An index to rate the quality of no-till systems: validation. Glaucio Roloff

An index to rate the quality of An index to rate the quality of no-till systems:no-till systems:

validationvalidation

Glaucio RoloffGlaucio RoloffFederal University of Latin-American Integration (UNILA)Federal University of Latin-American Integration (UNILA)

Ramiro A. T. LutzRamiro A. T. LutzVetagro Crop ConsultantsVetagro Crop Consultants

Ivo Mello & Marie BartzIvo Mello & Marie BartzBrazilian No-Till Federation (FEBRAPDP)Brazilian No-Till Federation (FEBRAPDP)

55thth WCCA & 3 WCCA & 3rdrd FSD FSD Brisbane 2011 Brisbane 2011

Cooperation FEBRAPDP – ITAIPU BinacionalCooperation FEBRAPDP – ITAIPU Binacional

5th WCCA & 3rd FSD Brisbane 2011 2

NTS Quality Index (NTSQI)• A pioneer index that...

» ...requires testing and validation» ...forecasts potential impacts qualitatively» ...indicates tendencies

No-Till System (NTS) Quality Index


Validation• Within a sustainability context:

... an index is valid if it correctly assesses factors leading to the sustainability of a given scenario

• Index validation (Bockstaller and Girardin, 2003. Agricult. Systems, 76, 639-653)» Scientific basis » Output validity → our focus» Usefulness to the end user

No-Till System (NTS) Quality Index


Validation• Analysis must contend with:

» Cause and effect relations are difficult to establish» Agricultural systems are complex» Linear or linearisable functions should not be expected» Non-normal or unknown data distributions are to be expected

NTSQI validation


NTSQI test• 24 voluntary farmers over 6 small river basins• NTSQI from questionnaire data

NTSQI validation M&M

NTSQI validation• Same farmers, independent parameters:

» Average terrace cross-section area (TC)» Difference between calculated and real TC (DTC)» Organic matter (OM)» Phosphorus (P)» Potassium (K)» Cation exchange capacity (CEC)» Sum of bases (SB)» Average worm population (WP)

5 subsamples per field


NTSQI validation statistics

NTSQI validation• Statistical distribution:

» tested for normality by Shapiro-Wilk at p<0.05• Correlation strengths:

» by Spearman´s δ rank coefficient with bootstrapping


NTSQI validation results

Basic statistics: NTSQI and its indicators

NTSQI RI RD RP TF TA CE BN AT

Average 7.17 0.81 0.71 0.67 0.86 0.63 0.68 0.66 0.61

Coef of Var % 11.7 13.6 26.8 29.9 31.4 57.1 22.1 18.2 39.3

Shapiro-Wilk p 0.20 0.03 0.00 0.19 0.00 0.00 0.00 0.00 0.01

Rotation intensity (RI)Rotation diversity (RD) Crop residue persistence (RP)Tillage frequency (TF)

Terrace adequacy (TA)Conservation evaluation (CE) Balanced nutrition (BN)NTS adoption time (AT)

Non-normal



Basic statistics: Independent parameters

P in mg dm-3

K, SB and CEC in cmolc dm-3

DTC in m2

WN in numbers

P OM K SB CEC DTC WN

Average 18.92 3.39 0.52 8.55 13.33 1.00 7.57

Coef of Var % 66.3 15.9 28.8 10.6 8.1 258,0 146.0

Shapiro-Wilk p 0.00 0.65 0.02 0.79 0.56 0.06 0.00

Non-normal



NTSQI RI RD RP TF TA CE BN ATNTSQI 1.00

RI 0.16 1.00RD -0.22 0.27 1.00RP 0.46 0.53 -0.54 1.00TF 0.56 -0.08 -0.04 -0.10 1.00 TA 0.62 -0.27 -0.45 0.21 0.49 1.00CE 0.44 -0.28 -0.18 0.04 0.05 0.29 1.00BN -0.11 0.12 -0.51 0.53 -0.45 0.00 -0.05 1.00AT 0.63 -0.03 -0.25 0.33 0.32 0.36 0.43 -0.14 1.00

Rank correlations: NTSQI and its indicators

moderate strong



Rank correlations: NTSQI and its indicators

• NTSQI most strongly correlated to:» tillage frequency (TF)» terrace adequacy (TA)» adoption time (AT)

• NTSQI vs rotations:» only moderately with rotation persistence (RP)» RP negatively correlated with rotation intensity (RI):

– second summer crop (corn) negates winter cover crop



Rank correlations: NTSQI + indicators vs independent

moderate strong

NTSQI RI RD RP TF TA CE BN AT

P 0.34 -0.17 -0.34 0.15 0.19 0.32 0.31 0.14 0.24OM 0.55 -0.12 -0.37 0.30 0.43 0.64 0.09 -0.11 0.57K -0.78 -0.10 0.23 -0.35 -0.56 -0.44 -0.41 0.05 -0.55

DTC -0.30 -0.08 0.03 -0.06 -0.38 -0.32 0.14 0.31 -0.38WN 0.21 0.45 -0.10 0.49 0.03 -0.04 -0.19 0.31 0.04

CEC and SB were not correlated to any NTSBI indicator:...withdrawn from further analysis



Rank correlations: NTSQI + indicators vs independent

• NTSQI correlated to most independent parameters:» exception - worm numbers (WN)» potassium content (K) is an oddball

• Organic matter (OM) correlations:» strongly with NTSQI, terrace adequacy (TA) and

adoption time (AT)» moderately with rotation diversity (RD), rotation

persistence (RP) and tillage frequency (TF)



Conclusions:

• NTSQI is a valid index from an output point of view.…. at this preliminary stage

• NTSQI methodology:» can pinpoint practices that need to be targeted» hence will improve NTS's environmental services


Thank youThank you

[email protected]@unila.edu.br

55thth WCCA & 3 WCCA & 3rdrd FSD FSD Brisbane 2011 Brisbane 2011

An index to rate the quality of no-till systems: validation. Glaucio Roloff

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