Enhancing the productivity of high‐magnesium soil and water resources in Central Asia through the application of phosphogypsum

Recent evidences from some irrigated areas worldwide, such as Central Asia, suggest that water used for irrigation contains magnesium (Mg²⁺) at levels higher than calcium (Ca²⁺). Excess levels of Mg²⁺ in irrigation water and/or in soil, in combination with sodium (Na⁺) or alone, result in soil degradation because of Mg²⁺ effects on the soil's physical properties. More than 30 per cent of irrigated lands in Southern Kazakhstan having excess levels of Mg²⁺ are characterized by low infiltration rates and hydraulic conductivities. The consequence has been a gradual decline in the yield of cotton (Gossypium hirsutum L.), which is commonly grown in the region. These soils require adequate quantities of Ca²⁺ to mitigate the effects of excess Mg²⁺. As a source of Ca²⁺, phosphogypsum—a byproduct of the phosphorous fertilizer industry—is available in some parts of Central Asia. In participation with the local farming community, we carried out a 4‐year field experiment in Southern Kazakhstan to evaluate the effects of soil application of phosphogypsum—0, 4·5, and 8·0 metric ton per hectare (t ha⁻¹)—on chemical changes in a soil containing excess levels of Mg²⁺, and on cotton yield and economics. The canal water had Mg²⁺ to Ca²⁺ ratio ranging from 1·30 to 1·66 during irrigation period. The application of phosphogypsum increased Ca²⁺ concentration in the soil and triggered the replacement of excess Mg²⁺ from the cation exchange complex. After harvesting the first crop, there was 18 per cent decrease in exchangeable magnesium percentage (EMP) of the surface 0·2 m soil over the pre‐experiment EMP level in the plots where phosphogypsum was applied at 4·5 t ha⁻¹, and a 31 per cent decrease in EMP in plots treated with phosphogypsum at 8 t ha⁻¹. Additional beneficial effect of the amendment was an increase in the soil phosphorus content. The 4‐year average cotton yields were 2·6 t ha⁻¹ with 8 t ha⁻¹ phosphogypsum, 2·4 t ha⁻¹ with 4·5 t ha⁻¹ phosphogypsum, and 1·4 t ha⁻¹ with the control. Since the amendment was applied once at the beginning, exchangeable Mg²⁺ levels tended to increase 4 years after its application, particularly in the treatment with 4·5 t ha⁻¹ phosphogypsum. Thus, there would be a need for phosphogypsum application to such soils after every 4–5 years to optimize the ionic balance and sustain higher levels of cotton production. The economic benefits from the phosphogypsum treatments were almost twice those from the control. Copyright © 2007 John Wiley & Sons, Ltd.     

Water ‘banking’ in Fergana valley aquifers—A solution to water allocation in the Syrdarya river basin?

The Syrdarya river is an example of a transboundary basin with contradictory water use requirements between its upstream and downstream parts. Since the winter of 1992-93, the operational regime of the upstream Toktogul reservoir on the Naryn river - the main tributary of the Syrdarya - has shifted from irrigation to hydropower generation mode. This significantly increased winter flow and reduced summer flow downstream of the reservoir. Consequently, excessive winter flow is diverted to the saline depression called Arnasai, while water for summer irrigation is lacking. This study suggests to store the excessive winter flows temporarily in the upstream aquifers of the Fergana valley and to use it subsequently for irrigation in summer. It is estimated that groundwater development for irrigation could be practiced on one-third of the irrigated land of the valley, and conjunctive use of groundwater and canal water on another third; the rest will remain under canal irrigation. This strategy will lower the groundwater table and create aquifer capacity for temporal storage of excessive water—“water banking”. This use of the term is only one of many concepts to which “water banking” or “groundwater banking” is applied. In this paper, the term is applied for temporary storing of river flow in subsurface aquifers. Pilot modeling studies for the Sokh aquifer - one of the 18 aquifers of the Fergana valley - supported that this strategy is a feasible solution for the upstream-downstream issues in the Syrdarya river basin. Field studies of water banking are required to determine the scale of adoption of the proposed strategy for each aquifer of the Fergana valley.     

Mutagenic treatment of microspore-derived embryos of turnip rape (Brassica rapa) to increase oleic acid content

The article presents the results of a study on obtaining mutant doubled haploids of turnip rape. The culture medium for producing embryos in isolated microspore culture was optimized. The optimal medium formula was NLN + 13% S + 0.05 mg/L NAA + 0.05 mg/L BA. Embryos derived from isolated microspore culture were treated with EMS mutagen in three concentrations (4 mM, 8 mM, and 12 mM). Mutant doubled haploid plants and their seeds were obtained. Agronomic evaluation and analysis of fatty acid composition in mutant lines seeds showed that they had valuable traits in terms of seed oil quality and yield. Analysis of the fatty acid composition of the seeds of the obtained mutant doubled haploids showed an increase in the percentage of oleic acid (~11%–12%) in comparison with donor cultivars. Our results showed that mutagenesis of embryos from a culture of isolated microspores has potential for improving the qualitative traits of turnip rape.