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 AUGUST 2021

OVERVIEW

Harvesting of lowland 1st palay and upland palay has just started in most parts of the country. Below normal to near-normal yield is expected in CAR, Ilocos Sur, Pangasinan, Zambales, Nueva Ecija, and Batanes due to prolonged and continuous rainfall brought by Severe Tropical Storm “ISANG” that enhanced the Southwest monsoon during the maturity stage of the crops. Near-normal to normal yield is expected in Ilocos Norte, Aurora, Quezon, Oriental Mindoro, Romblon, Camarines provinces, Albay, Masbate, Catanduanes, Capiz, Cebu, Negros, Eastern Samar, Leyte, Bukidnon, Zamboanga del Norte, Zamboanga del Sur, Davao, Surigao del Norte and Surigao del Sur. In contrast, below normal yield is anticipated in Cagayan Valley, Northern Samar, Bohol, Tagbilaran, Zamboanga Sibugay, Misamis Oriental, General Santos and Cotabato, because the crops suffered moisture stress during their critical stage of growth and development.

Meanwhile, the standing upland palay and lowland 1st palay crops, which were planted in June, and lowland 1st palay planted in July, are faring well in Ilocos Region, CAR, Batanes, Bataan, Nueva Ecija, Aurora, CALABARZON, MIMAROPA, most of Region V, Panay Island, Cebu, Eastern Visayas, Bukidnon, Zamboanga del Norte, Zamboanga del Sur, Davao, and BARMM. However, these palay crops suffered moisture stress in Cagayan Valley, Oriental Mindoro, Palawan, Bohol, Northern Samar, Zamboanga del Sur, General Santos, and Cotobato because of the minimal rainfall received over these areas during the crops’ vegetative and reproductive stages.

The weather systems that affected the country during the month were the Southwest (SW) monsoon, localized thunderstorms, low pressure areas (LPAs), ridge of high-pressure areas (HPAs), easterlies, intertropical convergence zone (ITCZ), and the passage of three (3) tropical cyclones (TCs), namely: Tropical Depression (TD) "Gorio" (Aug 04), Tropical Storm (TS) "Huaning" (Aug 07), and Severe Tropical Storm (STS) "lsang" (Aug 19 – 22). None of these TCs made landfall over the country. However, STS "lsang" slightly enhanced the Southwest monsoon which brought rainfall in some parts of western and central Luzon.

Rainfall assessment for the month showed that below normal to near normal rainfall conditions were experienced in most parts of the country except for some patches of above normal rainfall conditions in Catanduanes, Eastern Samar and CARAGA Region in Mindanao.

REGIONS

Harvesting of upland palay has just started in Ilocos Norte; near normal to above normal yield is expected due to sufficient amount of rainfall during the reproductive period of the crops. Meanwhile, below normal to near normal yield is expected from the early-planted, lowland palay in Ilocos Sur and Pangasinan because of continuous rainfall brought by STS “ISANG”. The standing, delayed-planted upland palay in Ilocos and Pangasinan, as well as the lowland 1st palay are in good crops condition because of sufficient moisture during the month.
Harvesting of upland palay has just begun in Cagayan Valley; below normal yield is expected because the crops suffered moisture stress during their reproductive stage of growth and development. In Basco, the standing crop for delayed planted upland palay and lowland first palay suffered moisture stress condition because of insufficient rainfall received during month.
Harvesting of upland palay had just begun across the region; below normal to near normal harvest may be expected because of the prolonged and continuous rainfall brought by STS “ISANG” that slightly enhanced the southwest monsoon. The standing, delayed-planted upland palay, as well as the lowland 1st palay were in good crops condition because of adequate moisture available during the month.
Harvesting of upland palay has just begun. Below normal to near-normal yield is expected this season because of continuous rainfall brought on by the southwest monsoon during the reproductive and ripening stages of the crops. The standing, late-planted upland palay and lowland 1st palay are currently in good crop condition due to the sufficient rainfall amount received in those areas during the month.
Harvesting of lowland 1st palay in Infanta and upland 1st palay in Tayabas is now ongoing; good to normal yield is expected because the crops were in good condition from reproductive to ripening period. The standing late-planted upland palay, delayed planted lowland 1st palay and lowland 1st palay are faring well because of sufficient rainfall received during the month.
Harvesting of upland palay has just begun in the region. Near-normal to normal yield is expected because of good crop condition throughout its growing period.
Harvesting of lowland 1st palay and upland palay has just begun. Near-normal to normal yield is anticipated because the crops were in good condition from reproductive to maturity stage. Likewise, the delayed-planted upland palay and lowland 1st palay in Masbate are faring well. The delayed-planted, lowland 1st palay in most parts of the region are in good condition because of the sufficient moisture available during the month.
Harvesting of upland palay has just begun across the region. Below normal yield is anticipated in Bohol since rainfall was insufficient from the reproductive to maturity stage. The standing, delayed-planted upland palay and lowland 1st palay in Cebu and Negros are in good crop condition. However, rainfall remained minimal in Bohol so the rice crops may have suffered from moisture stress.
Harvesting of upland palay has just begun. Near-normal to normal yield is expected because of good crop condition throughout its growing period.
Sufficient rainfall received during the month favors the standing delayed-planted upland palay and the July-planted lowland 1st palay due this coming October.
Harvesting of lowland 1st palay in Catarman may have had below normal yield, while upland 1st palay in Catbalogan and Tacloban may have below normal to near-normal yield since crops may have partially recovered during the reproductive period. Likewise, the standing delayed-planted upland palay, the delayed-planted lowland 1st palay and the lowland 1st palay due in October are faring well.
Harvesting of upland palay has just begun. Below normal yield is expected because the crops suffered from moisture stress during the reproductive stage of growth and development. In Zamboanga Sibugay, the standing delayed-planted upland palay and lowland 1st palay suffered from moisture stress due to the minimal rainfall received during the month.
Harvesting of upland 1st palay in Bukidnon has just begun. Good to normal harvest is expected this season because the crops were in good condition from planting to maturity phase. However, in Cagayan de Oro, below normal yield is expected due to insufficient moisture during the reproductive stage. The standing delayed-planted, upland palay and the lowland 1st palay due this coming October in Bukidnon are in good condition because of sufficient moisture available during the month, but the crops in Misamis Oriental might have suffered from moisture stress.
Harvesting of upland 1st palay has just started across the region; near-normal to normal yield is expected because the crops were in good condition throughout their growing period. Likewise, the standing delayed-planted, upland palay is faring well.
The possibility of planting rice crops in any part of the region is low because of the minimal rainfall received in the area, except in General Santos.
Harvesting of lowland 1st palay has just started. Good to normal yield is anticipated because the crops experienced sufficient moisture throughout their growing season. The standing delayed-planted, lowland 1st palay is faring well across the region.
Harvesting of upland palay has just begun. Meanwhile, standing lowland 1st palay due this coming October may have suffered from moisture stress due to 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