Nutrients in Runoff from a Furrow‐Irrigated Field after Incorporating Inorganic Fertilizer or Manure

Abstract

Use of dairy manure to supply crop nutrients is gaining broader acceptance as the cost of fertilizer rises. However, there are concerns regarding manure's effect on water quality. In 2003 and 2004, we measured sediment, NO3–N, NH4–N, K, dissolved reactive P (DRP), and total P (TP) concentrations in runoff from furrow irrigated field plots (6–7 irrigations yr−1) cropped to corn (Zea mays L.) in the semiarid climate of southern Idaho. Annual treatments included 13 (Year 1) and 34 Mg ha−1 (Year 2) stockpiled dairy manure (M); 78 (Year 1) and 195 kg N ha−1 (Year 2) inorganic N fertilizer (F); or control–no amendment (C). Available N in manure applied each year was similar to amounts applied in fertilizer. Constituent concentrations (mg L−1) in runoff ranged widely among all treatments: sediment, 10 to 50,000; NO3–N, 0 to 4.07; NH4–N, 0 to 2.28; K, 3.6 to 46.4; DRP, 0.02 to 14.3; and TP, 0.03 to 41.5. Over both years, fertilizer and manure treatments increased irrigation mean values (averaged across irrigations) for NO3–N runoff concentrations (M = 0.30, F = 0.26, C = 0.21 mg L−1) and mass losses (M = 0.50, F = 0.42, C = 0.33 kg ha−1) relative to the control. Over both years, the manure treatment also increased mean irrigation runoff concentrations of DRP (M = 0.19, F = 0.09, C = 0.08 mg L−1) and K (M = 1.13, F = 0.79, C = 0.62 mg L−1) compared with fertilizer and control plots. Average DRP and K runoff mass losses were 2.0 to 2.4 times greater in manure treatments than in control plots. Neither F or M affected season‐long cumulative infiltration. Runoff DRP and inorganic‐N losses appeared to be influenced more by the timing of the amendment application and environmental conditions than by the quantity of nutrients applied. Nutrient additions to furrow irrigated soils, whether from fertilizer or manure, can potentially increase nutrient losses in irrigation runoff, with the degree of impact depending on the nutrient, amount, and timing of application and whether inorganic fertilizer or manure was applied.

Managing Runoff Water Quality from Recently Manured, Furrow‐Irrigated Fields

“…1, six runoff water quality samples per irrigation were collected at 5 min and 0.5, 2, 8, 14, and 24 h aft er furrow advance. Th ese data verifi ed the results from other studies (Lentz and Lehrsch, 2010) showing that the greatest changes in constituent concentrations occurred in the fi rst 4 to 5 h aft er runoff began, with only minor changes occurring thereaft er. Furthermore, the 0.5-h sample time was not as defi nitive as a 1-h sampling time because runoff rates early in the runoff period were relatively small.…”

“…Dissolved reactive P concentrations in runoff are less correlated with sediment, and irrigation mean values range from 0.04 to 0.18 mg L −1 (Fitzsimmons et al, 1972;Westermann et al, 2001;Bjorneberg et al, 2006;Lentz and Lehrsch, 2010). Runoff DRP was found to be infl uenced by furrow length, the residence time of water in the furrow (stream velocity), the quantity of crop residue exposed in the furrow (Bjorneberg and Aase, 2004;Westermann et al, 2001), and infi ltration fraction (Lentz and Lehrsch, 2010). Fitzsimmons et al (1972) reported mean N concentrations in a random sampling of surface irrigation infl ow and runoff waters from 30 farms in southwest Idaho.…”

“…Nutrient additions to the soil, whether from animal wastes or inorganic fertilizers, generally increase nutrient runoff losses in irrigation return fl ows; however, the quantity lost varies depending on the type of amendment, nutrient, and timing of application (Lentz and Lehrsch, 2010). When amendments were incorporated into soil, Lentz and Lehrsch (2010) concluded that runoff losses of soil DRP and inorganic N were substantially infl uenced by biocycling processes, which in turn were infl uenced by application timing and environmental conditions.…”

“…When amendments were incorporated into soil, Lentz and Lehrsch (2010) concluded that runoff losses of soil DRP and inorganic N were substantially infl uenced by biocycling processes, which in turn were infl uenced by application timing and environmental conditions. Under rainfed conditions, tillage following P application can decrease runoff DRP losses by reducing the contact between the applied nutrient and surface waters, but increase TP losses by increasing sediment in the runoff (Bundy et al, 2001;Kimmell et al, 2001).…”

“…In a 2-yr study, Lentz and Lehrsch (2010) monitored runoff from fall-applied vs. springapplied manure; however, manure rates between the two applications were dissimilar. Management eff ects on runoff water quality from manure-amended fi elds are well documented for rainfall events (Zhao et al, 2001;Andraski et al, 2003;Little et al, 2005;Smith et al, 2007;Soupir et al, 2006;Gilley et al, 2007;Kaiser et al, 2009).…”