Crop Estimating Survey on Paddy (Maha) - 2003 - Sri Lanka

Abstract
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Crop estimating survey on paddy which is popularly known as "Crop Cutting Survey" commenced in the year 1950. It is conducted covering Maha and Yala season with a view to estimate the average yield of paddy and production by District. In a Maha season about 6,000 and in a Yala season about 4,000 experiments are being conducted for this survey and it is the only source to estimate the country's paddy production. Policy Planners are benefited by these data in numerous ways for taking the decisions such as volume of additional rice requirement of the country to be imported in time, evaluation of extension programs undertaken to uplift the average yields of paddy, pricing policies of rice, mobilization of stocks from one place to another and many more. Therefore, it is a great responsibility to estimate paddy production accurately and timely to fulfill the national requirement.

Field staff attached to each District has been entrusted with many responsibilities on various data collection activities and among them, method of data collection for crop cutting is different from the other surveys. This survey is associated with an objective approach; as such crop cutting officers should carry out experiments in the field by themselves. According to the standard procedure, the crop cutting officer must visit the selected paddy field and they should follow a number of steps such as; demarcate the specified plot of land equivalent to 16' ½'' X 16' 1/2" (a paddy land of one perch of an acre), harvest the crop of the plot, thresh the grain, measure the grain using standard set of seers and finally report the results through the prescribed form CC3.

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Concepts, Definitions and Classifications associated with Crop Estimation of Paddy Survey

Seasons - In Sri Lanka there are two major cultivation seasons associated with two monsoons and they are known as Maha season and Yala Season.

Maha Season is the main season associated with North-east monsoons effective during September - April in the following year. When a particular crop is planted and harvested during this period is known to be Maha Crop.

Yala season is the secondary season which is associated with South-west monsoons effective during the period between May to September. When a particular crop is planted and harvested during this period is known to be Yala Crop.

Mode of Irrigation
There are three type of irrigations related with paddy cultivation. They are (1). Major Irrigation schemes (2). Minor Irrigation schemes (3). Rain-fed schemes.

Major Irrigation schemes defined to be an irrigated scheme of which water is fed to more than 200 acres otherwise it defines as a Minor Irrigation scheme.

Rain-fed is defined, if the cultivated extent is purely depending on rain water in absence of permanent water tank or reservoir.

Volume of Production is reported in Metric Tons.
Average Yield per acre or Hectare: An Indicator of productivity per area unit (2.471 acres = 1 hectare while 1 hectare is equal to 1,000 square meters) estimated through crop cutting survey. Average yield per acre is reported in Bushels while per hectare is reported in Kgs.

Average yield is expressed in terms of Paddy (grain with the husk form but not in Rice form)

Area Harvested refers to the gross area of which the harvest is gathered excluding the area damaged due to different causes.

Gross Area refers to the extent of which reported by enumerators or respondents based on cultivated extent estimated by seed rates but not based on cadastral surveys while Net Area refers to the extent evolved by deducting the extent set a part for bunds and ridges.

Production for a year should consider to be the sum of the production of Maha season and Yala season. For instance the production of the year 2005 is to be the sum of 2004/05 Maha season and Yala season of 2005.

Geographic coverage
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National Coverage

Analysis unit
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Paddy land Parcel 16 1/2" X 16 1/2", Where smaller experimental plot sizes are used in terraced fields.

Universe
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The survey covered a random sample from all the paddy lands in Sri Lanka

Kind of data
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Sample survey data [ssd]

Sampling procedure
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Sampling Design: The sampling design adopted in the survey is a stratified multistage sampling method where DS Divisions were treated as strata and mode of irrigation schemes namely; Major, Minor, and Rain-fed as sub strata. Number of villages to be selected for crop cutting experiments in each scheme is decided on the basis of the following proportions.

Acreage sown in the previous corresponding season Number of villages to be selected
< 500 Acres 3
500 - <1000 Acres 5
1000 - < 5000 Acres 10
5000 - < 10,000 Acres 15
10,000 - < 15,000 Acres 20
15,000 - < 20,000 Acres 25
20,000 Acres and above 30

Though the recommended design is such, considering the sampling variances occurred during the previous seasons, the number of experimental villages to be selected is being curtailed in order to keep the number of villages within a range of 3,000 for a Maha season and 2,000 for a Yala season in a year. Other reasons for such restrictions were related to practical aspects like cost of the survey and number of personnel that could be deployed to carry out crop cuttings.

In each selected village two crop cutting experiments are conducted. At present the sample villages and the parcels are selected at random. However, prior to 1980, selection of villages as well as parcels was done at random with probability proportional to the area cultivated during the previous corresponding season with replacement. As the procedure was somewhat laborious and time consuming, it was replaced with the present system i.e. both stages at random. Sample villages are selected in the head office while the selections of parcels are done at the respective Districts.

Controlling of Non-sampling Errors: In view of the accuracy of the experimental results, a sample of 1/5 of selected villages are to be supervised by executive officers/District Heads identified from the District such as DS/GA, Divisional Secretary, Director/Deputy Director of Agriculture, Deputy Commissioners of Agrarian Development in addition to the Senior Staff of DCS attached to the District. Spot checks are to be performed by them by visiting the sample villages.

Mode of data collection
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Face-to-face [f2f]

Research instrument
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The questionnaire is Form C.C.3 printed in Sinhala/English and Tamil/English languages. It has three parts.

Part I is about the geographical and Paddy land parcel information.

Part II includes System of tenure, Method of preparation of land, Variety of seed, Method of sowing, Application of Fertilizer, Weeding, Insecticides, Fungicides, Adverse affects on crop.

Part III Collects yield information.

