**3. Results and discussion**

Effluent water analysis showed that sulfate (182 mg L−1), bicarbonate (125 mg L−1), chloride (120 mg L−1) and sodium (101 mg L−1) are the most dominant elements in the water (**Table 1**).

On average, soil pH was 6.9 at the initiation of the study (**Figure 1**). ANOVA test showed no changes in pH for 9 years after using effluent water (**Figure 1**). These results are similar to the findings in a previous study on the fairways of the same golf course [9]. These results likely were due to the use of sulfur (S) burner units on the golf course irrigation system. After transitioning to effluent water, the Heritage Golf Course installed a sulfur burner. Sulfur burner units heat elemental S to create sulfurous acid for injection into irrigation water to reduce the bicarbonate content and pH [7]. The fact that we did not see an increase in soil pH suggests that the S burner was effective in controlling soil pH associated with effluent water irrigation. Soil pH increases have been observed by others in soils under effluent water irrigation [7, 17]. At this site, soil pH was maintained without change over 9 years by reducing the bicarbonate level in the irrigation water and releasing H+ into water and soil.

The SOM was significantly different among the sampling years with the means linearly increasing from 1999 to 2009 (**Figure 2**). Comparing before using effluent water (1999) and after 9 years of using effluent water (2009) at the Heritage Golf course, we found that SOM significantly increased (R<sup>2</sup> = 0.83). At the initiation of the study in 1999, SOM content was 0.12%, which increased to 1.5% in 2009. The average increase was 0.15% annually. To calculate the total carbon (C) sequestration from SOM, an assumption was made that SOM contains 58% C, and putting greens have 1.6 g cm−3 bulk density. The average annual total C sequestration was 1.4 t h−1 yr−1 during 9 years of using effluent water. Our calculation for this site was higher than the estimation that was reported by Qian and Follett [18] that soil C sequestration rate was 1.1 t h−1 yr−1 on golf course putting greens. Soil organic matter is a significant component in turfgrass systems; it affects soil porosity, water and nutrients retention, and percolation in the sand-based root zone. In addition, the calculation of C sequestration from SOM could be helpful to understand the role of turfgrass systems in storing C in the soil.


**Table 1.** Effluent water quality used in Heritage Golf Course (season average).

organic matter was determined by reaction with Cr<sup>2</sup>

2− is titrated with FeSO4

dizable organic matter was calculated by the difference in Cr<sup>2</sup>

unreacted Cr2

**2.2. Data analysis**

water for irrigation.

**3. Results and discussion**

level in the irrigation water and releasing H+

O7

80 Arid Environments and Sustainability

ally by SOM decomposition.

O7

[15]. Estimated N release is calculated to determine the potential amount of N released annu-

Data were analyzed by analysis of variance (ANOVA) [16] to test the effect of irrigation with effluent water on individual soil chemical properties. Comparisons between years were examined, and means were separated by LSD at 0.95 level of confidence. Regression analysis was used to examine the changes in individual soil parameters over time after the use of effluent

Effluent water analysis showed that sulfate (182 mg L−1), bicarbonate (125 mg L−1), chloride (120 mg L−1) and sodium (101 mg L−1) are the most dominant elements in the water (**Table 1**). On average, soil pH was 6.9 at the initiation of the study (**Figure 1**). ANOVA test showed no changes in pH for 9 years after using effluent water (**Figure 1**). These results are similar to the findings in a previous study on the fairways of the same golf course [9]. These results likely were due to the use of sulfur (S) burner units on the golf course irrigation system. After transitioning to effluent water, the Heritage Golf Course installed a sulfur burner. Sulfur burner units heat elemental S to create sulfurous acid for injection into irrigation water to reduce the bicarbonate content and pH [7]. The fact that we did not see an increase in soil pH suggests that the S burner was effective in controlling soil pH associated with effluent water irrigation. Soil pH increases have been observed by others in soils under effluent water irrigation [7, 17]. At this site, soil pH was maintained without change over 9 years by reducing the bicarbonate

into water and soil.

