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 OCTOBER 2021

OVERVIEW

Harvesting of lowland 1st palay has just started in most parts of the country. Due to occurrences of heavy rainfall (most of which were induced by the passage of Severe Tropical Storm “MARING” and Tropical Depression “Lannie”) mature and harvestable crops may have been damaged in Ilocos Sur, Abra, Kalinga, Benguet, Cagayan, Nueva Vizcaya, Bulacan, Tarlac, Zambales, Quezon, Rizal, Cavite, Palawan, parts of MIMAROPA, Zamboanga Peninsula, and CARAGA. Standing dry season palay and non-mature wet season palay in Eastern Visayas, Zamboanga Peninsula, Northern Mindanao, and Lanao del Sur may have also been damaged by the occurrence of heavy rainfall.

Heavy rainfall that caused flooding may have also hindered the establishment or land preparation activities for 2nd planting season of corn in Ilocos Region, CAR, Cagayan Valley, Central Luzon, CALABARZON, MIMAROPA and Bicol Region. In these regions (except MIMAROPA and Bicol Region), heavy rainfall possibly damaged the 3rd planting season corn in the vegetative stage. The same may have happened to the 2nd planting season corn, curently in flowering stage, in Negros Occidental, Iloilo, Eastern Visayas, Zamboanga Peninsula, Northern Mindanao, and CARAGA. Generally, and for surviving crops in areas affected by heavy rainfall, the moisture for the month had been sufficient for the rainfed crops in Catanduanes, Camarines Sur, Negros Occidental, Bohol, Leyte, Zamboanga Sibugay, Misamis Oriental, Lanao del Norte, Davao del Norte, Compostella Valley, and Lanao del Sur.
The weather systems that affected the country during the month were the Southwest (SW) monsoon, localized thunderstorms, low pressure areas (LPAs), easterlies, intertropical convergence zone (ITCZ), and the passage of three (3) tropical cyclones (TCs), namely: Tropical Depression (TD) “LANNIE” (Oct. 4 – 6), Severe Tropical Storm (STS) “MARING” (Oct. 8 – 12) and Tropical Depression (TD) “NANDO” (Oct. 9). TD “LANNIE” made landfall and brought heavy rainfall, which caused flooding in MIMAROPA and Region 6 while STS “MARING” did not landfall but enhanced the Southwest monsoon which brought moderate to heavy rainfall and caused flooding and landslide in Region 1, Region 2, Region 3, MIMAROPA, CARAGA and CAR with an estimated cost of damage to agriculture amounting to ₱3,267,218,527.47 based on NDRRMC Sitrep no. 15 on STS “MARING” (2021).
Rainfall assessment for the month showed that near to above normal rainfall conditions were experienced in most parts of the country except for Central Luzon, where below normal rainfall conditions were observed.

REGIONS

Harvesting of lowland first palay is ongoing. Mature crops in the norther part of Ilocos Sur may have been damaged due to heavy rainfall if not harvested earlier.

Establishment or land preparation stage for the 2nd planting season corn has generally started, however, the occurrence of heavy rainfall might have hindered the activity. The 3rd planting season corn is in the vegetative stage, and thus, may have also been affected by heavy rainfall.
Harvesting of lowland first palay has started. The southern part of Cagayan, northern part of Isabela and the eastern part of Nueva Vizcaya were affected by heavy rainfall, which may have damaged the mature crops in said areas if not harvested beforehand.

Establishment or land preparation activity for the 2nd planting season corn has also started, however, heavy rainfall may have adversely affected the activity. Corn in the 3rd planting season is in the vegetative stage, and thus, may have also been affected by heavy rainfall.
Harvesting of lowland first palay is ongoing. The western part of Abra, northeastern part of Kalinga and southern part of Benguet were affected by heavy rainfall, which may have damaged the mature crops in said areas if not harvested beforehand.

