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Effects of aeration and nitrogen supply on cotton growth in solution culture

S. Kraokaw, F.P.C. Blarney, and S.A. Waring

Department of Agriculture, The University of Queensland, Brisbane QLD 4072

Cotton (Gossypium hirsutum L.) is sensitive to waterlogging under field conditions (3). Poor growth of crops has resulted from poor oxygen (02) supply, reduced nitrogen (N) availability through denitrification, and decreased uptake of N and of other nutrients through impaired root function (2,4). The relative importance of these factors has not been established for cotton.


A solution culture experiment was conducted in 22.2 L sealed pots in which cv. Deltapine 90 was grown for 21 d under well-aerated conditions at three N levels. An optimum N supply (Nor) was estimated and supplied using the Programmed Nutrient Addition technique (1), and N was supplied also at one half (0.5Nopt) and twice (2Nopt)this rate. Four aeration treatments were then imposed for 12 d, by bubbling air (c. 21% 02) or a mixture of 02 and N2 gases at 5, 2 and 0% (v/v) 02 through the solutions. The dry mass of plant parts, total dry mass and the plant nutrient status were determined at the beginning and end of the aeration period.

Results and discussion

At Day 21, the total dry mass of plants increased with increased N supply, from 1.38 to 2.46 g/ plant. Likewise, the N concentration in the leaf increased from 3.14 to 4.28%, but that of phosphorus (P) was unaffected (mean of 0.27%). The equilibrium 02 concentration in solution decreased in treatments with 5, 2 and 0% 02 to < 5% (v/v) within 4 d of the start of the aeration treatments, and remained at this concentration for the duration of the experiment. The lower leaves of poorly-aerated plants became chlorotic, particularly in those plants of low N status. At the final harvest, the N concentration in plant parts was reduced by low N supply. Poor aeration reduced the N concentration in leaves from 4.46% at 21% 02 to 3.05% at 0% 02. The P concentration in plant parts was decreased by poor aeration, that in the leaf being reduced from 0.43 to 0.25% at the highest and lowest 02 concentrations. Increased N supply also decreased the P concentration in the plant. The leaf area of plants supplied with 2 and 0% 02 was decreased by c. 30% compared with those supplied with 21 and 5% 02. Poor aeration reduced the relative growth rate of plants by up to 20% at all levels of N supply. The rate of N uptake was 18.6 mg/ g N root dry mass/d with good aeration and at 2Nopt being reduced by 50% through poor aeration; low N supply resulted in a further reduction of c. 50%. The rate of P uptake at 0.5Nopt was reduced also by more than 50% through poor aeration, being reduced also with increased N supply. It appeared that the uptake rates of N and P were more sensitive to poor aeration than was plant growth per se. Thus, in soils, waterlogging might reduce cotton growth through decreased N supply (through denitrification) as well as through decreased N and P uptake (through poor 02 supply to the roots).


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Reicosky, D.C., Meyer, W.S., Schaefer, N.L. and Sides, R.D. 1985. Agric. Water Mgt 10, 127-143.

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