The SOM was significantly different among the sampling years with the means linearly increasing from 1999 to 2009 (**Figure 2**). Comparing before using effluent water (1999) and after 9 years of using effluent water (2009) at the Heritage Golf course, we found that SOM significantly increased (R<sup>2</sup> = 0.83). At the initiation of the study in 1999, SOM content was 0.12%, which increased to 1.5% in 2009. The average increase was 0.15% annually. To calculate the total carbon (C) sequestration from SOM, an assumption was made that SOM contains 58% C, and putting greens have 1.6 g cm−3 bulk density. The average annual total C sequestration was 1.4 t h−1 yr−1 during 9 years of using effluent water. Our calculation for this site was higher than the estimation that was reported by Qian and Follett [18] that soil C sequestration rate was 1.1 t h−1 yr−1 on golf course putting greens. Soil organic matter is a significant component in turfgrass systems; it affects soil porosity, water and nutrients retention, and percolation in the sand-based root zone. In addition, the calculation of C sequestration from SOM could be

helpful to understand the role of turfgrass systems in storing C in the soil.

2− and sulfuric acid. The remaining

2− before and after the reaction

using ortho-phenanthroline as an indicator, and oxi-

O7

**Figure 1.** Effect of using effluent water irrigation on soil pH. Different letters indicate significant differences using LSD (*P* < 0.05).

before using effluent water which was 4.6 kg ha−1 (**Figure 4**). Estimated N release is an estimate of N potentially released annually by decomposition of SOM. Estimated N release could be affected by many factors such as soil moisture, temperature, and soil type. This large increase was due to the fertilization and organic matter increase as well as substances added by effluent water because it often contains significant concentrations of organic nutrients, such as N and P [19]. Increases in this category were also a result of increased biomass production that translated to increases in SOM and eventually available N from organic matter decomposition.

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Soluble S increased over time (R<sup>2</sup> = 0.82; **Figure 5**). The percentage increase during the 9 years of using effluent water was 413%. As mentioned earlier, this increase of S content over time was a result of using S burner to inject elemental S into irrigation water to reduce pH and bicarbonate concentration in effluent water [7]. Turf managers at Heritage Golf Course encountered a problem of increased black layer beneath putting green surfaces since 2003. Black layer is the formation of a layer of metal sulfide [20, 21], which forms when hydrogen

sulfur-reducing bacteria (SRB). Black layer is typically associated with turfgrass chlorosis,

Soluble S is the substrate for S reduction activity that leads to black layer. Therefore, the use of a S burner under effluent water irrigation might have partially contributed to the increased occurrence of black layer. Further research is needed to address the potential relationship

In addition, extracted phosphates increased over time (R<sup>2</sup> = 0.83; **Figure 6**), and the percentage of increase during 9 years of using effluent water was 388%. This increase was expected because effluent water usually has more soil phosphates than freshwater. Increases in phosphates over

**Figure 4.** Effect of using effluent irrigation on soil's estimated N release. Different letters indicate significant differences

years of using effluent water irrigation have been recorded in previous studies [9, 22].

between the incidence of black layer and effluent water irrigation.

S) gas reacts with metal elements in the soil. Hydrogen sulfide gas is produced by

sulfide (H<sup>2</sup>

using LSD (P < 0.05).

wilting, thinning, and sometimes death.

**Figure 2.** Effect of using effluent water irrigation on soil organic matter. Different letters indicate significant differences using LSD (*P* < 0.05).

Putting greens had low CEC (1.9 cmol<sup>c</sup> kg−1) at the beginning of the experiment. This was because it was mostly sand with low SOM and contained low inorganic colloids. Soil CEC is increased by 174% over the course of the experiment (R<sup>2</sup> = 0.86) and by an average rate of 0.38 cmol<sup>c</sup> kg−1 (**Figure 3**). Organic matter has very high CEC. The significant increase in soil CEC observed in this study is likely due to the increase in SOM.

