Utility of proximal plant sensors to support nitrogen fertilization in Chrysanthemum

Chrysanthemum morifolium Ramat. is a commonly grown ornamental worldwide. A proper timing of nitrogen (N) supply is essential for a qualitative crop and the return on investment for growers. Sub-optimal nitrogen nutrition negatively influences the commercial plant quality, while supra-optimal N has an environmental impact due to nitrate leaching. Therefore, (a) reliable indicator(s) of plant nitrogen status is/are needed. Two field-grown potted Chrysanthemum cultivars, 'Maya' and 'Orlando' were studied for three consecutive years (2016-2018). Three different N treatments were applied in order to obtain a variation in N content. Plant quality measurements consisted of plant height, diameter, leaf mass per area (2017 and 2018 only), biomass and foliar and plant N content analysis. Optical measurements were performed with a SPAD sensor (2016 and 2017) and a Dualex Scientific sensor (2017 and 2018) on leaf level and with a GreenSeeker NDVI meter on canopy level. Biomass, height and diameter tended to be smaller in the minimal fertilizer treatments. Leaf mass per area did influence the relation between N and chlorophyll measured with SPAD and Dualex. Epidermal polyphenolics measured with Dualex correlated better with foliar nitrogen than non-destructive chlorophyll measurements and the nitrogen balance index. Since abaxial epidermal polyphenolics were highly correlated with foliar nitrogen and convenient to measure in-field, we propose this measurement for decision support in Chrysanthemum fertilization. Because of cultivar and sometimes year-to-year variability, reference plots can be of help for growers and advisors. NDVI was found to be more susceptible for yearly variation, but very high correlation with several quality parameters and convenience in use make this vegetation index useful for detecting the extent of spatial quality variability and thus support site dependent N requirements to reach the desired plant diameter at the end of the growing season

Application of proximal optical sensors to fine-tune nitrogen fertilization : opportunities for woody ornamentals

Today, high amounts of residual nitrogen are regularly being reported in the open field production of hardy nursery stock. In some cases, excessive fertilizers or side-dressings are applied when circumstances are not favorable for uptake. Aquatic as well as terrestrial ecosystems are sensitive to enrichment with nutrients, but growers also benefit when losses are avoided. In this study, the potential of proximal optical sensors to optimize nitrogen fertilization was investigated in four woody species: Acer pseudoplatanus L., Ligustrum ovalifolium Hassk., Prunus laurocerasus 'Rotundifolia' L. and Tilia cordata Mill. For three consecutive growing seasons, plants were grown under three different fertilization levels to generate different nitrogen contents. Plant growth and nitrogen uptake were monitored regularly and combined with sensor measurements including Soil Plant Analysis Development (SPAD), Dualex and GreenSeeker. Here, we show that optical sensors at the leaf level have good potential for assisting growers in the sustainable management of their nursery fields, especially if leaf mass per area is included. Nevertheless, care should be taken when plants with different leaf characteristics (e.g., wax-layer, color, and leaf thickness) are measured. When all measuring years were considered, high correlations (R-2 >= 0.80) were found between area-based foliar nitrogen content and its non-destructive proxy (i.e., chlorophyll)measured by Dualex or SPAD. Based on our results, we recommend a relative rather than absolute approach at the nursery level, as the number of species and cultivars produced is very diverse. Hence, knowledge of absolute threshold values is scarce. In this relative approach, a saturation index was calculated based on the sensor measurements of plants grown in a reference plot with an ample nitrogen supply

Experience with fertilizer expert systems for balanced fertilizer recommendations

To evaluate soil fertility and to calculate fertilizer recommendations for different soil types and crop rotations, two expert systems were developed and are being used in Belgium and the Northern part of France. The BEMEX expert system (BEMEX, coming from BEMEstingsEXpertsysteem, Dutch for fertilization expert system) calculates field specific fertilizer recommendations for macronutrients and liming recommendations for crop rotations with arable crops and vegetable crops and for grasslands. The N-INDEX method is a field specific advice-system for N-fertilizer recommendation for most arable and vegetable crops. The knowledge base of BEMEX as well as of N-INDEX contains empirical and theoretical knowledge, The required information to run the expert systems consists of measurements of the chemical soil fertility on soil samples on the one hand and of information concerning the parcel and the crop on the other hand. The final output of the expert system is a two-to-five page bulletin, with the results of soil analysis and the fertilizer and liming recommendations. This bulletin is sent to the farmer. Additionally, an impressive database with soil fertility data is gathered annually. As a consequence presentation models such as choroplets, pie charts, etc. are useful tools to describe soil fertility on the basis of numerous soil analyses. Both the personalized advice bulletins and the general presentation models are the interface between the expert and the user of the expert system, which is commonly the farmer himself or extension staff members. BEMEX and N-INDEX are useful tools for operational decision support on the subject of liming and fertilization.status: publishe

