Bruce Linquist UC Davis, Dept. Plant Sciences University of California Coopera;ve Extension July 24, 2015 Fertility and Crop Nutrition
Bruce Linquist UC Davis, Dept. Plant Sciences
University of California Coopera;ve Extension July 24, 2015
Fertility and Crop Nutrition
UC DAVIS University of California
Outline • Why is nutrient management important? • Rice soils • Approaches to nutrient management • N, P, and K
– Func=on and deficiency – Nutrient in the soil – 4R management – Effect of straw management
• Adjus=ng nutrient management for different systems – Drill-‐seeding – Stale seedbed
UC DAVIS University of California
Why is nutrient management important?
• Economics – Cost – Yields
• Pollu=on – Ground and surface waters – Air quality
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1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2015
Dollars per to
n of fe
r;lizer
Fer;lizer prices 1960-‐2013 (USDA)
Nitrogen solu=ons (30%)
Urea 44-‐46% nitrogen
Super-‐phosphate 44-‐46% phosphate
Potassium chloride 60% potassium
UC DAVIS University of California
Flooded rice soils in California • Aerobic and anaerobic soils
– The amount of oxygen in soils affects: • Soil microbiology • Soil pH • Nutrient transforma=ons
• Heavy clay soils that are rela=vely impermeable – High reten=on of nutrients – Limited leaching – A lot of potassium
UC DAVIS University of California
Approaches to nutrient management
• The goal – match nutrient supply with crop requirements – minimize nutrient losses from fields.
• Properly managed fer=lizers – support cropping systems that provide economic, social and environmental benefits.
• Poorly managed nutrient applica=ons can – decrease profitability and increase nutrient losses, poten=ally degrading water and air quality.
UC DAVIS University of California
Amount of nutrient in plant at harvest (lb/1000 lb grain yield)
15.6
2.7
15.1
1.6
3.6 3.1
0.45 0.45 0.04 0.01 0.01
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N P K S Ca Mg Fe Mn Zn Cu B
Nutrie
nt in plant at ;
me of harvest
Nutrient
Nutrient uptake and root growth
Plan;ng
What is this material? 0.7 0.3 1.7
Nutrients (lb) in 1 ton (2000 lb) of rice straw
• N 14 lb • P 6 lb • K 28 lb
• Value (2012 fer;lizer prices)
• $31.34
UC DAVIS University of California
Straw management and how it affects nutrient management
• Removing straw will increases nutrient requirement of all major nutrients-‐especially K
• Important to incorporate/roll straw to facilitate decomposi=on during winter
• Can reduce N inputs by 25 lb/ac. IF straw is incorporated
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UC DAVIS University of California
Maximizing nutrient use efficiency through 4R management
• The 4 Rs – Right rate – Right source – Right place – Right =me
UC DAVIS University of California
Nitrogen
• Applied in highest amount • Most costly nutrient • Crop suscep=ble to misuse
– too liile: low yields – too much: lodging, delay harvest, pests, increased cost, off-‐site pollu=on
• Suscep=ble to the most losses • Overuse can lead to environmental concerns
– water quality – air quality
UC DAVIS University of California
Nitrogen transforma=ons in flooded soils
Buresh et al., 2008
N i t r o g e n Fixa;on
The process by which atmospheric nitrogen is converted to biologically usable forms of nitrogen by microorganisms.
Mineraliza;on The breakdown of organic maier resul=ng in the release of ammonium (NH4) and other nutrients which can be used by plants.
Nitrifica;on The conversion of ammonium (NH4) to nitrate (NO3).
Denitrifica;on The conversion of nitrate (NO3) to nitrogen gas (N2), resul=ng in a loss of plant available N.
Immobiliza;on The assimila=on (tying up) of inorganic N (NH4 and NO3) by microorganisms resul=ng in the nitrogen being unavailable for plant uptake.
A m m o n i a vola;liza;on
The loss of ammonia gas to the atmosphere, following the conversion of ammonium (NH4) to ammonia (NH3).
UC DAVIS University of California
Nitrogen transforma=ons in flooded soils
Buresh et al., 2008
Denitrifica=on • In rice systems N fer=lizer is applied in
an ammonium (NH4) form or a fer=lizer that quickly turns to NH4.
• When a field is flooded the N stays as NH4.
• When a field is drained (or it remains in a unflooded condi=on) the NH4 turns to nitrate (NO3). Both NH4 and NO3 can be taken up by plants.
• When a field is reflooded, the NO3 present in the soil can be lost as gas to the atmosphere.
