Fertilizer-N (kg/ha)

0 50 100 150 200 250

SPAD

uni

ts

42

44

46

48

50

52

54

56

40 DAP54 DAP70 DAP

Fertilizer-N (kg/ha)

0 50 100 150 200 250

Leaf

col

or in

dex

3.2

3.4

3.6

3.8

4.0

4.2

4.4

4.6

54 DAP

Fertilizer-N (kg/ha)

0 50 100 150 200 250

Leaf

are

a in

dex

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

Fertilizer-N (kg/ha)

0 50 100 150 200 250

Plan

t heg

ht (c

m)

20

30

40

50

60

70

2009

Fertilizer-N applied0 50 100 150 200 250

kg N

/ha

-300-250-200-150-100-50

050

100150200

GrainStoverCropInmediate residualPotential residual 1Potential residual 2

2010

Fertilizer-N applied0 50 100 150 200 250

kg N

/ha

-300-250-200-150-100

-500

50100150200

Inbred maize response to cover crops and fertilizer-N in the southern semi-arid coast of Puerto Rico

MATERIALS AND METHODS• Location was Mycogen Seeds Corp. research farm in Santa Isabel, Puerto Rico. • Soil series are Jacaguas (Loamy-skeletal, mixed, superactive, isohyperthermic

Fluventic Haplustolls) and Fraternidad (Fine smectitic, isohyperthermic Typic Haplusterts)

• Trial 1: Effects of two cover crops and five fertilizer-N levels on maize seed yield response (2008-2009)• Experimental design was a split-plot arrangement of a RCBD with previous

cover crop as the main plot and N level as sub-plot, with four replicates.• Cover crop treatments of: fallow, velvetbean (Mucuna prurience) or cowpea

(Vigna unguiculata var Iron Clay), summer-fall 2008.• After 140 days of growth, cover crops were sprayed with glyphosate and

incorporated via disking into the soil in late September 2008. • Fertilizer-N levels of: 0, 112, 150, 186, and 228 kg N/ha; 50 kg N/ha pre-plant and

the remainder applied via fertigation, fall-winter 2008-2009.• All subplots received 67, 112, and 28 kg/ha of P2O5, K2O and ME (minor element

mixture), respectively.• Inbred maize line A1 was sown on 10 December 2008, grown to maturity and

harvested at about 91 DAP.

• Trial 2: Effect of five fertilizer-N levels on maize seed yield (2009-2010)• Experimental design was a RCBD with five treatments (N levels) and four

replications.• Previous cropping was maize.• Fertilizer-N levels of: 0, 84, 125, 168, 211 kg N/ha; 28 kg N/ha pre-plant and the

remainder applied via fertigation, winter 2010.• Inbred maize line B1 was sown on February 2010, grown to maturity and

harvested at about 91 DAP.• All plots received 63, 14, and 26 kg/ha of P2O5, K2O and ME (minor element

mixture), respectively.

1 - The inbred code is propietary information of Dow Agrosciences LLC

• Irrigation was applied via drip irrigation following farm recommendations.• Soil preparation prior to maize planting included chisel plowing and disking.• Agronomic data gathered included: indicator leaf N concentration, SPAD

chlorophyll meter (Minolta Corp.), plant height, leaf area index, and leaf color index (color chart with scale of 1 to 4).

• Nutrient use efficiency indicators [difference method (DM)]• AEY-DM = (YGf – YGu)/Na

• AEBY-DM = (BYf – BYu)/Na

• ARE-DM = (NBYf – NBYu)/Na

Where AE is the Agronomic Efficiency; ARE is the Apparent Recovery Efficiency; Na is the fertilizer-N applied; YGf and YGu is the grain yield in fertilized and unfertilized crop, respectively; BYf and Byu is the biomass in fertilized and unfertilized crop, respectively; NBYf , and NBYu are the whole plant biomass N in fertilized and unfertilized plants, respectively.