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Diss. lic. informatic

Garden management and soil fertility in Flemish domestic gardes

Collectively domestic gardens form an important landscape component, but environmental and land use policies tend to ignore domestic gardens. This paper investigates nutrient cycling in domestic gardens: fertilizer and soil conditioner use, composting, removal of grass clippings and the soil fertility states in the case of Flanders (the northern part of Belgium). Data was assembled from an internet survey about garden management and a database on soil fertility of domestic gardens. The combined analysis of these data reveals new insight in the link between garden management and the chemical condition in gardens (in terms of soil carbon content, pH and phosphate). Flemish gardeners used 0.07kg fertilizer and removed 2.3l grass clippings per m2 garden in 2007. Meanwhile, garden soils appear to have a higher pH and phosphorus content and lawns a lower carbon content than optimal agronomic standards. These insights show that gardens are a dynamic socio-ecological system with considerable nutrient flows from and to the household and the environment, indicating the need for more detailed and systematic environmental monitoring. This way, domestic gardens can be compared to agriculture, horticulture and other land use types. This and complementary research helps to complete insights in the dynamics across complex rural and urban landscapes. Future research should take into account, among other things, prevailing practices and habits of garden owners. © 2013 Elsevier B.V.status: publishe

The ISO-group concept as a tool for optimizing crop production at farm level

Yield and quality of agricultural crops are influenced by a large number of factors. Some of these are inherent to the field on which the crop is grown. They define the intrinsic capacity of a field and cannot or hardly be modified by man. The so-called management factors can be adjusted or influenced as required for optimum production. In the present concept, the maximum attainable yield is considered to be the highest observed yield within a group of fields with comparable intrinsic value, further called iso-group. The grouping (positioning step) is based on a set of permanent characteristics determined mainly by physical environment. Each unique combination of these characteristics, established by using a GIS-tool, gives rise to a new iso-group. After appointing each field to an iso-group, a ranking can be made within each group based on yield or quality. During the diagnosis step the contribution of each management variable to the observed variation in yield and/or quality within an iso-group, is determined. In this way the most relevant variables are selected and the relationship with the yield and/or quality is establised. Based on these relationships specific measures can be suggested to improve the yield and/or quality of the crop on a specific field (advising step). By applying these recommendations the farmer is expected to obtain yields that approximate te maximum intrinsic capacity of his plot.status: publishe

Modeling the productivity of agricultural crops in response to water and nitrogen availability

Interception of photosynthetical active radiation, water and nitrogen uptake are the most important processes governing crop growth and production. Each of these processes is handled in a general way, and based on experimental evidence the main features are depicted. Light interception by a crop canopy determines the potential growth rate, provided the water and nitrogen uptake rates are optimal. Reasons for yield reductions in response to water and nitrogen shortage are clarified. During the growing period, the availability of growth factors can vary widely.Dynamic simulation models are a valuable tool in studying the quantitative aspects of crop growth processes. The way in which potential growth processes are modeled is presented. As water and nitrogen shortages put restrictions on the potential growth, these effects are modeled by their impact on relevant physiological processes. Finally, attention is paid to the practical use of simulation models with respect to agricultural crop productivity.status: publishe

Impact of long term compost amendments on soil fertility, soil organic matter distribution and nitrogen mineralization

Soil organic matter is a major carbon pool and can play a significant role in carbon mitigation measures. It is also a crucial factor for several soil physical properties and a major nutrient source for crops. To obtain an understanding of the changes that occur in the soil following long term annual compost application, the Soil Service of Belgium started a long term field trial in Boutersem, Belgium in 1997. Here 12 different treatments (fallow, unfertilized, mineral fertilized and 9 compost treatments differing in intensity from 15 to 45 t/ha and in frequency from annual to tri-annual) were implemented in 4 repetitions. All compost amended treatments substituted (part) of the mineral nutrient requirements of the crop and had a positive influence on soil chemical and physical parameters. The continued application of compost also has important effects on the amount, distribution and stability of the soil organic matter. To quantify this, soil samples from 5 treatments were divided into 7 fractions differing in physical and biochemical protection levels of the associated SOM. Not only did the total amount of carbon in the amended soils increase significantly over the course of the experiment, it also increased specifically in the less protected SOM fractions. These results were combined with a 400 day long incubation experiment to investigate the influence of long term compost fertilization, causing an altered SOM distribution, on the soil respiration and nitrogen mineralization.status: publishe