• We do NOT want fer=lizer N turning to NO3
O2 H+
Flood Water
Oxidized Zone
Reduced Zone
Urea Ammonium Sulfate
Fer;lizer Incorpora;on Zone
O2
NH3 ,N2O, N2
Urea Aqua-‐ammonia Ammonium Sulfate
NO3
Nitrate
NO3
UC DAVIS University of California
Nitrogen: func=on and deficiencies
• Func=on • amino acids • proteins • chlorophyll • enzymes • DNA
• Deficiency • Yellow leaves-‐star=ng with lower leaves • Reduced growth and =llering • Do not confuse with S deficiency
UC DAVIS University of California
Nitrogen: figuring out the rate
• Factors affec=ng N rate – N source and placement – Variety (not different for the main rice varie=es) – Soil – Water management – Climate – Residue management
• Incorpora=ng straw allows for a 25 lb/ac reduc=on in N input
• BUT how do you know how much?
UC DAVIS University of California
Rice yields versus N rate
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UC DAVIS University of California
Rice yields versus N rate Arbuckle burn
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UC DAVIS University of California
Determining the correct rate for your field
150
175 +25
125 -‐25
150
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• Representa=ve check • One pass with +25 and
another pass with -‐25 – Aqua rig vs. combine width
– Flag each pass • Monitor over season • Determine yield with
yield monitor • Do over years and
fields • Keep records
UC DAVIS University of California
N source and placement
Aqua-‐NH3 Aqua-‐NH3 + starter
versus
UC DAVIS University of California
Rice yields versus N rate Arbuckle burn
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UC DAVIS University of California
N source, placement, =ming
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Aqua+starter Aqua
Yield (lb
/ac)
a b • Applying all N as aqua – Increased N use efficiency – Same yield poten=al – At op=mal yields
• Reduce N rate by 10 lb/ac – Cheaper source of N – Early growth (35 DAS) is slightly reduced in some loca=ons
Data: 7 field studies/100 lb N/ac N rate
UC DAVIS University of California
Is a topdress necessary?
Total N N treatment 0 0-0
100 100-0 100 75-25 100 25-75 100 100 AS 150 150-0 150 112.5-37.5 200 200-0 200 150-50
UC DAVIS University of California
Wet seeded conventional grain yield (14% moisture)
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Grain yields (lb ac-‐1)
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2008
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Grower wet seeded no-till
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Grain yields (lb ac-‐1)
Total N applied (lb N ac-‐1)
Willows Preflood Split AS LSD = 1235
UC DAVIS University of California
Is a topdress necessary?
• When the same amount of N is applied, we have not yields being significantly higher with a topdress compared to when it is all applied as aqua.
• Some say “When I topdress I get higher yields”. • That may be because you simply applied more N. The real ques=on is would you have goien higher yields if you had applied that N as preplant?
UC DAVIS University of California
N applica=ons following a herbicide applica=on
• One month aqer plan=ng the soil s=ll has a lot of N – Plants are small and N demand low
• Addi=on of more N during this period will likely have limited impact on plant uptake.
1 mo afer plan;ng
1 mo afer plan;ng
UC DAVIS University of California
Nitrogen source
• When aqua is not an op=on
UC DAVIS University of California
Nitrogen management: the 4Rs • Right rate
– Determined individually • Right source
– As much aqua-‐N as possible – Lowest amount of N in starter as possible
• Right place – Injected 3-‐4 inches below soil surface
• Right =me – All N can be applied just before flooding
• Excep=on: if you plan to apply P late
– No benefit of planning a split N applica=on • Apply if necessary • Excep=on: planning for early season drain event
Phosphorus
• Only 10% of rice soils P deficient • Most growers apply P fer=lizer • Deficiencies are developing
UC DAVIS University of California
Phosphorus: func;on and deficiency
• Func=on • Membrane integrity • Energy storage • Phloem transport
• Deficiency • Stunted dark green plants • Narrow leaves • Reduced =llering • Symptoms oqen diminish with =me
• Delayed flowering
UC DAVIS University of California
• Soil test – Olsen-‐P test (sodium-‐bicarbonate)
• above 6-‐9 ppm – Bray-‐P test not good for CA rice soils
• Plant =ssue test – Y-‐leaf =ssue test.
• 35 DAS • 0.2% P
• Input-‐output P budget
Determining the soil P status
UC DAVIS University of California
Input-‐output P budget • Soil is P bank • P is rela=vely immobile in soils.
– No gas losses – Liile is lost through water – Liile lost by leaching
• Inputs – Fer=lizer
• Outputs – Grain removal (0.52% P2O5) – Straw removal (0.21% P2O5)
UC DAVIS University of California
Input-‐output P budget
• Develop a budget – Inputs (lb/ac of P2O5 as fer=lizer) – Outputs (lb/ac removed in
grain and straw)
– Develop such a budget over 5 yr period – take average
UC DAVIS University of California
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P management, soil P and P budget
• Nega=ve budget = yield response
• Olsen P reflects previous P mgmt.