Establishment or land preparation activities for the 2nd planting season corn have started; however, the occurrence of heavy rainfall may have hampered the farming activity. Meanwhile, the 3rd planting season corn crops that are in the vegetative stages, might have also been affected by heavy rainfall.
Harvesting of lowland first palay is ongoing. The southern part of Bulacan and parts of Tarlac and Zambales have been affected by heavy rainfall, which may have damaged the mature crops in said areas if not harvested beforehand.

Establishment or land preparation activities for the 2nd planting season corn has generally started, however, heavy rainfall events might have hindered these farming activities. Corn in the 3rd planting season is in the vegetative stage, and thus, may have also been affected by the heavy rainfall occurrence.
Harvesting of lowland first palay is ongoing. Below normal yield is anticipated as the parts of Quezon province, most of Rizal, and most of Cavite have been affected by heavy rainfall. Potential damage to the mature crops in said areas might have been experienced.

Establishment or land preparation activities for the 2nd planting season corn has also started, however, heavy rainfall event might have hindered the activity. Corn in the 3rd planting season is in the vegetative stage, and thus, may have also been adversely affected by heavy rainfall.
Harvesting of lowland first palay is ongoing. The northern part of Palawan mainland had been affected by heavy rainfall, which may have damaged the mature crops in said areas if not harvested beforehand.

Establishment or land preparation stage for the 2nd planting season corn has generally started, however, heavy rainfall activity may have hindered the activity.
Harvesting of lowland first palay is ongoing. Below normal yield is possible due to the heavy rainfall induced by the passage of STS Maring and TD Lannie.
The 2nd planting season corn are in the flowering stage. These crops in all parts of the region may have been damaged due to heavy rainfall brought by the passage of TD Lannie.
The 2nd planting season corn are in the flowering stage. These crops, particularly in Negros Occidental and parts of Iloilo may have been damaged due to heavy rainfall.
Dry season palay are in the nursery stage. These crops in most of Eastern Visayas (especially Southern Leyte) may have been damaged due to heavy rainfall brought by the passage of TD Lannie. Meanwhile, the 2nd planting season corn in flowering stage may have also been damaged by the heavy rainfall.
Harvesting of lowland first palay is ongoing, while dry season palay are now in the vegetative stage. The entire Zamboanga Peninsula (except for Isabela) had been affected by heavy rainfall, which may have damaged the vegetative and mature crops.

Potential damage to the 2nd planting season corn, currently in flowering stage, may have also occurred because of heavy rainfall.
Harvesting The wet season palay are now in the reproductive/flowering stage. Most of Northern Mindanao had been affected by heavy rainfall, which may have damaged the standing crops.

Additionally, the 2nd planting season corn in flowering stage may have also been damaged by the occurrence of heavy rainfall.
Most parts of the region, except for the western and southern part, have been affected by heavy rainfall. Generally, there might be no ongoing farming activity during the month.

The monthly rainfall is sufficient for the rainfed crops in Davao del Norte and Compostella Valley, excess in Davao Oriental, and inadequate in Davao del Sur.
The wet season palay are now in the reproductive/flowering stage. Rainfall during the month may be insufficient to support the crops in all stages.
Harvesting of lowland first palay is ongoing while the dry season palay are now in nursery stage. Most of CARAGA have been affected by heavy rainfall, which may have damaged the standing crops including the 2nd planting season corn in flowering stage.

For the surviving crops, moisture for the month is generally sufficient for all stages.
The dry season palay are now in nursery stage. These crops, particularly in most of Lanao del Sur may have been damaged by heavy rainfall. Otherwise, the available moisture had been sufficient for the crops in the province, while the other parts of the region have had insufficient rainfall.

Ten Day Rainfall Distribution

Monthly Rainfall Distribution

Generalized Moonsoon Index

Tropical Cyclone

Actual Rainfall and Potential Evapotranspiration

Stations

For Particulars, please contact:

DR. MARCELINO Q. VILAFUERTE II


OIC, Impact Assessment and Applications Section (IAAS)

Climatology and Agrometeorology Division (CAD), DOST-PAGASA

Trunkline No.: (02)8284-0800 (Loc. 904)

E-mail: mvillafuerte@pagasa.dost.gov.ph