Presentation on theme: "Yield Gap Studies through Comparative Performance Analysis (CPA) Presented are : Current problems, mandate and methods. Concepts to study sustainability."— Presentation transcript:
Yield Gap Studies through Comparative Performance Analysis (CPA) Presented are : Current problems, mandate and methods. Concepts to study sustainability aspects of agricultural land use systems. A case study to demonstrate CPA. Dr. C.A.J.M. de Bie ITC, Enschede, The Netherlands Commission VII, Working Group VII/2.1 on Sustainable Agriculture Pre-Symposium Tutorial Title
Good yields Nutrient removals Soil degradation Falling Yields The Poverty Trap High population Shorter or no fallow periods Low yields Persistent soil degradation Expansion onto unsuitable soils The downward spiral to the poverty trap Increasing population Current problems, mandate and methods 1.Poverty Trap
Trends Problems Needs Increase in cultivated area Intensification (crops/ha; stocking density) Heavier natural vegetation exploitation Competition for same tract of land Declining yields Land and natural vegetation degradation Assessment which land uses are relevant for which tracts of land and present needs Assessment by land use type, which management minimizes environmental impacts while maximizing productivity Land Use Declining yields Land and natural vegetation degradation Assessment by land use type, which management minimizes environmental impacts while maximizing productivity Sustainability Study Goals Trends
Fact: Detailed and reliable quantitative information on present land use is scarce and often of low quality. We need good land use data : We need practical concepts and approaches : to gather, manage, classify and map land use information. to study various aspects of present day land use systems. to address questions as put on record by the UNCED conference in Rio (1992; Agenda 21, Chapter 10), e.g.: to identify options to solve future food requirements. to understand and combat environmental degradation. Our Mandate to study “Sustainable Agriculture”. Mandate
Current “Land Evaluation” study method. Based on generic crop-specific factor rating tables. Typically ignores management effects. Does not truly evaluate land use. Evaluates “crops”. Lack of method ? LE
Current “Yield Gap” study entries. Considers levels ‘fixed’; it omits variability between sites/areas. Yield Gap
Current “Management-Yield” study approaches. Based on technology transfer. Focused on only few management aspects at a time. Expensive. Based on knowledge. Management typically excluded. Limited operational use. Lack of method ? Conv.- Simul.
Impact on land ( + or - ) Decision making / planning Requirements & Suitability Productivity Impact on/from the environment Interaction with secondary production systems The Concepts The “Land Use System” (LUS) with ‘study entries’. 2.The Concepts
Failure to distinguish between the two has created much confusion. Land cover is a part of land, whereas land use is not. Some examples: The cover "forest" is identified by its physical components such as vegetation structure, height, density, and extent. The use of “forest” is dictated by its purpose(s) like: rubber production, conservation, recreation, timber production, or shifting cultivation. The land cover “grassland”, distinguished by the presence or dominance of grass (herbaceous vegetation) may be used for hay production, grazing, recreation, etc. Land cover is defined as: "The vegetation (natural or planted) or man made constructions (buildings, etc.), which occur on the earth surface … …”. Land use is defined as: “A series of operations on land, carried out by humans, with the intention to obtain products and/or benefits through using land resources”. Land cover can be determined by direct observation. Obtaining land use information requires communication with the land user. What is Land Cover and what is Land Use ? Cover/Use
- climate - weather - landform - terrain - soil - flora (incl.crops) - fauna - results of past land use (incl. infrastructure) Implements used Inputs Outputs Land Use System LandLand Use Purpose(s) Aimed at [Species/Services - Products/Benefits] combinations. Operation Sequence Details on Operations Impact on land ( + or - ) Repetition … Land problems: limits growth reduces yields Land use aims to modify land to reduce land problems Repetition
Operation Sequences GrazingFallowing 19891988197519691979 Rainfed Cropping JFMAMJJASOND 1988 1989 Observations Operations … many aim to control growth limiting, and yield reducing land aspects. … many relate to growth limiting, and yield reducing land aspects. Ploughing HarvestingFallow Pest Attack Germination Trampling Hail Storm Rill Erosion Weeding Seeding NPK Applic. Illustrating land use operations and land obser- vations The “Operation Sequence” impacts on ‘sustainability’ aspects. Land Use Land Land Use System Oper.Seq.
