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 JANUARY 2021

OVERVIEW

Harvesting of early-planted dry season corn has now started in some areas of the country. Good to above normal yield is expected in portions of CAR, in Tayabas, Ambulong, Bukidnon, and Bohol. Meanwhile, the late-planted lowland 2nd palay and vegetating dry season corn remain in good condition due to sufficient moisture in Nueva Ecija, Aurora, portions of Quezon Province, portions of Bicol Region, and Misamis Oriental. The same crops may have likely suffered from moisture stress due to insufficient rainfall in Ilocos Sur, Ilocos Norte, portions of CAR, portions of Central Luzon, portions of MIMAROPA, and portions of Central Visayas.

Sufficient rainfall enables planting activities to commence in most of Central Visayas, in Zamboanga del Norte, Davao Region, and Butuan. In contrast, these activities are prevented by excessive moisture in Northern Samar, Surigao, and Hinatuan; and by insufficient rainfall in Zamboanga del Sur, SOCCSKSARGEN, and BARMM.

The weather systems that affected the country during the month were the Northeast (NE) monsoon, low pressure areas (LPAs), intertropical convergence zone (ITCZ), localized thunderstorms, easterlies and tail-end of frontal systems (TEFS) or shear line. No tropical cyclone entered the Philippine Area of Responsibility (PAR).

REGIONS

Moisture from rainfall remains insufficient in the area, and crops that survive towards the vegetative stage in Ilocos Sur and Ilocos Norte have likely suffered from moisture stress.
Except in Batanes, the late-planted 2nd palay and dry season corn are suffering from moisture stress due to insufficient rainfall.
Harvesting of early-planted dry season corn has now started in the region. Meanwhile, the late-planted lowland 2nd palay and vegetating dry season corn have likely suffered from moisture stress due to the minimal moisture from rainfall during the month.
The late-planted 2nd palay and dry season corn in Nueva Ecija and surviving crops in Aurora remain in good condition courtesy of the sufficient rainfall during the month. However, for the rest of the region, moisture from rainfall is insufficient which would most likely lead to moisture stress for the vegetative crops.
Harvesting of dry season corn has now started in Ambulong. Meanwhile, the surviving late-planted 2nd palay and dry season corn in the rest of Quezon Province are in good crop condition.
The late-planted 2nd palay and dry season corn in most parts of the region received minimal rainfall during the month and may be suffering from moisture stress.
The late-planted 2nd palay and dry season corn in vegetative stage throughout the region are now in good condition courtesy of the sufficient rainfall received during the month.
Harvesting of dry season corn has now started in Dauis, Bohol. For the rest of the region, crops in vegetating stage may be suffering from moisture stress due to insufficient rainfall.
Farming activities are still not possible within the region since rainfall remains inadequate.
Planting of late-planted 2nd palay and dry season corn may now be possible in the region due to sufficient rainfall, except in Northern Samar which received excessive rainfall during the month.
Farming activities for late-planted 2nd palay and dry season corn are now possible in Zamboanga del Norte courtesy of the sufficient rainfall amount. However, rainfall in Zamboanga del Sur remains insufficient.
Harvesting of surviving dry season corn has now started in Bukidnon. Meanwhile the vegetating crops in Misamis Oriental are now in good crops condition courtesy of the sufficient rainfall received during the month.
Farming activities for late-planted 2nd palay and dry season corn are now possible in the region courtesy of the sufficient rainfall amount.
Rainfall received in the region remains insufficient, thus further hindering the planting activities for 2nd palay and dry season corn.
Planting activities are still not possible in Surigao and Hinatuan due to the excess rainfall received during the month. Meanwhile, planting activities for late-planted 2nd palay and dry season corn is now possible in Butuan.
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

No Active 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