In 2005-06 we began investigations comparing the yield and maturity response of 38 cm (15') row spacings and conventionally spaced cotton while attempting to manage the two row spacings for Pix and nitrogen management separately. The 38 cm row spaced cotton did not need to be managed differently to the conventionally spaced crop in any of the three experiments for this season. In one of the three experiments the 38 cm spaced cotton had higher yield than conventionally spaced cotton. Research is continuing to understand how 38 cm row spaced cotton systems can be managed to give yield or maturity benefits.

Surface irrigation, especially furrow irrigation, is one of the most commonly used methods for irrigating crops and pastures in Australia and around the world. Well-designed and managed surface irrigation systems can have application efficiencies of up to 95%. But many commercial systems have been found to be operating with lower and highly variable efficiencies. For example, in sugar and cotton application efficiencies for individual irrigations range from 14 to 90% and average efficiencies over the season range from 31 and 62% (Raine and Bakker 1996; Smith et al. 2005).

This study evaluates the physiological responses of fourteen cotton genotypes under waterlogged and non-waterlogged irrigated conditions in relation to leaf nutrient level, leaf colour, leaf photosynthesis, plant morphology and final yield.

BollgardII accumulated yield faster than conventional cotton due to higher retention combined with a very low proportion of tipped plants. This meant that late in flowering and at cut-out BollgardII was less able to compensate for water stress equal to a depletion of =120mm of soil water (= 58% plant available soil water) and yields were lower relative to conventional cotton stressed at the same time., *Yields and soil water extraction of BollgardII and conventional cotton were the same when moisture stress occurred at early flowering., *With full irrigation, that is soil water deficits of 44 to 83 mm, BollgardII had the same yield or higher yield than conventional cotton but matured earlier due to more rapid boll setting., *Future research will aim to optimise irrigation scheduling of BollgardII for yield and water use efficiency

Soil moisture extraction under fully irrigated conditions was the same in BollgardII and conventional varieties, except where season length allowed later crop and leaf growth in the conventional variety. *BollgardII grown under fully irrigated conditions maintained a yield advantage and required 6.3ML/ha of irrigation water as opposed to 7.0ML/ha for the conventional full irrigation treatment. *A greater reduction in water use efficiency was apparent in BollgardII where moisture stress was experienced at or close to cut-out, except where late season rainfall alleviated this stress.

This pilot experiment at Carroll and Narrabri investigated the yield and fibre quality benefits of application of foliar potassium, phosphorus and micronutrients to a high yielding Bollgard II and Roundup Ready variety.

Waste-stream materials can be obtained at little or no cost but their value in agriculture is limited by transportation and application costs. To be practical and economic, waste products must be applied on agricultural land which should be located near the production facility. In this study we examine the effects of a wide range of organic amendments on cotton soil and the associated changes due to their application. If application of these materials proves beneficial, it will benefit not only cotton farmers but will also offer an economic and environmentally acceptable means of waste disposal.

Our research group set out to examine three topics: we documented the diversity of common microbes in cotton soils and followed this with research targeting interactions between microbes and seedling pathogens, we examined the impact of cultivation of cotton on diversity and abundance of AM fungi, and we commenced a study to determine the importance of microbes in sequestering carbon in soil.

Soil quality issues have been researched within a crop rotation experiment that started in 1994 at Narrabri. It compares three crop rotations that have included or excluded legume phases throughout this period. The data presented here relate to the most recent 2-year cycle of this experiment. Following cotton harvest in all three rotation systems in May 2004, oats was sown in two systems. Following oat harvest, the soil was either left fallow (oat-fallow treatment) or vetch was sown in the April 2005 and green-manured in August 2005 (oat-vetch treatment). In the third treatment, vetch was planted in May 2004, green-manured in August 2004 and cotton sown in October 2004, vetch was sown in May 2005 and green-manured in August 2005 (vetch-cotton-vetch treatment). Cotton (cv Sicot 71BR) was sown in October 2005 across all systems.

The way the cotton plant responds to water stress on different soil types changes will influence its requirement for water and may change the irrigation strategy used if yield potential is to be achieved. Soil types are different not only in the total amount of available moisture that they hold, but also in how readily the moisture is made available to the plant. This response has been investigated in a three year project measuring plant water stress under different irrigation conditions during early flowering on three soil types. Initial interpretation of results suggests that plants differ in their response to soil moisture stress on light soils compared with heavier soils, when using a standardized measurement of soil moisture status i.e. the fraction of transpirable soil water (FTSW). FTSW is calculated by changing available water content of the soil to a percentage. The advantage of using FTSW to define soil moisture holding capacity is that it allows people working across different known soil types to compare soil types in terms of irrigation schedule and plant moisture availability.