The estimated N release showed a highly significant increase over time (R<sup>2</sup> = 0.90), and the percentage increase was 1117%, with an annual rate of 5.6 kg ha−1 yr−1 compared to the year

**Figure 3.** Effect of using effluent water irrigation on cation exchange capacity. Different letters indicate significant differences using LSD (*P* < 0.05).

before using effluent water which was 4.6 kg ha−1 (**Figure 4**). Estimated N release is an estimate of N potentially released annually by decomposition of SOM. Estimated N release could be affected by many factors such as soil moisture, temperature, and soil type. This large increase was due to the fertilization and organic matter increase as well as substances added by effluent water because it often contains significant concentrations of organic nutrients, such as N and P [19]. Increases in this category were also a result of increased biomass production that translated to increases in SOM and eventually available N from organic matter decomposition.

Soluble S increased over time (R<sup>2</sup> = 0.82; **Figure 5**). The percentage increase during the 9 years of using effluent water was 413%. As mentioned earlier, this increase of S content over time was a result of using S burner to inject elemental S into irrigation water to reduce pH and bicarbonate concentration in effluent water [7]. Turf managers at Heritage Golf Course encountered a problem of increased black layer beneath putting green surfaces since 2003. Black layer is the formation of a layer of metal sulfide [20, 21], which forms when hydrogen sulfide (H<sup>2</sup> S) gas reacts with metal elements in the soil. Hydrogen sulfide gas is produced by sulfur-reducing bacteria (SRB). Black layer is typically associated with turfgrass chlorosis, wilting, thinning, and sometimes death.

Soluble S is the substrate for S reduction activity that leads to black layer. Therefore, the use of a S burner under effluent water irrigation might have partially contributed to the increased occurrence of black layer. Further research is needed to address the potential relationship between the incidence of black layer and effluent water irrigation.

Putting greens had low CEC (1.9 cmol<sup>c</sup>

CEC observed in this study is likely due to the increase in SOM.

0.38 cmol<sup>c</sup>

using LSD (*P* < 0.05).

82 Arid Environments and Sustainability

differences using LSD (*P* < 0.05).

kg−1) at the beginning of the experiment. This was

because it was mostly sand with low SOM and contained low inorganic colloids. Soil CEC is increased by 174% over the course of the experiment (R<sup>2</sup> = 0.86) and by an average rate of

**Figure 2.** Effect of using effluent water irrigation on soil organic matter. Different letters indicate significant differences

The estimated N release showed a highly significant increase over time (R<sup>2</sup> = 0.90), and the percentage increase was 1117%, with an annual rate of 5.6 kg ha−1 yr−1 compared to the year

**Figure 3.** Effect of using effluent water irrigation on cation exchange capacity. Different letters indicate significant

kg−1 (**Figure 3**). Organic matter has very high CEC. The significant increase in soil

In addition, extracted phosphates increased over time (R<sup>2</sup> = 0.83; **Figure 6**), and the percentage of increase during 9 years of using effluent water was 388%. This increase was expected because effluent water usually has more soil phosphates than freshwater. Increases in phosphates over years of using effluent water irrigation have been recorded in previous studies [9, 22].

**Figure 4.** Effect of using effluent irrigation on soil's estimated N release. Different letters indicate significant differences using LSD (P < 0.05).

done in 2005 found that effluent water provided enough K, Ca, and Mg for plants [24]. The authors suggested that soil with excessive amounts of K could lead to base saturation imbalance, and highly soluble salts tie up other elements such as B, Ca, and Mg. In contrast, higher amounts of Mg appeared to be a problem in clay soil, but it could help stabilize sandy soil. In this study, however, no clear pattern was found over time for potassium base saturation

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**Figure 7.** Effect of using effluent irrigation on soil exchangeable calcium. Different letters indicate significant differences

**Figure 8.** Effect of using effluent irrigation on soil exchangeable magnesium. Different letters indicate significant

percentage (**Figure 11**).

using LSD (*P* < 0.05).

differences using LSD (P < 0.05).

**Figure 5.** Effect of using effluent irrigation on soil soluble sulfur content. Different letters indicate significant differences using LSD (*P* < 0.05).

**Figure 6.** Effect of using effluent irrigation on soil phosphates. Different letters indicate significant differences using LSD (*P* < 0.05).

