and water data has been collected and collated for one site. Some historical yield data has also been collected. The yield data was used to pinpoint areas of high and low yield. Initial analysis of the soil data in conjunction with yield maps suggests that areas of low yield also have high sub soil nitrates present after harvest. This suggests that the plant did not or could not access the nutrients. The finding has enabled the grower to eliminate nutrition as a factor in yield. The grower has identified these areas of low yield and high sub soil nitrates as areas of restricted infiltration.

The objective of development of a detailed research proposal that meets alternative funding bodies priorities was not achieved. The original plan was to approach the CW CMA and CRC IF for additional funding. The CW CMA is still being established and the investment plan has yet to be finalised, while the CRC IF will only fund post graduate studies. It is hoped that the CMA will be operational in the later part of 2004 or early part of 2005 and this will allow negotiation of a research agreement