Predicting of Field Working Days of Planting and Harvesting Operations for Sorghum Crops Damazeen Area (Sudan)

The most uncontrollable variable in agricultural operations is the number of proper working days in a cropping year. A method for determining the appropriate working days is to obtain a reasonable relationship based on the previous year’s temperature and rainfall. This method of probability distribution clarifies the appropriate dates for each key activity throughout a year. Field capacity and climate conditions are the main factors for determining the appropriate time for agricultural operations during the year. The required time for working with field machinery depends on the machine capacity and the number of appropriate working days. Each region of the country has its own climate pattern. Working days of the field is determined by two factors. First, the soil moisture content should not exceed the plasticity limit; second, the rainfall on that day should not be greater than 10 mm. The effect of other climate conditions such as freezing occurrence probability or snowing are not included in the analysis of soil working days (Witney 1988).

Adverse soil condition makes it difficult or impossible to perform some field operations. Suitable days, being related to random weather related events, are thus also random in nature. Information about the probability distribution of suitable days during critical production periods would help farmers determine their optimal machinery complement and crop mix. Probability of a working day (PWD) is the fraction of workable days to all days in a work season, which often is used in management of agricultural mechanization. For example it is used to determine timeliness cost, optimum capacity of a machine and the required machine capacity (Saglam and Ibrahim, 2011 ). Accurate information on the number of suitable days for field operations is important in design, development, and selection of efficient machinery systems for crop production (Khan et al., 2011). In order to predict the amount of work that can be accomplished, the time available within the optimal period for the required operation must be known. The time available varies considerably from year to year as weather conditions vary. Selection of the optimal machinery set for long-term production on the farm depends upon accurate assessment of the days available for performing each field operation (Rotz and Harrigan, 2005). The most restrictive factor for harvesting operation is the soil moisture. Soil moisture content and the vagaries of weather are the two major factors which determine the amount of time available throughout the year for field operations (Witney, 1988).

In a poor season, little time may be available for performing one or several field operations under acceptable conditions. A favorable weather pattern and a friable soil, provide available or possible time within which the field work can be completed without working excessively long hours, or working in unsatisfactory conditions he weather interacts both with the soil to vary soil workability for tillage operations and with the crop to vary yield and moisture content at maturity for harvesting operations, whilst the influence of the weather on soil tractability affects all operations to a greater or lesser extent. The workability / trafficability of the soil is dependent on the soil moisture content which can be evaluated from soil and weather variables (Witney, 1988).Provided that all the relevant operating conditions can be specified for the soil and the crop, suitable workdays can be identified. As a preliminary stage, commonly accepted operational times are used to provide workday data for strategic planning purposes. It is common practice with respect to farm operations within the savannah agro-ecological zone of Nigeria to find farmers using their intuition and traditional knowledge acquired from their mentors, using unconventional methods in estimating suitable field workdays rather than the scientific methods which are more reliable and dependable. The scientific methods are more useful in estimating suitable field workdays for better farm yield or benefits. Thus, it is the aim of this paper to collated useful weather, soil moisture and soil conditions (soil liquid and plastic limits) parameters using soil moisture budgets empirical methods which was then programmed using Virtual Basic 2008 to segregate the suitable and non-suitable workdays for planting and harvesting operations on a mechanized maize farm. Available time for any field operation is a function of a suitable workday. Cooper et al., (1997) stated that the time available for completion of field work depends on such factors as weather, soil characteristics, hours worked per day, number of days allowed for completion of field operations, scheduling efficiency, machine reliability and field efficiency. Principally, soil moisture budget.