Impact Assessment for Agriculture
Preface

The Impact Assessment and Applications Section (IAAS) of Climatology and Agrometeorology Division (CAD) regularly issue this monthly/bulletin which will provide users such as food security managers, economic policy makers, agricultural statisticians and agricultural extension officials with qualitative information on the current and potential effects of climate and weather variability on rainfed crops, particularly rice and corn. This bulletin, entitled “Climate Impact Assessment for Agriculture in the Philippines”, represents a method for converting meteorological data into economic information that can be used as supplement to information from other available sources.

For example, an agricultural statistician or economist involved in crop production and yield forecast problems can combine the assessment with analysis from area survey results, reports on the occurrence of pests and diseases, farmers’ reports and other data sources.

The impact assessments are based on agroclimatic indices derived from historical rainfall data recorded for the period 1951 to the present. The indices, expressed in raw values percent of normals and percentile ranks, together with real time meteorological data (monthly rainfall, in percent of normal), percent of normal cumulative rainfall, as well as the occurrence of significant event such as typhoons, floods and droughts are the tools used in the assessment of crop performance. Crop reports from PAGASA field stations are also helpful.


The narrative impact assessment included in the bulletin depicts the regional performance of upland, 1st lowland and 2nd lowland palay; and dry and wet season corn crops, depending on the period or the season. Tabulated values of normal rainfall and generalized monsoon and yield moisture indices are provided for ready reference. Spatial analysis of rainfall, percent of normal rainfall and the generalized monsoon indices in percentile ranks are also presented on maps to help users visualize any unusual weather occurring during the period. The generalized monsoon indices in particular, are drought indicators; hence, the tables (see Appendices) together with the threshold values can be used in assessing drought impact, if there are any. It also helps assess any probable crop failure.

It is hoped therefore that this bulletin would help provide the decision-makers, planners and economist with timely and reliable early warning/information on climatic impact including the potential for subsistence food shortfalls, thereby enabling them to plan alternate cropping, if possible, food assistance strategies/mitigation measures to reduce the adverse impact of climate and eventually improve disaster preparedness.

Impact assessment for other principal crops such as sugarcane and coconut, for energy and for water resources management, are from time to time will be included in the forthcoming issues of this bulletin.


The IAAS of CAD will appreciate suggestions/comments from end-users and interested parties for the improvement of this bulletin.

Definition of Terms
The Generalized Monsoon Index (GMI) helps determine the performance of the rains during the season and serves as a good indicator of potential irrigation supplies. It is a tool used to assess rainfed crops.

The GMI for the southwest monsoon (GMIsw) in an area during June to September is defined as follows:
GMIsw = W6P6 + W7P7 + W8P8 + W9P9

The GMI for the northeast monsoon (GMIne) in an area during October to January is defined as:
GMIne = W10P10 + W11P11 + W12P12 + W1P1

where:

W = weight coefficient of monthly rainfall for the season;
P = rainfall amount in the ith month
(i = 1 for January, 2 = for February, etc.)

The Yield Moisture Index (YMI) is a simple index that helps the users assess agroclimatic crop conditions during the crop season. The YMI for a particular crop is defined as follows:
n YMI =  [Pi Ki] i

where:

i = crop stage (1 = planting/transplanting,
2 = vegetative, 3 = flowering, 4 = maturity, etc.)
n = total no. of crop stages;
P = rainfall during the ith crop stage; and
K = appropriate crop coefficient for the ith crop stage.

Tentatively, the threshold values of categories of indices for interpretation being adopted for both YMI and GMI are as follows:


PERCINTELE RANK INTERPRETATION
> 80 Potential for Flood Damage
41 - 80 Near normal to above-normal crop condition
21 - 40 Moderate drought impact with reduced yield
11 - 20 Drought impact with major yield losses
< 10 Severe drought impact with crop failure and potential food shortages

Agroclimatic / AGROCLIMATIC / CROP CONDITION ASSESSMENT FOR DECEMBER 2020

OVERVIEW

Land preparation, planting and transplanting activities for December-planted lowland 2nd palay as well as dry season corn has started in Baguio, Batanes, Nueva Ecija, Romblon, Coron, Bohol, and Cagayan de Oro owing to the sufficient rainfall received during the month. Planting activities are hampered by inadequate rainfall in most parts of Ilocos Region, Zambales, Zamboanga del Sur, Davao Region, SOCCSKSARGEN and ARMM. Meanwhile, excess rainfall (most of which are brought about by Tropical Cyclone passage and the effect of Low Pressure Areas) has potentially damaged November-planted crops and hindered planting activities in Ilocos Region, Aparri, Tuguegarao, Aurora, most parts of Quezon Province, Calapan, most of Bicol Region, Puerto Princesa, San Jose, Masbate, Eastern Visayas, Negros Oriental, Cebu, Panay Island, Bukidnon, Zamboanga del Norte, Davao Region, and CARAGA.

