|Jiang, T - CHANGQING KEY LAB, CHINA|
|Teng, L - SOUTHWEST UNIV, CHINA|
|Wei, S - SOUTHWEST UNIV, CHINA|
|Deng, L - SOUTHWEST UNIV, CHINA|
|Chen, Y - SOUTHWEST UNIV, CHINA|
|Luo, Z - SOUTHWEST UNIV, CHINA|
Submitted to: Journal of Environmental Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 7, 2010
Publication Date: July 1, 2010
Repository URL: http://hdl.handle.net/10113/44597
Citation: Jiang, T., Teng, L., Wei, S., Deng, L., Chen, Y., Luo, Z., Flanagan, D.C. 2010. Application of Polyacrylamide to Reduce Phosphorus Losses from 9 Chinese Purple Soil: A Laboratory and Field Investigation. Journal of Environmental Management. 91(7):1437-1445. Interpretive Summary: Phosphorus (P) is an important plant nutrient applied to crops as a fertilizer. However, it can also be a pollutant of off-site water bodies when it leaves fields via surface runoff or subsurface drainage. The P in the water can then stimulate excessive algae growth in rivers and lakes, and when the algae dies and decomposes it causes low dissoved oxygen levels in the water and subsequent death of fish and other water dwelling animals. This study examined a way to possibly reduce P losses by use of a chemical called polyacrylamide, or PAM, applied to the soil. When PAM was mixed into a soil column, it was able to reduce P losses in water draining downwards through the soil by 36%. In a field experiment where the PAM was broadcast on the soil surface alone and in combination with lime and gypsum, the chemical amendments were all able to reduce runoff and P losses in runoff. The PAM combined with lime or gypsum was both more effective than the PAM alone in reducing runoff and phosporus losses in runoff. However, wheat growth on the test plots was greatest where PAM alone had been applied, and less where the PAM with lime or gypsum were used. This research impacts farmers, landowners, conservation agency personnel, and others interested in methods to reduce agricultural pollution of off-site water bodies while maintaining crop yields. PAM can be used to reduce losses of P both in subsurface drainage water as well as in surface runoff.
Technical Abstract: The application of anionic polyacrylamide (PAM) for the control of phosphorus (P) losses from a steeply sloping Chinese purple soil was studied in both a laboratory soil column experiment and a field experiment. The results showed that PAM has an important inhibitory impact on vertical P transport in soil column experiment. The increased effect for controlling vertical P transport was unequivocal and the maximum experimental 0.2% PAM treatment was optimal. This treatment decreased soluble P concentration in the leachate by 38% and soluble P losses by 36%, compared to the control (CK). Additionally, cumulative P in the leachate solution was linearly related to elapsed time (R2>0.99), while cumulative P losses decreased as PAM dosage increased. In the steeply sloping (15o) field experiment, the effects of PAM application with and without addition of lime or gypsum were examined. The average runoff volumes from the PAM, PAM+CaCO3, and PAM+CaSO4 treatments were 61%, 61% and 66% of the control, respectively, and average leached volume ranged from 30% to 40% of the control with no differences between the three PAM treatments. Meanwhile, average total phosphorus (TP) losses in runoff were 45%, 24% and 22% of CK, respectively, with the PAM combinations having significantly greater effects than the PAM alone. This indicates that application of PAM alone and PAM plus a calcium source (PAM+CaCO3, PAM+CaSO4) on purple soil could be used to decrease the runoff and leaching volumes, as well as TP losses in runoff. However, the PAM treatments did not significantly affect the TP losses from leaching, most likely because of the low PAM soil surface application rate (3.9 kg.ha-1). In the field trials, five plant growth indexes (wheat plant height, leaf length, leaf width, grain number per head, and dried grain mass) were measured, and these results showed that the PAM mono-application resulted in the greatest wheat growth, while the two PAM combination treatments decreased wheat growth compared to the control. Thus, the specific conditions at a given location and the most desired or critical effect of PAM application should be considered before deciding the type of PAM combination to use.