• Nutrient use efficiency indicators [balance method (BM)]• PFP-BM = YGf/Na

• PBP-BM = NGf/ Na

• AE = NBYf /Na

Where PFP is the Partial Factor Productivity; PBP is the Partial Balance Productivity; AE is the Agronomic Efficiency; NGf is the grain N uptake in fertilized crop.

David Sotomayor-Ramirez*1, Randy Huckaba2, Ricky Barnes2, Ronald Dorcinvil3, Jesus Espinosa1

1 College of Agricultural Sciences, University of Puerto Rico, Mayagüez2 Dow AgroSciences LLC, Mycogen Seeds, Puerto Rico

3 North Dakota State University*Contact author: david.sotomayor@upr.edu

This research was supported by the Univ of Puerto Rico, Agricultural Experiment Station and Dow AgroSciences LLC

Table 5. Treatment means of selected N use efficiency indicator parameters of inbred maize during 2008-2009 and 2009-2010. Means with different letters are significantly different (P<0.05).

OBJECTIVES• Determine optimum inbred maize seed yield response to antecedent

cover crop and fertilizer-N addition• Assess the effectiveness of agronomic predictors of crop nitrogen

(N) sufficiency status• Estimate potential N losses in the inbred maize production systems

Figure 1:Scatter plots of the effect of fertilizer-N on N sufficiency indicators for inbred maize during 2008-2009 (Trial 1).

Table 2. Effect of fertilizer N on selected agronomic parameters of inbred maize during 2008-2009 (Trial 1). Means with different letters are significantly different (P<0.05).

Table 3. ANOVA summary to examine the effect of fertilizer N levels on yields and selected agronomic parameters of inbred maize during 2009-2010 (Trial 2)

RESULTS AND DISCUSSIONTable 1. ANOVA summary to examine treatment effects on yields and selected agronomic parameters of inbred maize during 2008-2009 (Trial 1).

ASA-CCSA-SSSA Annual Meeting, 2011 Poster # 310

CCN Level

CC * N Level

Contrast between control and others Fertilizer N Unfertilized control)

Effect ---------Significance level (P)------------- Mean SE Mean SESeed yield (kg/ha 0.016 <.001 ns <0.001 2,726 87.3 1,788 177.5Stover wt (kg/ha) ns <.001 ns <0.001 6,620 107.4 5,690 178.6Ears/ha ns ns ns nsHarvest index 0.009 0.022 0.090 <0.001 0.26 0.01 0.21 0.01Plant biomass (grain + stover) dry wt (kg/ha) ns <.001 ns <0.001 9,346 151.2 7,474 294.1Stover N (kg/ha) ns <.001 ns <0.001 107.9 1.9 83.0 3.8Grain N concentration (%) ns ns ns nsGrain N uptake (kg/ha) 0.080 0.006 ns <0.001 39.7 1.5 25.7 3.0Crop (stover + grain) N uptake (kg/ha) ns <.001 ns <0.001 149.3 2.8 110.4 5.8SPAD chlorophyll reading (40 DAP) ns <.001 ns <0.001 50.6 0.4 43.1 0.7SPAD chlorophyll reading (54 DAP) 0.361 <.001 ns <0.001 53.4 0.4 50.7 0.5SPAD chlorophyll reading (70 DAP) 0.009 0.030 ns <0.001 54.3 0.2 52.6 0.5Leaf color index (54 DAP) ns <.001 0.009 <0.001 4.2 0.1 3.3 0.1LAI (40 DAP) ns <.001 0.008 <0.001 1.05 0.02 0.82 0.04LAI (54 DAP) ns <.001 ns <0.001 1.71 0.03 1.47 0.05LAI (70 DAP) ns 0.012 ns <0.001 1.64 0.03 1.40 0.06Plant height (cm), (40 DAP) <.001 <.001 ns <0.001 33.8 0.4 26.4 0.7Plant height (cm), (54 DAP) ns <.001 ns <0.001 59.5 0.8 48.0 1.1Plant height (cm), (70 DAP) ns 0.002 ns <0.001 64.2 1.1 59.9 1.3

