United States Department of Agriculture United States Department of Agriculture - Agricultural Research Service Agricultural Research Service
Northwest Irrigation & Soils Research Lab,  Kimberly, ID
 
Massey University, New Zealand

Use of PAM to Control Erosion From Raised Beds Under Sprinkler Irrigation

D.J. Horne1, R.E. Sojka2, D.L. Bjorneberg2 and J.A. Foerster2

1Massey University, New Zealand
2USDA Agricultural Research Service, Northwest Irrigation and Soils Research Laboratory, Kimberly, Idaho


Introduction

The movement of soil from raised beds, as used to grow crops such as potatoes, and the associated slumping and degradation of beds is often a serious problem under sprinkler irrigation. Polyacrylamide (PAM) has proven very successful at mitigating similar problems in furrow irrigation. The objective of this study was to investigate the potential of PAM to control erosion and minimise damage to raised beds under sprinkler irrigation.

Soil erosion.

Method

Soil was placed in a series (6) of boxes (1.2 x 1.5 m) and ridged to resemble raised beds. The boxes were irrigated by an overhead sprinkler.

   Treatments

Three of the boxes were irrigated with water and 3 were irrigated with PAM solution.

   Soils

Two contrasting soil types were used - a medium textured soil (Portneuf silt loam) and a fine textured soil (Roza silty clay).

   PAM

Each soil was irrigated 4 times: irrigation events were approximately one week apart.
The 1st irrigation - PAM was applied at 3 kg ha-1 i.e. a 15 ppm solution was irrigated for 15 mins at 80 mm hr-1.
The 2nd 3rd and 4th irrigations - PAM was applied at 0.66 kg ha-1 i.e. a 5 ppm solution was irrigated for 10 minutes.
 
Soil Beds with infiltrometer.

Results

  • PAM had a very marked impact on sediment loss. Compared with water irrigation, PAM reduced soil loss by 85 to 95% for the silt loam and by 70 to 80 % for the silty clay.
  • Approximately 50% more of the PAM treated water infiltrated into the ridges than was the case for water (see Figure)
  • Infiltration rates (at 100 and 40 mm tension) of ridges irrigated with PAM solution were approximately double the rates of ridges irrigated with water (see Table, differences between treatments are significant at P=0.05).
  • Soil irrigated with PAM had approximately 20% more water stable aggregates than soil irrigated with water (P= 0.05).
Change in volumetric moisture content of ridges of silty clay.
Change in volumetric moisture content of ridges of silty clay.

 

Infiltration Rates (mm hr-1) Following Irrigation (event No. 4)
Portneuf silt loam
Treatment 100 mm 40 mm
Water 22 30
PAM 38 61
Roza silty clay
Water 12 21
PAM 30 40


Conclusions

By protecting soil structure, PAM significantly improved irrigation efficiency on both soils i.e. with PAM, there was less water and sediment runoff, less slumping of the raised bed profile, increased wetting of the raised bed, increased infiltration rates, and enhanced aggregate stability. The results presented here suggest an important role for PAM in sprinkler irrigation of raised beds.

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