• Growers applied similar P rates
• Difference: yield
UC DAVIS University of California
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Should you apply?
• High P levels (above 15 ppm) / posi=ve P budget – Apply no P
• Low P soils (below 6 ppm) / nega=ve P budget – Build up soil P
• The rest: P not limi=ng – Apply maintenance rate
• that removed by crop
UC DAVIS University of California
Amount of P removed: Only grain removed
Grain yield (cwt@14%)
P added/removed (lb P2O5/ac) 0 5 10 15 20 25 30 35 40 45 50 55 60 65 70
P balance (lb P2O5/ac) 50 -‐26 -‐21 -‐16 -‐11 -‐6 -‐1 4 9 14 19 24 29 34 39 44 55 -‐29 -‐24 -‐19 -‐14 -‐9 -‐4 1 6 11 16 21 26 31 36 41 60 -‐31 -‐26 -‐21 -‐16 -‐11 -‐6 -‐1 4 9 14 19 24 29 34 39 65 -‐34 -‐29 -‐24 -‐19 -‐14 -‐9 -‐4 1 6 11 16 21 26 31 36 70 -‐37 -‐32 -‐27 -‐22 -‐17 -‐12 -‐7 -‐2 3 8 13 18 23 28 33 75 -‐39 -‐34 -‐29 -‐24 -‐19 -‐14 -‐9 -‐4 1 6 11 16 21 26 31 80 -‐42 -‐37 -‐32 -‐27 -‐22 -‐17 -‐12 -‐7 -‐2 3 8 13 18 23 28 85 -‐44 -‐39 -‐34 -‐29 -‐24 -‐19 -‐14 -‐9 -‐4 1 6 11 16 21 26 90 -‐47 -‐42 -‐37 -‐32 -‐27 -‐22 -‐17 -‐12 -‐7 -‐2 3 8 13 18 23 95 -‐50 -‐45 -‐40 -‐35 -‐30 -‐25 -‐20 -‐15 -‐10 -‐5 0 5 10 15 20 100 -‐52 -‐47 -‐42 -‐37 -‐32 -‐27 -‐22 -‐17 -‐12 -‐7 -‐2 3 8 13 18 105 -‐55 -‐50 -‐45 -‐40 -‐35 -‐30 -‐25 -‐20 -‐15 -‐10 -‐5 0 5 10 15 110 -‐57 -‐52 -‐47 -‐42 -‐37 -‐32 -‐27 -‐22 -‐17 -‐12 -‐7 -‐2 3 8 13
Maintenance line
P budget calculator
P budget calculator
P budget calculator: Printout
When to apply:
• Before plan=ng – Use P source with lowest N content – Incorporate
• Timing to control algae – Applica=on of P before plan=ng can lead to algae – Algae reduces crop density and growth
UC DAVIS University of California
UC DAVIS University of California
P management and algae control
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Grower 1 Grower 2
Algae dry weight (g/m2)
At plan=ng (on surface)
Spring applied (incorporated)
30 days aqer plan=ng • Early applica=on and incorpora=on reduced algae 53% on average
• Delayed applica=on decreased algae by 88% on average
When to apply: Grain yield response to delayed P applica=ons
UC DAVIS University of California
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Delayed P applica=on effects on water quality
Days after delayed P application0 5 10 15 20 25 30
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er P
O4-
P (
mg
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Location ALocation BLocation CLocation DLocation E
slope = -‐0.054 mg L-‐1 d-‐1 (P = 0.029)intercept = 0.394 mg L-‐1 (P = 0.3489)
R2 = 0.87
UC DAVIS University of California
Water release
UC DAVIS University of California
Phosphorus management: the 4Rs
• Right rate – Based on soil test and P budget
• Right source – P fer=lizer with lowest N content
• Right place – Incorporated: when applied before flooding – Broadcast: late applica=on into water
• Right =me – Maintenance rates: flexibility – Deficient soils: between land prep and 30 days aqer plan=ng – Algae problems: aqer rice plants emerge (20-‐30 DAP)
UC DAVIS University of California
Potassium: func=on • Plant regula=on
– Osmoregula=on – Enzyme ac=va=on – Regula=on of cell pH – Cellular ca=on-‐anion balance – Regula=on of transpira=on – Regula=on of assimilate transport
• Inadequate K results in: – Adequate K improves a plants ability to tolerate adverse clima=c condi=ons, lodging, insects, and diseases.
