Portal de Periódicos da CAPES

Computer Programs That Calculate Manure Application Rates

1997; Wiley; Volume: 10; Issue: 1 Linguagem: Inglês

10.2134/jpa1997.0058

2689-4114

R.B. Thompson, D. Morse, K. A. Kelling, L. E. Lanyon,

Agriculture Sustainability and Environmental Impact

Decision support systems (DSSs) operated on personal computers are a convenient means to calculate application rates of livestock manures that meet crop nutrient requirements and avoid excessive nutrient applications. Twelve DSSs that can be used to calculate application rates of dairy manure are described and compared. The major functions of the programs, their input data requirements, and their software and hardware requirements are described. The major functional differences between the programs, their nutrient availability assumptions, and user-friendliness are discussed. The programs examined differ considerably in the number of functions they perform. The simplest programs estimate manure application rates for one field at a time. The more complex programs perform additional functions such as estimating the quantity of manure, calculating application rates for multiple fields, automatically allocating the estimated amount of manure to those fields, and calibrating manure spreaders. All of the programs use the same basic procedure to calculate manure application rates. This is essentially: (i) crop nutrient requirements are estimated, (ii) manure nutrient (N, P, and K) content is entered by the user or estimated by the program, (iii) availability factors are applied to the manure nutrients, (iv) the rate of manure to supply available nutrients to meet crop requirements is calculated, and (v) rates of any supplementary commercial fertilizer are calculated. The programs are typically developed for particular agricultural regions. Four of the programs examined have regional adaptability, achieved by enabling the user to directly enter or to modify factors used in calculating crop nutrient requirements and manure nutrient availability. DSSs have considerable promise in assisting with the many calculations required to determine manure application rates that meet crop nutrient requirements and minimize the risk of environmental pollution. The Issue The nutrient content of collected livestock manure applied to agricultural land is often discounted in farm nutrient management decisions. More effective use of manure nutrients can reduce the risk of associated environmental pollution and may also reduce the purchase of commercial fertilizer. Specialized software programs operated on personal computers are a convenient means to calculate manure application rates that meet crop nutrient requirements and avoid excessive applications of nutrients. Software programs that assist in technical decisionmaking are known as Decision Support Systems (DSSs). This study examined DSSs that can assist in calculating manure application rates. The objectives were to provide information to (i) assist potential users of such programs in selecting the programs most appropriate to their requirements, (ii) inform interested regulatory bodies of the capabilities and limitations of the programs, and (iii) assist developers of future programs to identify desirable features. Current Approaches The calculation of manure application rates involves lengthy manual calculations and the consultation of reference information such as the availability factors for manure nutrients. These calculations are seldom done since manure application rates are rarely determined on the basis of meeting crop nutrient requirements. Commonly, livestock farmers are mostly concerned with emptying manure storage units. This is normally done in accordance with “good agricultural practice” to avoid obvious forms of pollution. However, the systematic use of manure nutrients is not currently common farming practice. Study Description Twelve DSSs that can be used to calculate dairy manure application rates were selected. The major functions of these programs, their input data requirements, and their software and hardware requirements were described. The major differences between the programs, their nutrient availability assumptions, and user-friendliness were evaluated. The adaptability of the programs to regions different from those for which they were originally developed was assessed. Applied Questions What computer equipment and skills are required? The twelve programs operate on IBM® compatible personal computers. Eleven work satisfactorily on 386 computers and use Microsoft (MS) DOS® one also requires a spreadsheet program. All but the last can be started directly from the MS Windows v3.1® Program Manager screen. One program requires a 486 or Pentium computer and works with MS Windows v3.1® or Windows 950. The programs require only a working familiarity with computers. A good knowledge of agronomy is helpful when using the recommendations from the programs. How do these computer programs calculate manure application rates? All of the DSSs use the same basic procedure. Most estimate crop nutrient (N, P, and K) requirements; in some, these must be entered by the user. The manure nutrient content is entered, and the program applies nutrient availability factors. Availability factors consider manure characteristics and application method. The rate of manure application to supply available nutrients to meet the crop requirements is then calculated. Supplementary commercial fertilizer, to ensure all crop nutrient requirements are met, is also calculated. What are the advantages of using DSSs to calculate manure application rates? Compared with manual calculation, DSSs considerably reduce the effort and time involved in calculating manure application rates to meet crop nutrient requirements. Following data entry, multiple calculations are made very quickly. Time is not spent obtaining reference information (e.g., nutrient availability factors). Saving input data enables different management options to be rapidly examined. How do the programs differ? The 12 DSSs vary considerably in complexity. The simplest determine manure application rates for a single field. The more complex have multiple functions such as automatically allocating the quantity of stored manure to multiple fields, and estimating the number of spreader loads and the financial value of the manure applications. Some of the DSSs take a strict approach to nutrient management, requiring soil test data to estimate crop nutrient requirements, others allow the user to enter the crop requirements. Can the programs be used in different regions? The DSSs examined were typically developed for one region. For most of the programs, numerous aspects are region specific: cropping options, estimation of crop nutrient requirements, manure application methods, nutrient availability factors, etc. Some programs have provision for these factors to be altered to enable regional adaptation. Those that do not are restricted to the region for which they were produced. Recommendations Decision Support Systems are a very promising method for assisting with the systematic use of the available nutrient contents of livestock manure. Programs must be suitable for the regions in which they are to be used. Extension staff and leading farmers should be encouraged to use these programs, given that suitable support is available. Research is required to ensure that nutrient availability factors are as accurate as possible.