The weather systems that affected the country during the month were the Northeast Monsoon (NE), low pressure areas (LPAs), localized thunderstorms, enhanced easterlies, tail-end of frontal system (shearline) and the passage of Tropical Storm (TS) “Vicky”. TS “Vicky” crossed the Philippine landmass and brought moderate to heavy rains which caused flooding, landslides and other secondary damages over Region IV-B, V, VI, VII, VIII, IX, X, XII and CARAGA, as contained in the National Disaster Risk Reduction and Management Council (NDRRMC) situational reports.

REGIONS

Land preparation, planting and transplanting activities for lowland 2nd palay and dry season corn across the region during the month may be hampered due to minimal rainfall. For the same reason, the November-planted 2nd palay have likely suffered from moisture stress due to insufficient rainfall.
Persistent flooding due to heavy rains and dam water release hinders planting activities in Cagayan, particularly in Aparri and Tuguegarao. Meanwhile in Batanes, planting activities for 2nd palay and dry season corn were favored by adequate rainfall.
Land preparation, planting and transplanting activities for lowland 2nd palay and dry season corn is possible in Baguio due to sufficient rainfall. For the same reason, the November-planted 2nd palay and dry season corn are faring well.
In Zambales, November-planted 2nd palay and dry season corn have likely suffered from moisture stress due to insufficient rainfall. In contrast, the same crops in Aurora were most likely damaged by waterlogging due to excess rainfall. Meanwhile, in Nueva Ecija, rainfall is sufficient for land preparation, planting and transplanting activities for lowland 2nd palay and is adequate for the November-planted 2nd palay and dry season corn to remain in good condition.
In most parts of Quezon Province, the November-planted 2nd palay and dry season corn were most likely damaged by waterlogging due to excess rainfall. This also probably hindered further planting activities for 2nd palay and dry season corn during the month. Meanwhile, in Ambulong, the same crops remain in good condition due to sufficient rainfall.
In Calapan, Oriental Mindoro and Puerto Princesa, Palawan, November-planted 2nd palay and dry season corn may have been damaged by waterlogging due to excess rainfall. In contrast, the same crops are possibly affected by waterlogging in San Jose, Occidental Mindoro. Meanwhile, planting activities related to the same crops may have just started in Romblon and Coron, Palawan, owing to sufficient rainfall.
Most of Bicol Region received excess rainfall during the month which continued to hinder planting activities for 2nd palay and dry season corn. The same crops planted on November in Masbate may have been damaged by waterlogging due to above normal rainfall.
In Negros Oriental and Cebu, crops may have suffered from waterlogging due to excess rainfall. Meanwhile in Dauis, Bohol, crops remain in good condition owing to sufficient rainfall. This also makes it possible to continue with planting activities for 2nd palay and dry season corn.
Above normal rainfall may have damaged the November-planted 2nd palay and dry season corn in Panay Island. For the same reason, planting activities for both crops may not be possible during the month.
The entire Eastern Visayas received excess rainfall, potentially damaging the November-planted 2nd palay and dry season corn and preventing further planting activities during the month.
Rainfall received in Zamboanga del Sur remains insufficient, thus further hindering the planting of 2nd palay and dry season corn. In contrast, Zamboanga del Norte received excess rainfall during the month which damaged November-planted crops and prevented planting activities.
Land preparation, planting and transplanting activities for lowland 2nd palay and dry season corn in Misamis Oriental are ongoing owing to the sufficient rainfall received by the area during the month. However, in Bukidnon, November-planted dry season corn may have been damage by waterlogging due to excess rainfall.
The excess rainfall received by the Davao Region due to the passage of TS Vicky further hinders the planting activities for 2nd palay and dry season corn.
Rainfall received in the region remains insufficient, thus further hindering the planting activities for 2nd palay and dry season corn.
The excess rainfall received by CARAGA due to the passage of TS Vicky most likely damaged the November-planted 2nd palay and dry season corn and hindered further planting activities.
Rainfall received in the region is insufficient which hinders the planting activities for 2nd palay and dry season corn.

Ten Day Rainfall Distribution

Monthly Rainfall Distribution

Generalized Moonsoon Index

Tropical Cyclone

Actual Rainfall and Potential Evapotranspiration

Stations

For Particulars, please contact:

THELMA A. CINCO


Impact Assessment and Applications Section (IAAS)

Climatology and Agrometeorology Division (CAD)

PAGASA-DOST

Telefax No.: 434-58-82