Slide #2 is an image of water near begining of control furrow inflow showing no algae accumulating and a second image of water near begining of PAM treated furrow inflow showing algae accumulating.

In irrigation studies conducted a few years ago, we noticed that when irrigating with water that had been stored in a pond for several days prior to irrigation, furrows treated with PAM to reduce erosion, rapidly (1 - 2 hrs) accumulated algae tufts at the bottom of the furrows, whereas untreated furrows did not. This observation led us to speculate that PAM might be used to intentionally sequester microorganisms from water flowing down furrows.

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Slide #3

Scanning electron micrographs (SEMs) of soil in furrows treated with irrigation water containing PAM were made in this same field (Courtesy Craig Ross, Landcare New Zealand).  The SEMs show the untreated soil particles on the left, and the PAM-treated soil particles on the right.  The left image shows a diatomaceous "skeleton" from algae in the irrigation water.  The PAM applied via the irrigation water to soil (in the image at the right) is the netlike material covering the soil particles; this image provides a clear look at how PAM holds soil in place in treated furrows.  These images are from an area just below the furrow inflow point and, in the case of the PAM-treated furrow, would represent a higher than average PAM coverage than would be expected in the lower reaches of the furrow.

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Slide #4

Objective We determined the efficacy of polyacrylamide (PAM) to filter soil microorganisms in irrigation water within an agricultural field.

Slide #5

Study Design
Treatments:	Control
	PAM (Patch)
Reps:	3
Dates / Flow Rate:	6-19-97	2 gpm
	7-02-97	3 gpm
	7-17-97	4 gpm
Time:	30 min, 210 min and 390 min

Slide #6

Polyacrylamide Application The polyacrylamide used was a dry granular material having a molecular weight of 12-15 million g / mole with a 18% negative charge density. We spread 15 g of PAM on a 0.1 square meter area in the furrow 1 meter down slope of the water inflow point.

Slide #7

Sediment and Water Monitoring Advance duration Periodic measurements: inflow outflow sediment concentration Field length:  40 meters

Slide #8

Bio Sampling active fungi active bacteria total fungi total bacteria algae

Slide #9

Microbial Analysis Active and total microbial biomass were determined using direct counts with FDA and epifluorescent microscopy.

Slide #10

This is an image showing the erosion and turbidity occurring in a non-treated control furrow.

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Slide #11

This is an image of a PAM-treated furrow.  Note the clarity of the flowing water and the mats of floating algae which were promoted by PAM's ability to flocculate solids.  We rarely see algae mats in PAM treated furrows.  They were common in this study because the water source was from a pond where irrigation water was stored for several days before application.  Under these conditions, algae blooms occur in the storage pond, sometimes enough to give the water a pale green cast.  With such a greatly enlarged algae population in the water, the flocculating effect of PAM can produce these mats.  As our data will show below, other organisms are also removed from the water, some of them, undoubtedly also contained in these mats, or adhering to the furrow-bottom and furrow-sides.

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Slide #12

Sediment Loss (kg ha-1)
Trtmt	7.5 L/min	15.5 L/min	21.5 L/min
Control	85 a	5,250 a	11,291 a
PAM	54 a	163 b	280 b
Inflow (< 0.1)

As the table in this slide indicates, sediment loss greatly increased in controls as flow rates were progressively increased from 2 to 3 to 4 gallons per minute (7.5, to 15.5 to 21.5 liters per minute).  PAM treatment greatly reduced sediment loss, especially at the higher flow rates, where the reductions were statistically significant (5% level of probability).

Slide #13

Infiltration (mm)
Trtmt	7.5 L/min	15.5 L/min	21.5 L/min
Control	43 a	58 a	108 a
PAM	28 a	42 b	109 a

Infiltration is difficult to measure using the inflow/outflow difference method on furrows that are this short (40 meters, or 120 feet).  The data on this slide merely confirm that PAM's reduction in sediment loss was due to changes in sediment concentration, not reductions in runoff amount.  In a large body of work on production-sized fields (typically ten or more times this furrow length), PAM has typically shown to increase infiltration about 15% on this soil.

Slide #14

Algae ( µg C ml-1 H2O)
Trtmt	Dist, m	7.5 L/min	15.5 L/min	21.5 L/min
Control	1	10.4 cd	25.3 cd	516.9 a
PAM	1	2.5 d	2.5 d	599.5 a
Control	40	64.4 c	58.3 b	659.0 a
PAM	40	5.3 d	5.3 d	72.7 bc
Inflow (321.9 b)

Algae content of the runoff water was not statistically affected at the 1 meter field sampling point but was statistically reduced at all three flow rates at the 40 meter sampling point.  This suggests that some mixing time was required to enable the PAM effect.

