Hermann J. Heege

Precision in Guidance of Farm Machinery

Georeferencing by GNSS has opened up possibilities for precise guidance of farm machinery along virtual lines in the fields. The guidance takes place either manually with the help of lightbar indications or in an automatic way. The driver concentrates on supervising the machinery.

Sensing of Natural Soil Properties

Site-specific sensing of varying natural soil properties is a prerequisite for an adequate control of many field operations.

Site-Specific Sowing

Site-specific control of the seed-density can rely on maps of soil texture. The seed-density should rise from sand to silt and loam and fall again towards clay. In this way either the yields can be increased or seeds can be saved.

Site-Specific Fertilizing

Fertilisation aims at providing soils with nutrients for high crop yields without adversely affecting the environment. Since in most cases the properties of soils as well as of crops vary within individual fields, site-specific fertilization is needed. The challenge is to find sensing methods that provide suitable signals for the site-specific control of fertilizer application. Feasible approaches to meet this challenge are based on recording the yield of previous crops and the nutrient removal derived from it electrochemical indication of nutrients in soils by ion-selective electrodes sensing the nutrients either in soils or in crops via optical reflectance.

Site-Specific Soil Cultivation

Site-specific soil cultivation has several objectives. In primary cultivation, the main objective is the control of the working depth. Signals for this control can be derived from the clay content, the organic matter content, the hydromorphic properties and the slope of the soil. An algorithm can combine these signals to control the working depth. The soil resistance to penetration is a suitable control signal for sensing hardpans below the topsoil, but not for the working depth within the topsoil, since it depends mostly on the water content.

Site-Specific Sensing for Fungicide Spraying

Especially in humid moderate climates, high yields require the application of fungicides. Its site-specific application based on the biomass of crops is state of the art. Yet this technique does not take into account that fungal infections in most cases start and spread out from small, initial spots within a field. So a sensing technique to detect these initially small infected spots would be of great importance for saving fungicides, for reducing damage to crops as well as to the environment and for allowing higher driving speeds in uninfected areas. Reflectance indices of visible and near-infrared light as well as indices of fluorescent light are candidates for detecting these spots.

Heterogeneity in Fields: Basics of Analyses

Sustainable and economical farming needs precise adaptation to the varying soil- and plant properties within fields. Consequently, farming operations have to be adjusted to this in a site-specific way.

Fusions, Overlays and Management Zones

Site-specific farming can be based on various signals about soil- and crop properties. And some farming operations might need a control that relies simultaneously on several properties. However, the control of an individual farming operation requires singular and unambiguous site-specific signals. Hence, information about soil- and crop properties must be merged. Means to achieve this are sensor-fusion, map-overlay and management zones.

Sensing of Crop Properties

Sensing of crops by visible and infrared reflectance allows estimating the chlorophyll concentration within leaves as well as the leaf-area-index. The product of the chlorophyll concentration within leaves and the leaf-area-index supplies the chlorophyll content per unit field area. Recording this criterion repeatedly during the season provides reliable estimates of the site-specific yield potential as based on past growing conditions.

Summary and Perspectives

Future farming has to provide high yields in order to feed the growing world population, but should do this with an environmental impact that is sustainable. With the limited resources of the planet earth, this dual challenge can only be met by precise adaptation to the locally varying conditions. And since the field boundaries by no means are precise environmental borders, this necessitates site-specific farming within single fields.