Similarly, exchangeable calcium (Ca), magnesium (Mg), potassium (K), and sodium (Na) significantly accumulated over time after using effluent water (**Figures 7**–**10**). The percentage of the increase after nine years of using effluent water was (Ca) 198%, (Mg) 116%, (K) 148%, and (Na) 452%. Exchangeable Na increased to 156 kg ha−1 after nine years of using effluent water. This increase could be due to the use of effluent water irrigation as some research has indicated. Soil Na concentration increased almost 5.5 times since the start of using effluent water, and the value (156 kg ha−1) was in the moderate risk range (>210 is in high risk) [23]. A study done in 2005 found that effluent water provided enough K, Ca, and Mg for plants [24]. The authors suggested that soil with excessive amounts of K could lead to base saturation imbalance, and highly soluble salts tie up other elements such as B, Ca, and Mg. In contrast, higher amounts of Mg appeared to be a problem in clay soil, but it could help stabilize sandy soil. In this study, however, no clear pattern was found over time for potassium base saturation percentage (**Figure 11**).

**Figure 7.** Effect of using effluent irrigation on soil exchangeable calcium. Different letters indicate significant differences using LSD (*P* < 0.05).

Similarly, exchangeable calcium (Ca), magnesium (Mg), potassium (K), and sodium (Na) significantly accumulated over time after using effluent water (**Figures 7**–**10**). The percentage of the increase after nine years of using effluent water was (Ca) 198%, (Mg) 116%, (K) 148%, and (Na) 452%. Exchangeable Na increased to 156 kg ha−1 after nine years of using effluent water. This increase could be due to the use of effluent water irrigation as some research has indicated. Soil Na concentration increased almost 5.5 times since the start of using effluent water, and the value (156 kg ha−1) was in the moderate risk range (>210 is in high risk) [23]. A study

**Figure 6.** Effect of using effluent irrigation on soil phosphates. Different letters indicate significant differences using LSD

**Figure 5.** Effect of using effluent irrigation on soil soluble sulfur content. Different letters indicate significant differences

using LSD (*P* < 0.05).

84 Arid Environments and Sustainability

(*P* < 0.05).

**Figure 8.** Effect of using effluent irrigation on soil exchangeable magnesium. Different letters indicate significant differences using LSD (P < 0.05).

**Figure 9.** Effect of using effluent irrigation on soil exchangeable potassium. Different letters indicate significant differences using LSD (*P* < 0.05).

In this study, a slight increase was recorded in the Ca base saturation percentage (R<sup>2</sup> = 0.35). In contrast, a reduction in Mg base saturation percentage was recorded (R<sup>2</sup> = 0.66) (**Figure 10**). Calcium and Mg affect each other's availability in the soil, and high Ca may tie up magnesium. However, the Ca/Mg ratios matched the balanced ratio at every sampling time (2.1–5.9) [25]. In general, the base saturation percentages for Ca, Mg, and K in this putting green are considered to be in the ideal or balanced ranges that many soil laboratories use to interpret soil test results. According to the basic cation saturation ratio theory, ideal plant growth will be achieved only when the soil's exchangeable Ca, Mg, and K concentrations are in range of

**Figure 11.** Effect of using effluent irrigation on soil base saturation Ca, Mg, K, and Na. Different letters indicate significant

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A significant increase over time was observed for extractable Fe (R<sup>2</sup> = 0.81). The percentage increase was 354% after 9 years of using effluent water, with an average rate of 25 mg kg−1 per year (**Figure 12**). These results were in agreement with a short-term (45 days) study done in Iran in 2011 [27]. The authors found that irrigation with wastewater significantly increased extractable Fe by 13% compared to the site that was irrigated with freshwater [27]. Although the effluent water for this course had low levels of Fe (0.3 mg L−1), the soil extractable Fe concentration significantly increased after using effluent water. After nine years of using effluent water, extractable Fe was 288 mg kg−1. Soil pH plays an essential role in micronutrient availability to plants. The availability of micronutrients such as Fe, Mn, and Zn in soil solution begins to decrease when soil pH is above 6.5. As soil pH increases, the availability of Fe decreases. As result, Fe deficiency is common in high pH soil. Iron is essential for chlorophyll synthesis and photosynthesis [28]. Effluent water could supply the soil with Fe with a proper soil pH range. In this site, Fe concentrations after nine years of using effluent water were in the ideal range (100–300 mg kg−1).

