Nitrous oxide emissions, N uptake, biomass, and rubber yield in N-fertilized, surface-irrigated guayule

Authors: Bronson, Kevin; Hunsaker, Douglas - Doug; EL-SHIKHA, D.M. - University Of Arizona; Rockholt, Sharette; Williams, Clinton; RASUTIS, D. - Nutrition Therapy Institute; SORATAN, K. - Naresuan University; Venterea, Rodney - Rod

Submitted to: Industrial Crops and Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/21/2021
Publication Date: 4/30/2021
Citation: Bronson, K.F., Hunsaker, D.J., El-Shikha, D., Rockholt, S.M., Williams, C.F., Rasutis, D., Soratan, K., Venterea, R.T. 2021. Nitrous oxide emissions, N uptake, biomass, and rubber yield in N-fertilized, surface-irrigated guayule. Industrial Crops and Products. 167. Article 113561. https://doi.org/10.1016/j.indcrop.2021.113561.
DOI: https://doi.org/10.1016/j.indcrop.2021.113561

Interpretive Summary: Nitrous oxide (N2O) emissions from nitrogen (N) fertilizer applied to row crops makes up a large portion of the greenhouse gas loading from agricuture to the atmosphere. Guayule is a desert perennial shrub being promoted for Central Arizona farmers for the first time since the 1940s as a source of natural rubber. atex. However, N2O emissions and N uptake have not been previously quantified in this multi-year cropping system. We conducted a 23-month study on transplanted and irrigated guayule on a Casa Grande sandy loam in Maricopa, AZ to assess the agronomic and environmental responses to nitrogen (N) fertilizer application rate. Four N fertilizer rates ranging from 0 to 252 kg N ha-1 were applied as ammonium sulfate in three splits. Nitrous oxide emissions were measured with 1-L vented chambers 34 times from over 98 weeks from 17 April 2013 to 6 March 2015 with pauses during winter dormant seasons. Nitrogen rate significantly affected N2O emissions, which ranged from 2.0 to 5.5 kg N ha-1 for the 0 and 252 kg N ha-1 fertilizer rates. The percentage of added ammonium sulfate-N emitted as N2O ranged from 0. 7 to 1.4 %, which are in the range of those for other better-studied crops such as corn and cotton. Nitrogen uptake by guayule averaged 191 kg N ha-1 for biomass and rubber yields of 19 Mg ha-1 and 1070 kg ha-1, respectively There was no effect of N rate on N uptake, biomass, or rubber yields because of high initial soil profile nitrate (NO3) levels. A N balance of inputs (initial soil NO3, N fertilizer, NO3-N added in irrigation) and outputs (N uptake, N2O, and N2 emissions) was constructed. Unaccounted for N was apparently lost as NO3 leaching below the root zone. The N uptake levels reported here can be used in updated, improved N fertilizer recommendations for guayule. Additional N fertilizer rate studies on guayule rubber yield are needed.

Technical Abstract: Nitrous oxide (N2O) emissions from N fertilizer applied to row crops makes up a large portion of the greenhouse gas loading to the atmosphere. Guayule (Parthenium argentatum A. Gray) is a desert perennial shrub being promoted for Central Arizona farmers as a source of natural rubber and hypoallergenic latex. Emissions of the greenhouse gas N2O and crop N uptake have not been previously quantified in this multi-year cropping system. A 2.5-year study was conducted on transplanted and surface-irrigated guayule on a Casa Grande sandy loam in Maricopa, AZ to assess the agronomic and environmental responses to N fertilizer application rate. Four N fertilizer rates ranging from 0 to 252 kg N ha-1 were applied as ammonium sulfate in three splits. Nitrous oxide emissions were measured with 1-L vented chambers 34 times over 98 weeks from 17 April 2013 to 6 March 2015 with pauses during winter dormant seasons. Nitrogen rate significantly affected N2O emissions, which ranged from 1.2 to 4.5 kg N ha-1 for the 0 and 252 kg N ha-1 fertilizer rates. Emission factors were 1.5, 1.4, and 1.3% of the added ammonium sulfate-N emitted as N2O for 84, 168, and 250 kg N ha-1, respectively, which are in the range of those for other better-studied crops such as corn (Zea mays L.) and cotton (Gossypium hirsutum L.) Nitrogen uptake by guayule averaged 191 kg N ha-1 for biomass and rubber yields of 19 Mg ha-1 and 1070 kg ha-1, respectively. There was no effect of N rate on N uptake, biomass, or rubber yields because of initial soil profile nitrate (NO3) levels of 85 to 150 kg NO3-N ha-1. A N balance of inputs (initial soil NO3, N fertilizer, NO3-N added in irrigation) and outputs (N uptake, N2O, and dinitrogen (N2) emissions) was constructed. Unaccounted-for N was apparently lost as NO3 leaching below the root zone. In conclusion, the informative N2O emissions data presented are the first for guayule, and the N uptake levels reported here can be used in updated, improved N fertilizer recommendations for guayule.