Yield they address: growth limiting yield reducing land modifying aspects of LUSs. Feasible Problems Management Plot-to-plot variability Problems What do sustainability studies do ? CPA relates differences in land and management aspects to differences in system performances. CPA uses survey data from many plots. CPA studies this gap. Sust.Studies
A Plot defines spatially a unique Land Use Systems. Holding
A Farm is the unit that controls several Land Use Systems. F.System
Date of image Land use is mapped using crop calendar data and RS-images. Crop Calendar
Interview data Observation by surveyor Photo / Image characteristics 1D-features (tone, color), as related to: crop calendars, cropping patterns and other land use operations Infrastructure 2D-features, such as: field sizes, shapes and patterns internal patterns (textures, grids, mottles) line features 3D-features (on APs): vertical structure no. of layers holding/holder information (profile) site aspects (tenancy arrangement, cadastral no., distance to holding, infrastructures present) land use system (plot) aspects for the period considered: a-priori land use class crops grown / services provided (% of area, numbers, etc.) land use purposes operations (crop calendar / cropping pattern): operation name; species involved; % of plot involved; period / periodicity / duration and task times; main power source labor and material inputs and implements used products / benefits obtained observations by land user: soil related (workability, infiltration rate, fertility status, etc.) weather related (hail storm, dry period, etc.) crop related (pests, diseases, lodging, wilting, etc.) plot size, coordinates, slope, position, etc. crops (residues) and infrastructure present in / around the plot land cover data (crop condition, growing stage, weed incidence, biomass, height) ground cover status (bare soil, mulch, crop residues) specific observations (soil characteristics, tillage condition, erosion status, hydrological aspects, pests / diseases incidence, evidence of grazing) Relevant land use data to survey. Survey Data
Survey data Interview data Performance =f (land, land use ) Function to analyze the surveyed Land Use data. Data on the operation sequence Observations on land (crop) by the surveyor / land user Yield Impact on land e.g. erosion, bulk density, or salinity data Math Function
A CPA example. The impact of land use and land aspects on yields of sticky rice in Phrao, Thailand. Yield reported by farmers (21x) were vali- dated through crop-cuttings. Yields of 63 paddies varied from almost ‘0’ to almost 5500 kg/ha. The CPA study did explain 83% of the shown yield variability. The yields 3.CPA Example
Multi-Temporal TM image analysis…… ……Climate represented in a P-ET o diagram. The multi-temporal NDVI image is used to map different crop calendars ( next slide… ). Multi-Temp.
5000750052000025005000 2500 5000 7500 2140000 2500 5000 7500 2150000 Paddies with low cropping intensity (one crop per annum) Paddies with high cropping intensity (two or three crops per annum) Villages In the Phrao floodplain water flows freely across bunded paddies. Areas with a high cropping intensity could be mapped by using the 3 TM-images. Distance from weirs strongly affects the cropping intensity, drought risk, and yields. If water is available, a second or third crop can be grown after rice. The facts Phrao Map
By site, data on the operation sequence were recorded. Shown are the starting dates by operation. Oper.Seq.
YNNN92893 YNYN22109 YYNN32069 NYNN122605 NYYN52019 NNYN132101 Period of Water Shortage Count Average yields (kg/ha) Establish- ment Vegeta- tive Heading + Flowering Yield formation NNNN193932 Impact of Water Shortage on Yield. N N N N N N N N 19 3932 H2O- Shortage
Impact of Selected Pests and Diseases on Yield. Rice Blast63-64NoneYes Leaf blight10-3437% with RBExclude Brown Leaf Spot18-17NoneYes False smut41-1220% with RBExclude Stem Borers17-12NoneTry Black bugs7-8NoneTry Sheath rot120-No effect Foot rot20-No effect Infection rates (%) Pests / DiseaseFreq. Correlation with yields Inter-Correlations Use in M. Regr. ? Pest/Diseases
Period of lodging Freq. Average rice yields (kg/ha) Average lodging-% During Heading/Flowering15230034(7.5-60.0) During Yield Formation9198821 (12.5-27.5) During Ripening8358520 (12.5-27.5) None3131870 Impact of Lodging on Yield (severity and impact). Lodging
Delayed planting of sticky rice is associated with shorter crop-growing periods that cause in turn lower yields. The crop is photo-sensitive.Other factors cause the ‘noise’. Planting Date
Model estimation through multiple regression. Model Estim.
Quantified break-down of the yield gap by constraint. Yield Gap
0 1000 2000 3000 4000 5000 6000 7000 Yield (kg/ha) farmers fieldsresearch station weeding soil type variety lodging water stress diseases timely planting cropping system Potential Yield Yield Gap Actual Yield Average Yield Through regression analysis: the yield constraints were identified, and impacts by constraint quantified … The results Bar Diagram
Relevant land characteristics: The yield constraints and their relative importance: Advise to local organizations: Final statements on the yield constraints. water shortage (41%) diseases incidence (22%; rice blast / brown leaf spot) late planting (18%) lodging (10%) poor soil condition (8%) Water-loss from paddies, defined by the soil infiltration rate (= site specific) Water shortage, defined by the distance from weirs (= map unit specific) Plant breeders must concentrate on resistance to drought, diseases, and lodging. Extension services are best concerned with water management, timely planting, and control of diseases. The results Conclus ion