Likewise, extractable copper (Cu), manganese (Mn), and zinc (Zn) increased significantly over time (R<sup>2</sup> = 0.86, 0.87, and 0.89, respectively). The increased percentages after using effluent water were 290, 1220, and 1608%, by an average rate around 1.0, 3.2, and 2.1 mg kg−1 yr−1, respectively,

60–70% Ca, 10–20% Mg, and 4–6% K [26].

differences within the parameter using LSD (*P* < 0.05).

**Figure 10.** Effect of using effluent irrigation on soil exchangeable sodium. Different letters indicate significant differences using LSD (*P* < 0.05).

Increase in Na base saturation percentage was observed after nine years of effluent water irrigation at an average rate of 0.27% per year (**Figure 11**). Elevating exchangeable sodium percentage (ESP) observed over several years of effluent water irrigation can be of concern with regard to the preservation of water permeability and hydraulic conductivity on putting greens. ESP is a measurement of sodium hazard in soil, and ESP more than 15% can cause sodicity problems. Soil hydraulic conductivity decreases as ESP increases. However, sodicity depends on soil type. Soil with high clay content is affected more by ESP. Effluent water can cause Na build up over time in the soil. High concentrations of Na can affect the ability of water to move through the soil, that is, decrease infiltration.

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**Figure 11.** Effect of using effluent irrigation on soil base saturation Ca, Mg, K, and Na. Different letters indicate significant differences within the parameter using LSD (*P* < 0.05).

In this study, a slight increase was recorded in the Ca base saturation percentage (R<sup>2</sup> = 0.35). In contrast, a reduction in Mg base saturation percentage was recorded (R<sup>2</sup> = 0.66) (**Figure 10**). Calcium and Mg affect each other's availability in the soil, and high Ca may tie up magnesium. However, the Ca/Mg ratios matched the balanced ratio at every sampling time (2.1–5.9) [25]. In general, the base saturation percentages for Ca, Mg, and K in this putting green are considered to be in the ideal or balanced ranges that many soil laboratories use to interpret soil test results. According to the basic cation saturation ratio theory, ideal plant growth will be achieved only when the soil's exchangeable Ca, Mg, and K concentrations are in range of 60–70% Ca, 10–20% Mg, and 4–6% K [26].

A significant increase over time was observed for extractable Fe (R<sup>2</sup> = 0.81). The percentage increase was 354% after 9 years of using effluent water, with an average rate of 25 mg kg−1 per year (**Figure 12**). These results were in agreement with a short-term (45 days) study done in Iran in 2011 [27]. The authors found that irrigation with wastewater significantly increased extractable Fe by 13% compared to the site that was irrigated with freshwater [27]. Although the effluent water for this course had low levels of Fe (0.3 mg L−1), the soil extractable Fe concentration significantly increased after using effluent water. After nine years of using effluent water, extractable Fe was 288 mg kg−1. Soil pH plays an essential role in micronutrient availability to plants. The availability of micronutrients such as Fe, Mn, and Zn in soil solution begins to decrease when soil pH is above 6.5. As soil pH increases, the availability of Fe decreases. As result, Fe deficiency is common in high pH soil. Iron is essential for chlorophyll synthesis and photosynthesis [28]. Effluent water could supply the soil with Fe with a proper soil pH range. In this site, Fe concentrations after nine years of using effluent water were in the ideal range (100–300 mg kg−1).

Increase in Na base saturation percentage was observed after nine years of effluent water irrigation at an average rate of 0.27% per year (**Figure 11**). Elevating exchangeable sodium percentage (ESP) observed over several years of effluent water irrigation can be of concern with regard to the preservation of water permeability and hydraulic conductivity on putting greens. ESP is a measurement of sodium hazard in soil, and ESP more than 15% can cause sodicity problems. Soil hydraulic conductivity decreases as ESP increases. However, sodicity depends on soil type. Soil with high clay content is affected more by ESP. Effluent water can cause Na build up over time in the soil. High concentrations of Na can affect the ability of

**Figure 10.** Effect of using effluent irrigation on soil exchangeable sodium. Different letters indicate significant differences

**Figure 9.** Effect of using effluent irrigation on soil exchangeable potassium. Different letters indicate significant

water to move through the soil, that is, decrease infiltration.

using LSD (*P* < 0.05).

differences using LSD (*P* < 0.05).

