Effect of Agricultural on Nitrate Leaching in the Judith River Watershed

Clain Jones, Andrew John, Adam Sigler, Perry Miller and Stephanie EwingDepartment of Land Resources and Environmental SciencesEffect of Agricultural Practices on Nitrate Leaching in the Judith River Watershed

Project Sub-ObjectivesEvaluate the effects of alternative agricultural management practices on:

1.Nitrate Leaching 2.Net Revenue

Under net revenue, discuss what you will be analyzing (yield and protein)2Nitrate leaching in Montana agroecosystems: Concept and timingHighest precipitation period: Late Apr to Mid-JuneHighest nitrate levels in soil: after fallow and after fertilization (often Apr in Judith Basin)How do those periods compare with crop N uptake?

Fallow

Top-dress amount and timing based on wheat growth stage to not hurt yield

Nutrient Uptake Timing (EB0191)http://landresources.montana.edu/soilfertility/publications.htmlSaskatchewanAdapted from Malhi et al. 2006Apr May June JulyAugDeep Soil Water Collected

Adam5Practices that can decrease nitrate leaching in agro-ecosystemsSeed perennial and/or deep rooted annual cropsSprinkle vs flood irrigationSoil sample for nitrate to determine N fertilizer rateSelect reasonable yield goalCredit N from manure and legumesFertilize in spring rather than fallUse a slow release fertilizerSplit applicationGrow legumes (dont need to fertilize with N)Recrop (crop every year) rather than summer fallow

Study Design: Management PracticesGrower Standard Practice (GSP)Wheat-barley-fallow rotationNitrogen fertilizer: surface broadcast, early spring Alternative Management Practices (AMP) vs GSPPea vs FallowSplit fertilizer application vs single early spring broadcast Controlled release urea (CRU) with seed vs early spring broadcastAlternative management practices were selected by our two research advisory groups based on how adoptable the practices wereTalk about the pros and cons for GSP- Fallow recharges soil moisture but no biomass uptake means NO3- is more available to be leachedBroadcast Application- Nitrogen is applied all at once meaning that if plants do not take up soon enough, rainfall event could move it down and out of the rootzone.

7Study Design: FieldsComparisons of AMP vs GSP treatments were made for two years (2013, 2014) on two fields each. Fields located near Stanford (Field A), Moccasin (Field B), and Moore (Field C)

Field AField BStudy Design: Field Layout and Sampling Locations

2014 Winter Wheat

GSP AMP

201220132014CRUGSPSplit AppFallowCRUGSPSplit AppStudy Design: Field C (near Moore)10Calculating Leaching by Nitrogen Mass Balance

Leached Nitrate = Inputs outputs + initial soil nitrate final soil nitrateDiscuss some of the variables that have been collected through the study.11Nitrogen Mass BalanceLeached Nitrate = Fertilizer N + N fixed + Net N mineralized denitrification crop N uptake N volatilized + initial soil nitrate final soil nitrateFertilizer N: from Judith collaboratorsN-fixed: natural abundance methodNet N mineralized denitrification: soil nitrate differences when no leaching based on precipitation and soil moisture (e.g. 2012 to mid-May 2013). Modelled during other periods. Crop N uptake biomass samplingN volatilized Rick Engels results from Fergus County

Biggest unknowns in the budget are N mineralization and denitrificationExplain what extrapolation means and why we decided to use it12Status of leaching estimate Still developing mineralization model Can calculate available N recovery for 2013 winter wheat. Available N Recovery (%) = ((N in grain and straw)/(soil nitrate in Aug 2012 + fertilizer N))*100Differences between treatments could suggest differences in leachingAvailable Nitrogen Recovery in 2013 winter wheat* - Significant difference (P