Submitted to: International Conference on Precision Agriculture Abstracts & Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/23/1996
Publication Date: N/A
Citation: Interpretive Summary: Growing conditions are not uniform across a 120 acre potato field. Some areas of the field are very sandy, while others are more loamy. There are high spots that drain well and might be too dry, and low spots that are too wet. The amount of various plant nutrients left in the soil will depend on factors such as drainage and how well the previous crop grew in any particular spot. Despite these differences, we add fertilizer, water, and other management inputs in a uniform manner. Each plant in the field is an integrator of its growing conditions, resulting in a product with a certain weight and quality. Comparing the yield with the growing conditions for each plant would help optimize management inputs, but this is not feasible for whole fields. Traditionally, farmers know the yield for the field, and use this to estimate the average per-acre yield. This information is not sufficient to help us understand or manage the variability in the field. A Apotato yield monitor and a differential global positioning satellite syste were used to record yield and exact location every three seconds during the normal harvest of five commercial potato fields. From this information, we determined there was a great deal of yield variability in these fields. Yields are reported as percentages of the five-field-average to protect the privacy of the grower. Yield in a 20'x 20' area ranged from 1% to 325% of average in the most uniform field, and from 1% to 685% of average in the most variable field. Whole-field averages ranged only from 89% to 112% of the five-field-average. It is apparent that much information on yield variability is lost by using whole field averages. Identifying and understanding yield variability is an important step to managing field and pest variability to obtain uniform yields.
Technical Abstract: Precision management of center pivot irrigated fields requires a knowledge of spatial variation within the field. Yield represents the integration of a multitude of processes taking place in the field, and is a reasonable place to begin to identify significant areas of variability. We mapped potato yields in five commercial center pivot fields (240 ha total size) in nsouth central Washington using the HM-500 yield monitor developed by HarvestMaster, Inc. A pair of spread spectrum radio modems was used to transmit real-time yield data from the harvester to the mobile office. This allowed a real-time display of the raw yield data on the computer in the mobile office, permitting problems to be immediately detected without having to have an observer on the harvester. Yield and GPS location were recorded every three seconds. Substantial spatial variability of potato yields, both within and between fields was observed. Yields are reported as percentages of the five-field-average to protect the privacy of the grower. Yield in a 20'x 20' area ranged from 1% to 325% of average in the most uniform field, and from 1% to 685% of average, in the most variable field. Whole-field averages ranged only from 89%, with a CV of 30.26, to 112%, with a CV of 34.41, of the five-field-average. Much of the site- specific information on yield variability is lost by using whole field averages. Yield monitors and GPS allow much of this variability to be identified and documented in yield maps. The yield maps will be used to identify high and low yielding areas to focus further precision management research efforts. This is a first, important step to precision crop management.