86 Arid Environments and Sustainability

Likewise, extractable copper (Cu), manganese (Mn), and zinc (Zn) increased significantly over time (R<sup>2</sup> = 0.86, 0.87, and 0.89, respectively). The increased percentages after using effluent water were 290, 1220, and 1608%, by an average rate around 1.0, 3.2, and 2.1 mg kg−1 yr−1, respectively,

9 years of effluent water, Cu and Zn concentrations were very high in this putting green soil;

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Moreover, extractable aluminum (Al) increased over time after using effluent water (R<sup>2</sup> = 0.5) (**Figure 14**), and the percent increase was 63% up to 142 mg kg−1. These increases could be due to the effluent water use and could also be due to the soil aging and management practices. Toxic levels of Al are heavily dependent on the pH. In general, Al toxicity increases as soil acidity increases to a pH level of 4.8. In our study site, Al stayed bonded and not available to the plant.

A significant increase appeared in soil extractable boron (B) after the use of effluent water (R<sup>2</sup> = 0.68) (**Figure 15**), and the percent increase over time was 260% with an average rate of 0.06 mg kg−1 year−1. These results are most likely due to effluent water use and are in agreement with the previous study for the same golf course fairway soil. The extractable B gradually increased (R<sup>2</sup> = 0.56) after using effluent water in fairway soils [9]. The criteria for B concentration in soils are as follows: shoot growth of sensitive plants could decline as soil B exceeds 0.5–1.0 mg kg−1. Moderately sensitive plants would start to decline when soil B exceeds 1.0–2.0 mg kg−1. Kentucky bluegrass can tolerate soil B concentration of 2.0–4.0 mg kg−1, while tolerant grasses can tolerate soil B of 6–10 mg kg−1. The effluent water used in this study contained about 0.2 mg L−1 boron (**Table 1**). Soil samples collected had a range from 0.2 to 0.7 mg kg−1 of B. This average level of soil B concentration was higher in 2009 compared to what was measured in 1999 (0.2 mg kg−1), yet this range of B concentration was well below the toxic threshold for creeping bentgrass greens. The same study was done previously on Heritage Golf Course fairways [9]. In comparison between the greens and the fairways in these two studies, we found that both green and fairway soil chemistry changed over time after nine years of using effluent water. In many categories, results were similar for the greens and the fairways. In both studies, soluble S was increased significantly due to the S burner mentioned before. Increases in Na concentration, B concentration, soil ESP, and Na available for release were similar between the two studies. Although SOM increased in both studies, CEC increased in the green soil but not in the

**Figure 14.** Effect of using effluent irrigation on soil extractable aluminum. Different letters indicate significant differences

using LSD (*P* < 0.05).

however, toxicity is not a concern here for both elements due to the nonacidic soil pH.

**Figure 12.** Effect of using effluent irrigation on soil extractable iron. Different letters indicate significant differences using LSD (*P* < 0.05).

for Cu, Mn, and Zn, respectively (**Figure 13**). This finding is in disagreement with the previous study for fairways on the same golf course which suggested that no pattern of change was recorded for extractable Cu, Mn, and Zn after using 9 years of effluent water [9]. These micronutrient availabilities are similar to the availability of Fe and depend on pH as well. Sandy soil usually has low concentrations of micronutrients such as Fe, Mn, Cu, and Zn [29]. Copper is an enzyme activator and disease fighter, and the Cu minimum value needed in the soil is 1.5 mg kg−1, and a value higher than 4 mg kg−1 is excessive [30]. Copper and Zn affect each other availabilities to plants, and ideally soil Cu concentration should be half of Zn. Our results showed that after

**Figure 13.** Effect of using effluent irrigation on soil extractable manganese, copper, and zinc. Different letters indicate significant differences within the parameter using LSD (*P* < 0.05).

9 years of effluent water, Cu and Zn concentrations were very high in this putting green soil; however, toxicity is not a concern here for both elements due to the nonacidic soil pH.

