COPdate

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Introduction

In order to correctly simulate the crop growth reliable, realistic sowing dates and cycle length are fundamental. Moreover in tropical and sub-tropical regions like South-China two or especially tree cropping cycles are possible. In these regions the knowledge of real crop rotation and the suitable crop calendar (e.g. for early and double season late rice) is fundamental for an accurate yield forecast. One possible option to find such data is the usage of COPdate (Climatically Optimal Planting date, Savin et al. 2007). This application finds sowing dates for a specific combination of crop, grid and year, according to expert rules. In the original version, the package was also used to estimate initial soil water. However, in the current system this functionality is disables. Initial soil water is estimated by other external scripts.

Architecture

The application is implemented as an oracle package. By running the package for all historical years, the earliest and latest optimal sowing date can be found, defining the a sowing window. By processing a specific year, the optimal sowing date for that year inside the sowing window is found. To be able to run the package in parallel, it is connected to a tasks administration system that should be configured before searching for sowing dates.

Configuration

To initialize tasks for COPdate, the INIT_TASKS procedure is used. Five or six arguments are required:

To initialize a single year:

  • task (= cop-sd)
  • initial status (= pending)
  • crop
  • year
  • regime (winter or spring)

To initialize multiple years:

  • task (= cop-sd)
  • initial status (= pending)
  • crop
  • start year
  • end year
  • regime (winter or spring)

If start- and end year are NULL then all the years in the crop_calendar will be initialized for the crop and grid(s). If start- or end year is NOT NULL, then this value will be used as start- resp. end year of the range of years; the other value will be derived from the crop_calendar. If both start- and end year are NOT NULL these values will be used as start- resp. end year of the range of years; only this range will be processed. The start- and end year will be included in the range to be processed. The above procedure fills the TASK_LIST table in the assisting schema (e.g. RUKMAN) which transfers the tasks via views to the various TASKLIST views in the main schema (e.g. CGMS14RUK).

Rule parameter values can be configured per crop and regime in table COP_CROP_REGIMES.

Planting date Rules

Region specific expert rules have been defined which estimate climatically optimal sowing dates for different crops. In the original COPdate packages, the rules were elaborated from agronomical practices in the former Soviet Union, Central Asian and non European Mediterranean regions covering 30 countries among major producers such as Russia, Ukraine, Kazakhstan, and Egypt. During application of the package, some rules for finding sowing windows were adjusted to better match observed sowing dates. Crops are classified basically in 2 groups and subdivided further. No sowing date rules are developed for the second group.

sowing depending on precipitation and/or air temperature

  • winter crops
  • spring sown crops
  • autumn sown crops

sowing independent from meteorological circumstances

  • in chain sowing
  • others

Short names winter, autumn and spring for the subgroups of the first group are indicated as regimes.

Winter crops

The rules apply for winter crops such as winter wheat, winter barley and winter rapeseed.

The first step consists of determining the sowing window from at least 15 years of meteo data. For each year the day is selected on which the TSUM threshold of 500 ºC is crossed, starting from December 31st going backwards, only summing degrees above 3 ºC (TBASE) and not going back further than September 1st. The end of the sowing window is the latest day found over all years. The start of the sowing window is 1 month before the end. The crop and grid specific sowing windows are stored in table COP_WINDOWS.

In the second step, the year specific sowing date inside the sowing window is found by the following rules, starting at the beginning of the sowing window.

  1. Day check: If day is the last day of the sowing window, sowing takes place, else go to next step
  2. Cold check: If average temperature over the past 10 days > 14 ºC, go to the next day and return to step 1, else go to next step
  3. Workability: If within the previous 3 days precipitation > 3 mm, go to the next day and return to step 1, else go to next step
  4. Sufficient water: If precipitation sum over past 20 days < 10 mm, go to the next day and return to step 1, else sowing takes place

In the current operational set-up, the workability and sufficient water rules are not applied and the cold check threshold was lowered from 17 to 14 ºC. The crop, year and grid specific sowing date is written in table CROP_CALENDARS. If meteo data are incomplete, the tasks is exited with an error.

