Improving fertilizer guidelines for increased efficiency and environmental stewardship.

Transcription

1 Improving fertilizer guidelines for increased efficiency and environmental stewardship. Bruce Linquist, David Spencer, Luis Espino, Chris Greer, Jim Hill, Randal Mutters, Mark Lundy, Cameron Pittelkow, Arlene Adviento Borbe, and Chris van Kessel 2011 Annual Winter meetings Richvale, Glenn, Williams, Yuba City

2 Outline Brief background Nitrate leaching Greenhouse gas emissions P management in California rice systems

3 Quantify N losses due to NO 3 leaching in Background California rice systems Nitrate posses a health concern in ground water Levels above 10 ppm NO 3 N in considered a health risk by the EPA Agriculture can be a major contributor to nitrate in ground water

4 Procedure Identified 8 rice fields that included representative sites as well as extreme sites Took soil cores to a depth of 2m (7 ft) Measurements across depth of soil core NO 3 N Soil texture Dissolved organic carbon Denitrification of surface soil Hydraulic conductivity of soil below root zone

5 Glenn Butte Butte Yuba Yuba Colusa Colusa Sutter Sutter Yolo Placer Placer Yolo Sacramento Sacramento

6 Soil nitrate at different soil depths 5 Tibbitts Corancho Soil nitrate N (ppm) Mayben Meyers Mathews Brenan Stutz McLelan Soil depth (cm)

7 Why soil nitrate levels are low in rice systems Soil nitrate levels are low in the surface soil to begin with (0.4 to 4.2 ppm) Winter weeds take up nitrate Straw immobilizes Growers do not apply NO 3 fertilizer Soils remain flooded for much of the season preventing nitrification (NH 4 to NO 3 ) Denitrification rates are very high (NO 3 to N gas) Downward water percolation is very slow

8 Quantifying N 2 O and CH 4 emissions in California rice systems and possible mitigation strategies

9 Global GHG emissions Rice is the largest contributor to agricultural CH 4 emissions (Upper estimates: 15 20% of global CH 4 ). Agriculture is the largest contributor to N 2 O emissions (>60%) CH 4 : 25 X more potent than CO 2 N 2 O: 298 X more potent IPCC (2007) than CO 2 UC DAVIS University of California

10 Methane emissions from rice systems Methane emissions driven by water and organic matter management UC DAVIS University of California

11 Nitrous oxide emissions from rice systems N 2 O NH 4 + NO 3 - N 2 O N 2 Nitrification Aerobic/drain Denitrification Flooding UC DAVIS University of California

12 Factors affecting GHG emissions Practice CH 4 N 2 O Soil submergence + - Intermittent vs. cont. flood - + Straw addition + - Low C:N material addition (i.e. green manures) + + Urea vs. no N ± + AS vs. no N or urea - + Sulfate -? Incorporate N vs. broadcast - - Nitrification/urease inhibitors - - No till vs. conventional till - + Presence of plants + + Variety effects ± ± High yield vs. low yield +? Clay vs. sandy soil - - Linquist, 2010 Unpublished report UC DAVIS University of California

13 Phosphorus management in California rice systems.

14 Phosphorus management in California rice systems. Dollar/ton Fertilizer costs: Source: USDA Nitrogen solutions (30%) Urea 44 46% nitrogen Sulfate of ammonium Super phosphate 44 46% phosphate Potassium chloride 60% potassium

15 Phosphorus management in California rice systems. Frequency of P deficiencies Less than 10% of CA rice soils respond significantly to added P fertilizer. Determining the P status of your soil. Soil test Plant tissue test Input output P budget How much do should you apply? When should you apply? P management and algae

16 Determining the P status of your soil Soil test Olsen P test (sodium bicarbonate) above 6 9 ppm 20% of the soils with Olsen P less than 9 ppm had significant yield responses to applied P fertilizer Bray test not good for CA rice soils Plant tissue test Y leaf tissue test. P concentration at 35 DAS 0.2% P 60% of sites with Y leaf of 0.2% or less had significant yield responses to applied P fertilizer Input output P budget

17 P management effects on soil P 35 y = x R² = Olsen P (ppm) Annual P budget (lb P2O5/yr)

18 Determining the P status of your soil Soil test Olsen P test (sodium bicarbonate) above 6 9 ppm 20% of the soils with Olsen P less than 9 ppm had significant yield responses to applied P fertilizer Bray test not good for CA rice soils Plant tissue test Y leaf tissue test. P concentration at 35 DAS 0.2% P 60% of sites with Y leaf of 0.2% or less had significant yield responses to applied P fertilizer Input output P budget