UC DAVIS University of California
Potassium: deficiency • Older leaf =ps are yellowish
brown • Younger leaves can be
short and droopy • Rusty brown spots appear
on =ps of older leaves and then spreads to en=re leaf.
• Symptoms tend to appear during later growth stages.
• An accumula=on of sugars and amino acids that are suitable food sources for leaf diseases
UC DAVIS University of California
Potassium and aggregates sheath-‐spot (AgSS)
y = -0.65x + 3.39R2 = 0.58
2.00
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2.80
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1.00 1.20 1.40 1.60 1.80 2.00
Midseason leaf K concentration (% )
AgS
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Incorporated
Removed
Flag leaf K vs. soil K Flag leaf K vs soil K
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Flag leaf K con
centra;o
n (%
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Soil K (ppm)
50% 24%
UC DAVIS University of California
Potassium: loca=ons of low K soils
• East side of valley • Related to soils and irriga=on water
>120 ppm 100-‐120 ppm 60-‐100 ppm <60ppm
Stage Plant Leaf 1
2
3
4
5
Tillering begins
Maximum ;llering
Panicle ini;a;on* Heading R7 Maturity
Fer=lity program for water-‐seeded rice
Starter blend (NPK w/ lowest
amount of N possible)
Aqua-‐N applica;on
Access need for topdress N
applica;on at PI (use urea or AS if needed)
OR before 28 DAS
UC DAVIS University of California
Nutrient management adjustments for different systems
• Drill-‐seeded systems • Stale-‐seed bed systems
UC DAVIS University of California
Drill seeded rice • Right rate
– Similar to water-‐seeded rice for all nutrients
• Right source – Urea plus a starter blend
with P and K if necessary • Right place
– Surface applied • Right =me
– Just before permanent flood – No benefit of applying a
por=on of N rate at plan=ng.
UC DAVIS University of California
Stale seedbed systems
• Stale seedbed – Flush of water to bring up weeds may also increase NO3 accumula=on before flooding
• No-‐=ll – Fer=lizer needs to be applied on the surface
UC DAVIS University of California
Stale seedbed systems • Right rate
– Water seeded-‐increase N rate by 30 lb N/ac. – Drill seeded-‐no change to N rate
• Right source – Urea plus a starter blend with P and K if necessary
Water-seeded
N rate (lb ac-1)
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Drill-seeded
N rate (lb ac-1)
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DS conventionalDS no-till stale
• Right place – Surface applied
• Right =me – Water seeded
• Just before flooding
– Drill-‐seeding • Just before
permanent flood
1. 2. 3. 4. 5. 6.
2%0%
27%
13%10%
48%
Enter ques=on text...
1. Aqua-‐NH3 2. Ammonium sulfate 3. UAN-‐32 (urea-‐
ammonium nitrate) 4. Urea 5. Ammonium
phosphate 6. All the above are
suitable
Clicker ques=on
What is not a suitable N fer=lizer source for flooded rice systems?
UC DAVIS University of California
1. 2. 3. 4.
0%8%
90%
2%
Enter ques=on text...
1. Draining the field is not a problem
2. Draining field reduces root growth and reduces N uptake
3. Draining the field results in ammonium (NH4-‐N) being converted to nitrate (NO3-‐N) which is suscep=ble to loss when the field is reflooded
4. A large amount of N is lost in the tailwater when the flood water is drained from the field
UC DAVIS University of California
Clicker ques=on From a nitrogen management perspec=ve, why is draining the field early in the season a problem?
1. 2. 3. 4. 5.
13%
19% 19%
50%
0%
Enter ques=on text...
1. Before plan=ng 2. 4 weeks aqer
plan=ng 3. 6 weeks aqer
plan=ng 4. 1 & 2 above 5. All the above
Clicker ques=on
When are safe =mes to apply P without risk of yield loss?
UC DAVIS University of California
1. 2. 3.
30%
40%
30%
Enter ques=on text...
1. Nitrogen (N) 2. Phosphorus (P) 3. Potassium (K)
Clicker ques=on
Removing rice straw (i.e. bailing) removes the most of which nutrient?
UC DAVIS University of California
UC DAVIS University of California
THANK YOU
Ques=ons?
UC DAVIS University of California
Nitrogen management: Straw management effects
• Yield poten=al is the same • Incorpora=ng rice straw affects op=mum N rate
– IF incorporated during winter: Fer=lizer N rates can be reduced by 25 lb/ac without compromising yield under straw incorpora=on
– IF leq on surface/standing with no flood: Fer=lizer rates may need to be increased
Yie
ld lb
s/ac
re (1
4% m
oist
ure)
No Flood Winter Flood
Figure 4. Yield of rice grain Maxwell 2000, after 7 seasons of alternative strawmanagement practices.
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