N level Seed yield Stover wt Harvest index

Crop (grain + stover) dry wt Stover N Grain N uptake

Crop (stover + grain) N uptake

Mean SE Mean SE Mean SE Mean SE Mean SE Mean SE Mean SE

--------------------------------------------------------------------------------------------kg/ha-----------------------------------------------------------------------------------------

0 1,788 177.5 B 5,690 178.6 B 0.21 0.01 B 7,474 294.1 B 83.0 3.8 B 25.7 3.0 B 110.4 5.8 B

112 2,708 173.9 A 6,754 176.2 A 0.25 0.01 AB 9,462 288.6 A 108.3 3.7 A 39.2 3.0 A 149.3 5.6 A

149 2,592 173.7 A 6,488 174.9 A 0.25 0.01 AB 9,080 287.7 A 100.4 3.7 A 38.4 3.0 A 140.5 5.6 A

186 2,727 173.7 A 6,538 174.8 A 0.26 0.01 A 9,265 287.7 A 109.5 3.7 A 39.8 3.0 A 151.1 5.6 A224 2,875 177.2 A 6,700 178.3 A 0.26 0.01 A 9,579 293.5 A 113.2 3.8 A 41.5 3.0 A 156.4 5.8 A

Effect Pr > F

Contrast between control and others (P =) Mean SE

Seed yield (kg/ha ns 0.035 n/aStover wt (kg/ha) ns ns 4,567 216.4Ears/ha ns ns 74,599 1,116Harvest index ns ns 0.269 0.017Plant biomass (grain + stover) dry wt (kg/ha) ns ns 5,958 213.2Stover N (kg/ha) ns ns 51.3 3.4Stover P (kg/ha) ns ns 13.3 0.8Stover K (kg/ha) ns ns 99.0 5.4Grain N concentration (%) ns ns 1.46 0.03Grain N uptake (kg/ha) ns 0.064 n/aGrain P uptake (kg/ha) ns 0.035 n/aGrain K uptake (kg/ha) 0.068 0.012 n/aCrop (stover + grain) N uptake (kg/ha) ns ns 68.3 3.4Crop (stover + grain) P uptake (kg/ha) ns ns 17.8 0.8Crop (stover + grain) K uptake (kg/ha) ns ns 103.8 5.4SPAD chlorophyll reading (V5) ns ns 44.6 0.9SPAD chlorophyll reading (R1) 0.086 0.009 n/aLeaf color index (V5) 0.017 0.030 n/aLeaf color index (R1) 0.097 0.056 n/aPlant height (cm), (V5) ns ns 13 0.4Plant height (cm), (R1) ns ns 39 0.4

N level Seed yield SPAD (R1) Leaf color index (V5) Leaf color index (R1)

Mean SE Mean SE Mean SE Mean SE-----------------kg/ha------------0 1,181 101.8 B 49.0 0.6 B 3.1 0.1 C 3.3 0.1 B84 1,449 99.4 AB 51.1 0.6 A 3.2 0.1 BC 3.4 0.1 B125 1,308 101.8 AB 50.8 0.6 AB 3.2 0.1 BC 3.5 0.1 AB168 1,522 99.4 A 51.4 0.6 A 3.5 0.1 AB 3.7 0.1 A211 1,495 98.6 A 51.3 0.5 A 3.7 0.1 A 3.6 0.1 AB

---------------------------------------Mean of fertilized treatments ------------------------------------1,446 56.7 51.1 0.3 3.41 0.1 3.6 0.1

AEY-DM AEBY-DM ARE-DM PFP-BM PBP-BM AE-BMN level Mean SE Mean SE Mean SE Mean SE Mean SE Mean SE--------------------------------------------------------------------2008-2009---------------------------------------------------------------------112 9.1 1.6 A 16.9 2.0 A 0.35 0.05 A 24.4 1.1 A 0.35 0.02 A 1.32 0.03 A