Moreover, extractable aluminum (Al) increased over time after using effluent water (R<sup>2</sup> = 0.5) (**Figure 14**), and the percent increase was 63% up to 142 mg kg−1. These increases could be due to the effluent water use and could also be due to the soil aging and management practices. Toxic levels of Al are heavily dependent on the pH. In general, Al toxicity increases as soil acidity increases to a pH level of 4.8. In our study site, Al stayed bonded and not available to the plant.

A significant increase appeared in soil extractable boron (B) after the use of effluent water (R<sup>2</sup> = 0.68) (**Figure 15**), and the percent increase over time was 260% with an average rate of 0.06 mg kg−1 year−1. These results are most likely due to effluent water use and are in agreement with the previous study for the same golf course fairway soil. The extractable B gradually increased (R<sup>2</sup> = 0.56) after using effluent water in fairway soils [9]. The criteria for B concentration in soils are as follows: shoot growth of sensitive plants could decline as soil B exceeds 0.5–1.0 mg kg−1. Moderately sensitive plants would start to decline when soil B exceeds 1.0–2.0 mg kg−1. Kentucky bluegrass can tolerate soil B concentration of 2.0–4.0 mg kg−1, while tolerant grasses can tolerate soil B of 6–10 mg kg−1. The effluent water used in this study contained about 0.2 mg L−1 boron (**Table 1**). Soil samples collected had a range from 0.2 to 0.7 mg kg−1 of B. This average level of soil B concentration was higher in 2009 compared to what was measured in 1999 (0.2 mg kg−1), yet this range of B concentration was well below the toxic threshold for creeping bentgrass greens.

for Cu, Mn, and Zn, respectively (**Figure 13**). This finding is in disagreement with the previous study for fairways on the same golf course which suggested that no pattern of change was recorded for extractable Cu, Mn, and Zn after using 9 years of effluent water [9]. These micronutrient availabilities are similar to the availability of Fe and depend on pH as well. Sandy soil usually has low concentrations of micronutrients such as Fe, Mn, Cu, and Zn [29]. Copper is an enzyme activator and disease fighter, and the Cu minimum value needed in the soil is 1.5 mg kg−1, and a value higher than 4 mg kg−1 is excessive [30]. Copper and Zn affect each other availabilities to plants, and ideally soil Cu concentration should be half of Zn. Our results showed that after

**Figure 12.** Effect of using effluent irrigation on soil extractable iron. Different letters indicate significant differences using

**Figure 13.** Effect of using effluent irrigation on soil extractable manganese, copper, and zinc. Different letters indicate

significant differences within the parameter using LSD (*P* < 0.05).

LSD (*P* < 0.05).

88 Arid Environments and Sustainability

The same study was done previously on Heritage Golf Course fairways [9]. In comparison between the greens and the fairways in these two studies, we found that both green and fairway soil chemistry changed over time after nine years of using effluent water. In many categories, results were similar for the greens and the fairways. In both studies, soluble S was increased significantly due to the S burner mentioned before. Increases in Na concentration, B concentration, soil ESP, and Na available for release were similar between the two studies. Although SOM increased in both studies, CEC increased in the green soil but not in the

**Figure 14.** Effect of using effluent irrigation on soil extractable aluminum. Different letters indicate significant differences using LSD (*P* < 0.05).

**Author details**

Fort Collins, USA

NGF; 2000

98-108

**References**

Hanan Isweiri and Yaling Qian\*

\*Address all correspondence to: yaling.qian@colostate.edu

Department of Horticulture and Landscape Architecture, Colorado State University,

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**Figure 15.** Effect of using effluent irrigation on soil extractable boron. Different letters indicate significant differences using LSD (*P* < 0.05).

fairway. In contrast, some soil parameters responded differently in the two studies. For example, significant increases in trace elements such as Cu, Zn, Mn, and Al were only observed in the green studies but not in fairways. Similarly, Fe concentration significantly increased in the greens but not in the fairways. These differences between the two studies could be due to the different soil type and structure in the greens and the fairways. Further studies are needed to determine if the change of soil parameters would continue over time.