Slide #15

Active Fungi ( µm hyphae x104 ml-1 H2O)
Trtmt	Dist, m	7.5 L/min	15.5 L/min	21.5 L/min
Control	1	0.3 f	20.8 c	229.9 a
PAM	1	0.3 f	9.3 cd	60.0 b
Control	40	3.7 e	41.7 bc	183.6 a
PAM	40	0.0 f	4.6 e	18.5 c
Inflow (0.0 f)

Active fungi were unaffected at the one meter sampling point in the two lower inflow rates, but were significantly reduced by PAM at the highest inflow rate even at 1 meter.  At the 40 meter sampling point fungi were reduced at all three inflow rates.

Slide #16

Total Fungi ( µm hyphae x104 ml-1 H2O)
Trtmt	Dist, m	7.5 L/min	15.5 L/min	21.5 L/min
Control	1	265 b	827 a	827 a
PAM	1	0.0 d	215 b	215 b
Control	40	360 b	826 a	715 a
PAM	40	0.0 d	32 c	31 c
Inflow (0.00 d)

Total fungi were significantly reduced at all flow rates and at both sampling points along the furrow.  Reductions were more dramatic at the higher flow rates at the 40 meter sampling point, further suggesting that greater mixing may enhance the effect.

Slide #17

Active Bacteria (bacteria x105 ml-1 H2O)
Trtmt	Dist, m	7.5 L/min	15.5 L/min	21.5 L/min
Control	1	12.4 e	80.4 c	234.9 a
PAM	1	2.3 f	25.7 d	145.4 b
Control	40	10.6 e	81.3 c	299.3 a
PAM	40	2.9 f	26.3 d	133.2 b
Inflow (3.9 f)

Active bacteria were significantly reduced by PAM at both sampling points and all inflow rates.

Slide #18

Total Bacteria (bacteria x105 ml-1 H2O)
Trtmt	Dist, m	7.5 L/min	15.5 L/min	21.5 L/min
Control	1	12.8 c	13.9 c	41.2 b
PAM	1	12.9 c	6.3 d	33.0 b
Control	40	22.8 b	30.5 b	96.5 a
PAM	40	12.1 c	12.1 c	39.8 b
Inflow (15.8 c)

Total bacteria were not consistently affected by PAM treatment at the one meter sampling point.  Total bacteria were reduced for the 3 gpm (15.5 liter per minute) inflow rate at one meter, but not the lowest or highest inflow rates.  At the 40 meter sampling point, total bacteria were reduced by PAM treatment for all three inflow rates, again suggesting that mixing improved PAM efficacy.

Slide #19

Active Microbes ( µg C  ml-1 H2O)
Trtmt	Dist, m	7.5 L/min	15.5 L/min	21.5 L/min
Control	1	0.15 fg	2.02 cd	8.75 a
PAM	1	0.06 g	0.82 ef	6.67 ab
Control	40	4.19 cd	2.47 cd	7.21 a
PAM	40	0.11 fg	0.62 ef	3.00 bc
Inflow (0.75 ef)

Active microbes were not consistently affected by PAM treatment at the one meter sampling point.  Active microbes were reduced for the 3 gpm (15.5 liter per minute) inflow rate at one meter, but not the lowest or highest inflow rates.  At the 40 meter sampling point, total bacteria were reduced by PAM treatment for all three inflow rates, again suggesting that mixing improved PAM efficacy.

Slide #21

Conclusions:  Microbial Study PAM reduced outflow loss of all classes of microorganisms observed. Reductions were typically 50-90% (factor of 2 to 10). Microorganisms increased along the furrow length with controls and PAM-treatment, but there was a relatively larger decrease in microbes from PAM-treatment with distance.

Slide #22

Conclusions PAM can effectively sequester biological contaminants of runoff water while controlling erosion. Phytopathogen epidemiology and control impacts can be expected to be substantial as well as impacts on public health status of irrigation return flows.

Slide #23

Discussion PAM could potentialy be used to manage: harmful organisms from animal waste in runoff and groundwater. plant pathogens such as Phytophthora sp, spread in runoff and groundwater.

Slide #24

Our final photo is a split image comparing a non-treated irrigation furrow with water running, showing typical erosion and turbidity next to a PAM-treated furrow with no erosion and clear water.  An insert shows water samples withdrawn from the outflow of each field; the untreated outflow is turbid and heavily laden with suspended sediments; the sample of PAM-treated outflow is nearly as clear as tap water.  This photo is a testament to PAM's potential for erosion control and runoff water quality protection.  Feel free to email us to request more information or to request answers to specific questions.

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