149 6.2 1.6 AB 10.5 2.0 AB 0.21 0.05 B 17.6 1.1 B 0.26 0.02 B 0.93 0.03 B

186 5.7 1.6 AB 9.3 2.0 B 0.22 0.05 AB 14.9 1.1 BC 0.22 0.02 BC 0.81 0.03 C

224 4.9 1.6 B 8.4 2.0 B 0.20 0.05 B 12.6 1.1 C 0.18 0.02 C 0.69 0.03 C

--------------------------------------------------------------------2009-2010-----------------------------------------------------------------84 3.4 0.6 A ---1 ---1 17.5 0.6 A 0.21 0.01 A 0.81 0.07 A

125 0.7 0.6 B 10.2 0.6 B 0.13 0.01 B 0.53 0.07 B

168 1.9 0.6 AB 9.0 0.6 BC 0.11 0.01 BC 0.44 0.07 B

211 1.5 0.6 AB 7.1 0.6 C 0.09 0.01 C 0.36 0.07 B

mean of N levels (2010 only) 1.2 2.3 0.05 0.03

Table 4. Treatment means of selected N indicator parameters of inbred maize during 2009-2010. Means with different letters are significantly different (P<0.05) (Trial 2).

Trial 1• Maize yields (kg/ha) were highest following velvet bean (2,903) and cowpea

(2,522) and the latter was similar to fallow (2189). In general, the cover crops positively influenced the agronomic indicators.

• Seed yield in the fertilizer-N range of 112 to 224 kg N/ha was 34% higher than unfertilized maize.

• No significant difference was observed among fertilizer-N levels in the range of 112 to 224 kg/ha for stover weight, harvest index, plant biomass, stover N, grain N uptake, crop N uptake, and these were higher than the control (no fertilizer-N).

• The SPAD chlorophyll meter, leaf color index and leaf area index were suitable indicators of N sufficiency.

Trial 2• Seed yield in the fertilizer-N range of 84 to 211 kg N/ha was 18% higher than

unfertilized maize.• No significant treatment effects were observed for most agronomic

parameters (marked in red)• The SPAD chlorophyll reading at R1 growth-stage adequately separated out

the control (mean of 49.0) from the fertilized plots (mean of 51.1).• The leaf color index taken at both V5 and R1 growth-stage significantly

identified treatment differences between the control and the fertilized plots.Explanation of termsCrop = grain N + stover NImmediate residual = crop N - fertilizer N Potential residual 1 = crop N - (fertilizer N + stover N)Potential residual 2 = crop N - (fertilizer N + stover N + soil N supply (estimated from crop N uptake)

Figure 2. Nitrogen budget for 2008-2009, Trial 1

CONCLUSIONS• Optimum crop response at fertilizer-N between 88 and 112 kg N/ha.

• Further refinement of these values should be done using varying genetic materials (possibly classified as low- , medium-, and high-yielders).

• N-use efficiency and N balance data shows:• Low fertilizer-N use efficiency, and harvest index• Crop N extraction (63 to 75 kg/ha and 110 to 156 kg/ha)• High immediate and potential residual soil N that increases

beyond critical fertilizer-N rate• Can use agronomic plant sufficiency diagnostic tools such as plant

height, indicator leaf N concentration, leaf color, SPAD chlorophyll index, possibly pre-plant soil nitrate

N budget• Higher nutrient uptake in Trial 1 than Trial 2• Crop N uptake was low, with grain N about 30% of

that in crop.• Immediate residual N, is the fertilizer-N not taken

up by the crop, and is that which remains in soil after harvest.

• Potential residual N 1, is the immediate residual N plus that from stover N mineralization.

• Potential residual N 2, is the excess N in soil considering stover N mineralization, soil profile N, and soil N mineralization.

• Excess N increases with higher fertilizer-N.