19 Determining the P status of your soil Soil test Olsen P test (sodium bicarbonate) above 6 9 ppm 20% of the soils with Olsen P less than 9 ppm had significant yield responses to applied P fertilizer Bray test not good for CA rice soils Plant tissue test Y leaf tissue test. P concentration at 35 DAS 0.2% P 60% of sites with Y leaf of 0.2% or less had significant yield responses to applied P fertilizer Input output P budget

20 Input output P budget: Think of soil as a phosphorus bank When managed correctly P fertilizer is relatively immobile in soils. No gas losses Little is lost through water Little lost by leaching Inputs Fertilizer Outputs Grain removal (0.23% P / 0.52% P 2 O 5 ) Straw removal (0.08% P / 0.18% P 2 O 5 )

21 Input output P budget Develop a budget Inputs (lb/ac of P2O5 as fertilizer) Outputs (lb/ac removed in grain and straw) Develop such a budget over at least a 5 yr period take average In our study the only sites with significant yield responses had negative P budgets

22 P budget effects on soil P and yield response 35 y = x R² = Olsen P (ppm) Annual P budget (lb P2O5/yr)

23 Input output P budget Calculate your own budget Develop a budget Inputs (lb/ac of P2O5 as fertilizer) Outputs (lb/ac removed in grain and straw) Develop such a budget over at least a 5 yr period take average

24 Grain yield Only grain removed P fertilizer added (lb P 2 O 5 /ac) P balance (lb P 2 O 5 /ac)

25 Grain yield Remove grain and ½ of straw P fertilizer added (lb P 2 O 5 /ac) P balance (lb P 2 O 5 /ac)

26 How much P fertilizer should you apply? Soils have very high P levels based on soil test (i.e. above 20 ppm) and positive P budget Apply no P Soils have very low P (less than 6) and a negative P budget Build up soil P In most cases where P is not limiting use a maintenance strategy Apply what is removed by the crop How much is removed? Olsen P (ppm) y = x R² = Annual P budget (lb P2O5/yr)

27 Grain yield Only grain removed P fertilizer added (lb P 2 O 5 /ac) P balance (lb P 2 O 5 /ac)

28 Maintenance applications based on crop removal P removed (lb P 2 O 5 /ac) Grain Grain + 1/2 straw Grain yield (cwt)

29 Phosphorus management in California rice systems. Frequency of P deficiencies Less than 10% of CA rice soils respond significantly to added P fertilizer. Determining the P status of your soil. Soil test Plant tissue test Input output P budget How much do should you apply? When should you apply? P management and algae

30 Procedures Two locations Butte county Both had low soil P levels P treatments in rings 0, 14, 28, and 42 DAS Measurements Soil extractable P Y leaf P concentrations (35 DAS) Water P concentrations: 2X/week from P application to 3 wk after Yield (only available for 1 site at this time) Algae

31 Soil P status and algae Dry Weight Per Square Meter (G) kg P ha at Flooding MYERS 7 Days After Treatment Site M Dry Weight Per Square Meter (G) kg P ha at Flooding RYSTR 7 Days After Treatment Site R 0 N Y N Y N Y + P 0 N Y N Y N Y + P 05/13 05/27 06/10 Date 05/26 06/09 06/23 Date

32 Grain yield response to delayed P applications b a a a a c ab ab a b Grain yield 14%) Site M Grain yield Site R 0 0 No P P at planting P 14 DAS P 28 DAS P 42 DAS No P P at planting P day 14 P day 28 P day 42

33 Delayed P application effects on water quality No P M May 12 May 22 May 1 Jun 11 Jun 21 Jun 1 Jul 11 Jul No P R May 1 Jun 11 Jun 21 Jun 1 Jul 11 Jul 21 Jul 0.050

34 Summary of P management In P limited fields such as those used in this study Spring applications and applications up to 28 DAS give similar yields If Fall applications are made, a higher P rate may be needed For P sufficient fields (maintenance P application) 90 95% of CA rice fields P applications can be made in the Fall, early spring or after planting. Delaying P applications reduces algae growth. P applications should be made at least 2 weeks before the onset maintenance flow (or other drainage event) to avoid potential water quality problems. When applying P use a P source that has the lowest amount of N possible (i.e ). If this P is applied during the season (at planting or delayed) reduce the amount of N being applied from the total N rate you want to apply.

35 THANK YOU Special thanks to all cooperating farmers and the California Rice Research Board for supporting this research