MANAGEMENT AND CONSERVATION PRACTICES TO IMPROVE WATER QUALITY IN AGROECOSYSTEMS OF THE NORTHEASTERN US
Location: Pasture Systems & Watershed Management Research
Title: Ammonia volatilization, corn and forage yield as a function of poultry litter application methods
Submitted to: Meeting Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: October 1, 2012
Publication Date: N/A
Interpretive Summary: An interpretive summary is not required.
Manure management has emerged as a significant agronomic and environmental concern in Brazil. Most manure is broadcast to the soil surface where it remains vulnerable to environmental processes that significantly lower the manure’s nitrogen fertilizer value and negatively impact air quality. In general, incorporation of manure into the soil has proven to be an effective technique to decrease ammonia emissions. Because most land in Brazil is in no-till management, options are needed to incorporate manure that do not rely upon tillage. While low-disturbance injection systems have long been available for liquid manure, only recently have similar systems been developed for dry manure. In the U.S., several generations of dry manure applicators have been developed by the US Department of Agriculture (USDA) with the purpose of applying poultry litter into row crop and grassland soils with the minimal disturbance. Through a collaborative research project between the Federal University of Maranhão (Brazil) and the USDA we sought to evaluate the potential for using subsurface application technology in Brazil. Subsurface poultry litter application was compared with surface application of litter and tillage incorporation of litter. We report the effects of this subsurface application of poultry litter on ammonia (NH**3) volatilization, crop and forage yields.
Materials and methods
Two experiments were conducted in different locations of Brazil. One experiment was established in November, 2009 in the city of Rio Verde, state of Goiás, located in the Center-west region of Brazil (Experimental Area 1); and the second experiment was established in March, 2010 in the city of Chapadinha, state of Maranhão, located in the Northeast region of Brazil (Experimental Area 2). Four treatments were evaluated in both experiments: (1) control-without poultry litter application, (2) surface application, (3) incorporated with tillage and (4) subsurface applied. In Experimental Area 1, hybrid corn (Zea mays L.) AG8021 was planted twenty days after poultry litter application. In Experimental area 2, the perennial grass Brachiaria brizantha cv. Piatã was established three days after poultry litter application. Volatilized NH**3 was captured by a semi-opened free static chamber as described and calibrated by Araújo et al. (2009). The chambers were installed in each plot just after poultry litter application, and samples were collected by replacing the foam sorption 24, 48, 144, 196 and 296 hours after poultry litter application for both site areas. Analysis of variance (ANOVA), Tukey’s mean separation and Student’s t-test were performed in Minitab v. 15 (Minitab Inc., 2001) for all data obtained.
Results and discussion
Experimental Area 1: Rio Verde, Goiás - Brazil : At the time of poultry litter application the soil was moist due to 55 mm rainfall three days before litter application, and the temperature ranged between 26 and 28 deg C (Figure 1). For the first 24 hours N-NH**3 emissions were not significant, and the average emission across all treatments was 1.6 kg N-NH**3 ha**-1. According to Hargrove (1998), 10 to 20 mm of precipitation is enough to minimize ammonia emissions for most of soils. This effect is due to the lower gas diffusion in moist soil. In the following days there was no additional rainfall, and air temperature increased to 34 deg C. The greatest NH**3 losses (97 and 124 Kg N-NH**3 respectively) were observed at 48 and 144 hrs after litter application. During this period, as the temperature increased, the drying soil increased the potential for NH**3 emissions
After 144 hours of poultry litter application, Twenty-nine mm rainfall fell 144 hrs after litter application, at which point the temperature decreased to 19 deg C. This weather change corresponded with a decrease in ammonia emission rates to 31 kg N- NH**3 ha**-1. Cooler, wetter weather persisted over the following days, with 53 mm cumulative rainfall and an average temperature of 23 deg C. By 288 hrs after poultry litter application, NH**3 emissions had decreased to 5.8 kg N- NH**3 ha**-1. No significant decrease in N- NH**3 emissions was observed between the subsurface applied and surface applied litter treatments. However, N- NH**3 emissions following incorporation with tillage were significantly lower than emissions from the other litter application treatments and were not significantly different than the unamended control. Results point to the need for better closure of the furrows into which litter is subsurface applied in order to reduce NH**3 with subsurface litter placement.
Although the N- NH**3 emissions were greatest from the surface and subsurface application treatments, these treatments also had the highest corn yields (P less than0.05), with respective increases of 12 and 20% above the control. In the US, research suggests that moisture conservation around subsurface applied litter and micronutrients in litter may contribute to yield benefits that are not explained by nitrogen use efficiency.
Experimental Area 2: Chapadinha, Maranhão – Brazil: At the Experimental Area 2, there were two rainfall events totaling 36 mm four days before litter application, and for the first 24 hours the cumulative NH**3 loss averaged 0.85 kg N- NH**3 ha**-1across all treatments (Figure 2). During the period of 48, 144, 192 and 288 hrs after poultry litter application no rainfall occurred, and NH**3 emissions were greatest during this period. At the end of 480 hours the temperature and precipitation were constant, and N- NH**3 emissions decreased to an average of 18 kg N- NH**3 ha**-1.
As with Experimental Area 1, surface application represented greater (P less than 0.05) N- NH**3 losses (138 kg N- NH**3 ha**-1), which was 84% higher when compared with the control. When poultry litter was incorporated and injected, NH**3 emissions decreased in 38% and 63% compared with surface application. Several authors reported that manure incorporation reduces nitrogen losses through volatilization by 70% compared with surface application (Huijsmans et al., 1997; Frost 1994; Missselbrook & Pain, 1997).
In general, forage yields were greatest (P less than 0.05) with subsurface application and tillage incorporation of poultry litter. Differences persisted across the four cuttings, resulting in a cumulative forage yield difference of 1.8 kg DM ha**-1 between the subsurface application treatment and the control, and a difference of 0.6 kg DM ha**-1 between the subsurface application treatment and the conventional (surface) application treatment. While both subsurface application and tillage incorporation treatments demonstrated significant benefits to forage production in the first year after establishment, only subsurface litter application can be considered viable for repeated litter application to perennial grasses in subsequent years.
Simulation of subsurface litter application revealed significant yield benefits in corn and grass forage production systems. However, we did not observe similar benefits with subsurface litter application and NH**3. It may be that poor closure of furrows into which litter was placed contributed to the great than expected NH**3 emissions. Better furrow closure can be expected with mechanical applicators, such as the USDA Subsurfer.