Spring sown crops

The rules apply for summer crops such as spring sown wheat, spring sown barley, spring sown rapeseed, maize, millet, sorghum, sugar beet, sugar cane, soy bean, sunflower, potatowinter, potato-spring, potato-summer and rice.

First a preliminary sowing window is determined by a four month window around the long term average sowing date given by the FAO (stored in table COP_CROP_GRID_REGIMES). For each climatic grid cell the sowing date is estimated for each of the last 15 years based on the following rules, starting at the first day of the preliminary sowing window. There is no rule for checking sufficient water since it is assumed that the crops in this group are irrigated.

  1. Day check: if day is the last day of the preliminary sowing window, sowing takes place, else go to next step
  2. Temperature check: if average temperature over the past 10 days < a crop specific threshold, go to the next day and return to step 1, else go to next step
  3. Crop check: if Rice, sowing takes place, else go to next step
  4. Workability: If within the previous 3 days precipitation > 3 mm, go to the next day and return to step 1, else sowing takes place

In the current operational set-up, the workability rule is not applied. The final sowing window is defined by the earliest and latest sowing date found over the past 15 years. The crop and grid specific sowing windows are stored in table COP_WINDOWS.

In the second step, the final year specific sowing date inside the sowing window is found by following above rules again, now starting at the beginning of the final sowing window, and not going further that the last day of the final sowing window. This way, when running the COPdate for an operational current year, only the final sowing window has to be checked, and not the full FAO window. Again the workability rule is not applied in the current operational set-up. The crop, year and grid specific sowing date is written in table CROP_CALENDARS. If meteo data are incomplete, the tasks is exited with an error.

Autumn sown crops

The rules apply for autumn sown summer crops such as wheat, barley, rapeseed and potato-fall with continued growth in winter in regions without frost (in Northern Africa). These crops have in common that they require cool conditions during sowing (below 17 ºC).

First a preliminary sowing window is determined by a four month window around the long term average sowing date given by the FAO (stored in table COP_CROP_GRID_REGIMES). For each climatic grid cell the sowing date is estimated for each of the last 15 years based on the following rules, starting at the first day of the preliminary sowing window.

  1. Day check: if day is the last day of the preliminary sowing window, sowing takes place, else go to next step
  2. Cold check: if average temperature over the past 10 days > 17 ºC, go to the next day and return to step 1, else go to next step
  3. Sufficient water: if the sum of the difference between rainfall and ETA over the past 10 days < 0, go to next day and return to step 1, else sowing takes place

In the current operational set-up, the sufficient water rule is not applied. The final sowing window is defined by the earliest and latest sowing date found over the past 15 years. The crop and grid specific sowing windows are stored in table COP_WINDOWS.

In the second step, the final year specific sowing date inside the sowing window is found by following above rules again, now starting at the beginning of the final sowing window, and not going further that the last day of the final sowing window. This way, when running the COPdate for an operational current year, only the final sowing window has to be checked, and not the full FAO window. Again the sufficient water rule is not applied in the current operational set-up. The crop, year and grid specific sowing date is written in table CROP_CALENDARS. If meteo data are incomplete, the tasks is exited with an error.

Application of the package

To find optimal planting dates, the functions PROCESS_COP_OSD_BLK for a single year, or PROCESS_COP_SD_ALLYEARS_BLK for multiple years are called. These procedures pick up tasks with phase Pending and of a certain age. They are processed one by one at a time. When picking up a task, its phase is updated to In progress. In case of an error, the phase is updated to Error. When a sowing date is found, the phase is updated to Resulted and the found sowing date is updated in the CROP_CALENDARS table. When no sowing date is found, the phase is update to No result and a new tasks is created with phase Pending. When no more tasks of a certain age and with phase Pending are found, the processing is aborted.

The use and administration of the tasks allows that the COPdate can be called in parallel since only pending tasks of a certain age are processed (thus ignoring just newly created tasks).