Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Titre : Improving efficiencies of nitrogen and water use for rice in semi-arid tropical Australia

Auteur : Borrell, Andrew Kenneth

Université de soutenance : University of Queensland

Grade : Doctor of Philosophy (PhD) 1994

Résumé
The cost of producing rice in north Queensland is high. Nitrogen (N) fertiliser and irrigation water account for about 20 and 40%, respectively, of total variable production costs in both wet and dry seasons. Therefore improving the efficiencies of N and water use were high priorities of the rice industry.

Studies were undertaken to improve the efficiencies of N and water use for rice production in semi-arid tropical Australia. Experiments were conducted in the Burdekin River Irrigation Area (BRIA) (20o03’S, 147o17’E). The aim was to maximise grain yield by optimising its functional components : (level of resource) x (resource use efficiency) x (harvest index, HI). Grain yield was analysed in terms of (N content) x (NUEtdm) x (HI) in the N studies, and in terms of (water use) x (WUEtdm) x (HI) in the irrigation studies, where NUEtdm is nitrogen use efficiency (total above-ground dry mass per total N content), and WUEtdm is water use efficiency (total above-ground dry mass per water applied via irrigation and rainfall).

In the first set of experiments, the effects of season (wet and dry), N rate (0, 70, 140, 210 and 280 kg ha’1) and plant type (maturity and stature) on N content, NUEtdm and HI were examined in two wet and two dry seasons between 1986 and 1988. The genotypes used were Lemont (early-maturing, shortstatured), Newbonnet (early-maturing, medium-statured), 83-25-3 (late-maturing, short-statured) and Starbonnet (late-maturing, tall-statured). In the second set of experiments, the effects of season and irrigation method (three flooded and two unflooded methods) on water use, WUEtdm and HI were examined in Lemont during the 1989 dry and 1990 wet seasons. In addition, the effect of irrigation method in rice on the phosphorus (P) and zinc (Zn) nutrition of upland crops following rice was examined in the 1990 wet season using soybean, and in the 1990 dry season using maize.

The successful growth of soybeans under saturated soil culture (SSC) in northern Australia suggested that this technique may be adapted to rice production in north Queensland. SSC involves the growth of plants on raised beds with water maintained in the furrows between the beds. The irrigation studies compared the growth under SSC with four alternative irrigation systems : permanent flood at the 3-leaf stage (traditional method, PF-3L), permanent flood at sowing (PF-S), permanent flood at panicle initiation (PF-PI) and intermittent irrigation at weekly intervals throughout crop growth (II).

Présentation