In the questionnaire the above information is recorded for two parcels selected for the survey. The same Form C.C.3 is used to collect data for both Yala and Maha seasons. Maha Season falls during "North-east monsoon" from September to April in the following year. Yala season is effective during the period from May to end of August.

Sampling error estimates
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Formulae needed to calculate Avg. Yield & Variance for a given Stratum is available in the External Resource Section.

摘要
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水稻产量估算调查，通常被称为“作物收割调查”，始于1950年。该调查涵盖马哈和亚拉两个季节，旨在估算水稻的平均产量和各地区的产量。在马哈季节，大约有6,000次实验，在亚拉季节大约有4,000次实验，这是估算国家水稻产量的唯一来源。政策规划者通过这些数据以多种方式受益，以便做出决策，例如及时进口额外大米的需求量、评估提升水稻平均产量的推广计划、大米定价政策、从一地到另一地的库存动员等。因此，准确并及时估算水稻产量以满足国家需求是一项重大的责任。

每个地区的现场工作人员被委托负责多项数据收集活动，其中作物收割的数据收集方法与其他调查不同。该调查采用一种客观的方法；因此，作物收割官员应自行在田间进行实验。根据标准程序，作物收割官员必须访问选定的水稻田，并应遵循以下步骤：划出相当于16' ½'' X 16' 1/2''（一英亩一 perch 的水稻田）的指定地块、收割地块上的作物、脱粒谷物、使用标准套筒测量谷物，最后通过规定的表格CC3报告结果。

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与水稻产量估算调查相关的概念、定义和分类

季节 - 斯里兰卡有两个主要栽培季节与两个季风相关联，它们被称为马哈季节和亚拉季节。

马哈季节是与东北季风相关的主要季节，有效期为当年的9月至次年的4月。在此期间种植和收获的特定作物被称为马哈作物。

亚拉季节是与西南季风相关的次要季节，有效期为5月至9月。在此期间种植和收获的特定作物被称为亚拉作物。

灌溉方式
与水稻种植相关的灌溉有三种类型：(1) 主要灌溉工程 (2) 次要灌溉工程 (3) 降雨灌溉。

主要灌溉工程定义为灌溉面积超过200英亩的灌溉工程，否则定义为次要灌溉工程。

降雨灌溉定义为，在缺乏永久性水罐或水库的情况下，种植面积完全依赖降雨。

产量以公吨为单位报告。

每英亩或公顷的平均产量：通过作物收割调查估计的每单位面积生产力的指标（2.471英亩 = 1公顷，而1公顷等于10,000平方米）。每英亩的平均产量以蒲式耳报告，每公顷以公斤报告。

平均产量以糙米（带壳的谷物，但不是大米形式）表示。

收获面积是指收获的毛面积，不包括因各种原因而受损的面积。

毛面积是指统计员或受访者根据种子率估计的种植面积，而不是根据地籍调查报告的面积，而净面积是指减去为堤坝和脊设置的面积后得到的面积。

一年的产量应考虑为马哈季节和亚拉季节产量的总和。例如，2005年的产量应等于2004/05马哈季节和2005年的亚拉季节的总和。

地理覆盖范围
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全国覆盖

分析单元
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16 1/2" X 16 1/2"的水稻田地块，在梯田中使用较小的实验地块尺寸。

总体
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调查覆盖了斯里兰卡所有水稻田的随机样本

数据类型
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样本调查数据 [ssd]

抽样程序
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抽样设计：调查采用的抽样设计是分层多阶段抽样方法，其中DS分区被视为层，灌溉方式（主要、次要、降雨灌溉）被视为亚层。每个方案中用于作物收割实验的村庄数量根据以下比例确定。

上一季种植面积 要选择的村庄数量
< 500 英亩 3
500 英亩 - <1000 英亩 5
1000 英亩 - < 5000 英亩 10
5000 英亩 - < 10,000 英亩 15
10,000 英亩 - < 15,000 英亩 20
15,000 英亩 - < 20,000 英亩 25
20,000 英亩及以上 30

尽管建议的设计是这样的，但考虑到之前季节中发生的抽样方差，实验村庄的数量正在被缩减，以便将村庄数量保持在一年中马哈季节3,000个和亚拉季节2,000个的范围内。此类限制的其他原因与实际方面有关，如调查成本和可用于执行作物收割的人数。

在每个选定的村庄进行两次作物收割实验。目前，样本村庄和地块是随机选择的。然而，在1980年之前，村庄和地块的选择都是随机进行的，选择概率与上一季种植的面积成正比，并使用替换方法。由于该程序相对繁琐且耗时，因此被目前的系统所取代，即两个阶段都是随机选择。样本村庄在总部选择，而地块的选择在各区进行。

非抽样误差的控制：为了确保实验结果的准确性，1/5的选定村庄将由来自区的执行官员/区负责人监督，例如DS/GA、区秘书、农业主任/副主任、农业专员，以及与区附设的DCS的高级职员。他们将通过访问样本村庄进行现场检查。

数据收集方式
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面对面 [f2f]

研究工具
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问卷为C.C.3表格，用僧加罗语/英语和泰米尔语/英语印刷。它分为三个部分。

第一部分关于地理和水稻田地块信息。

第二部分包括土地制度、土地准备方法、种子品种、播种方法、施肥、除草、杀虫剂、杀菌剂、对作物的不利影响。

第三部分收集产量信息。

在问卷中，上述信息为调查所选的两个地块记录。相同的C.C.3表格用于收集亚拉和马哈季节的数据。马哈季节在“东北季风”期间从9月到次年的4月。亚拉季节在5月至8月底有效。

抽样误差估计
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计算给定层的平均产量和方差的公式可在外部资源部分找到。