Crop Estimating Survey on Paddy (Yala) - 1983 - 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 in 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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Special remarks - effective from 2005/2006 Maha Season

In order to perform these steps, Crop Cutting Officers should get the fullest co-operation from selected farmers. According to the available information, the whole process of conducting such an experiment takes around three hours. Also, all steps are being performed manually in many occasions. It is obvious that the crop cutting is a laborious procedure at present. Considering the volume of work and practical difficulties which could affect negatively, it is a must to introduce an updated method in order to maintain the quality of data. Some of the suggestions to overcome this burden are as follows.

(1) Reduce the volume and time of involvement of the officers
(2) Introduce modern equipment to thresh the grain or assess the paddy yield of the plot.
(3) Replace the current methodology with an alternative survey procedure.

As an initial step, the Agriculture Division of DCS in line with above suggestion noted in (1) a pilot survey has been conducted in Kegalle District in the 2005/06 Maha season. This was extended to Matara and Kurunegala Districts during the Maha 2007/08, by reducing the experimental plot size to half of that of the standard plot which is used at present. Now, the Agriculture Division is statistically testing the results of the pilot survey against the results of the standard survey conducted hitherto. If there is no significant difference between these two, the new plot size would be introduced in the near future.
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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, the actual length and breadth of these plots should be deducted.

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. The whole procedure in conducting the experiment is stated in detail in the manual of Crop Cutting Experiments prepared by the Agriculture Division. 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.

Estimation of Average Yield of Paddy
Average yield of paddy per acre/hectare by mode of irrigation and by District is being estimated through an objective survey which is popularly known as crop cutting survey on paddy. This has been initiated in 1950 and the methodology introduced by Dr. Koshal, Statistician of FAO (an Indian expert) under the assistance of FAO. From time to time some modifications have been introduced and the procedure is still in operation to estimate the paddy production in each season.

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 March 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，俗称‘割谷调查’，始于1950年。该调查在马哈和亚拉季节进行，旨在估算水稻的平均产量和各地区的产量。在马哈季节，大约进行6,000次实验，在亚拉季节大约进行4,000次实验，它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在诸多方面受益，例如及时进口国家额外大米需求量的决策、评估提升水稻平均产量所实施的推广项目、大米定价政策、从一地调动库存至另一地等。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。
在各个地区附属的现场工作人员被委托负责各种数据收集活动，其中，割谷调查的数据收集方法与其他调查不同。该调查采用一种客观方法；因此，割谷官员应亲自在现场进行实验。根据标准程序，割谷官员必须访问选定的稻田，并应遵循一系列步骤，例如：划定相当于16' ½'' X 16' 1/2"（一英亩一个 perch 的稻田）的指定地块，收割地块的作物， threshing 谷物，使用标准量杯测量谷物，最后通过规定的表格 CC3 报告结果。
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特别说明 - 自2005/2006年马哈季节起生效

为了执行这些步骤，割谷官员应从选定的农民那里获得全面合作。根据可用信息，整个实验过程大约需要三个小时。此外，在许多情况下，所有步骤都是手动执行的。显然，目前割谷是一项繁重的工作。考虑到工作量以及可能产生负面影响的实际困难，必须引入一种更新的方法，以保持数据的质量。以下是一些克服这一负担的建议。
(1) 减少官员的参与量和时间
(2) 引入现代设备来 threshing 谷物或评估地块的水稻产量。
(3) 用替代调查程序替换当前的方法。

作为第一步，农业部门的 DCS 与上述第(1)点建议一致，在2005/06马哈季节在凯加勒地区进行了试点调查。在2007/08马哈季节扩展到马塔拉和库鲁内加拉地区，将实验地块面积减半至目前使用的标准地块面积。现在，农业部门正在对试点调查的结果与迄今为止进行的标准调查的结果进行统计分析。如果没有显著差异，则将在不久的将来引入新的地块面积。
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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 - 在斯里兰卡，有两个与两个季风相关的主要栽培季节，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体季节，有效期为当年的9月至次年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。

主要灌溉工程被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。

降雨灌溉是指在缺乏永久性水塘或水库的情况下，栽培面积完全依赖降雨水的灌溉方式。

产量以公吨为单位报告。

每英亩或公顷的平均产量：通过割谷调查估计的每个面积单位的生产力指标（2.471英亩=1公顷，而1公顷等于10,000平方米）。平均产量以蒲式耳报告每英亩，以公斤报告每公顷。

平均产量以糙米（带壳的谷物，但不是米的形式）表示。

收获面积是指收获的总面积，不包括因不同原因受损的面积。

毛面积是指由统计员或受访者根据种子率估计的栽培范围报告的面积，而不是根据地籍调查报告的面积，而净面积是指扣除用于埂和脊的面积所形成的面积。

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年的产量是2004/05马哈季节和2005年亚拉季节的总和。

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" 的水稻地块，在梯田中使用较小的实验地块尺寸时，应扣除这些地块的实际长度和宽度。

总体
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调查覆盖了斯里兰卡所有水稻地块的随机样本。

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（即主要、次要和降雨灌溉）被视为子层。每个方案中用于割谷实验的村庄的选择数量基于以下比例。

上一年度播种面积

要选择的村庄数量

< 500 英亩

3

500 - <1000 英亩

5

1000 - < 5000 英亩

10

5000 - < 10,000 英亩

15

10,000 - < 15,000 英亩

20

15,000 - < 20,000 英亩

25

20,000 英亩及以上

30

尽管建议的设计是这样的，但考虑到上一季节出现的抽样方差，为了将村庄数量保持在一年中马哈季节3,000个村庄和亚拉季节2,000个村庄的范围内，正在减少要选择的实验村庄数量。这种限制的其他原因与调查的实际方面有关，如调查成本和可用于执行割谷的人数。

在每个选定的村庄进行两次割谷实验。实验的整个过程在农业部门准备的《割谷实验手册》中有详细说明。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，概率与上一相应季节的栽培面积成正比，并且是可替换的。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的。样本村庄在总部选择，而地块的选择在相应的地区进行。

非抽样误差的控制：为了确保实验结果的准确性，应监督1/5的选定村庄的执行官员/地区负责人，这些官员/地区负责人是从地区中确定的，例如DS/GA、分区秘书、农业局长/副局长、农业发展副专员，以及附属于地区的DCS高级工作人员。他们将通过访问样本村庄进行现场检查。

估算水稻的平均产量

通过一种客观调查估算灌溉方式和地区的水稻每英亩/公顷的平均产量，这种调查通常被称为水稻割谷调查。该调查始于1950年，由FAO统计学家Koshal博士（一位印度专家）在FAO的协助下引入。随着时间的推移，引入了一些修改，该方法仍在运行，以估算每个季节的水稻产量。

数据收集方式
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面对面 [f2f]

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

第一部分是关于地理和水稻地块信息。

第二部分包括土地制度、土地准备方法、种子品种、播种方法、肥料应用、除草、杀虫剂、杀菌剂、作物不利影响。

第三部分收集产量信息。

在问卷中，为调查选择的两个地块记录了上述信息。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月至次年3月。亚拉季节在5月至8月底有效。

抽样误差估计
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在“外部资源部分”中提供了计算给定层平均产量和方差所需公式的公式。