J. Bries

Application of Humic Substances Results in Consistent Increases in Crop Yield and Nutrient Uptake

ABSTRACT The effect of humic substances on yield and nutrient uptake of grass, maize, potato and spinach was investigated in six field experiments and two pot experiments in a high input cropping system. The humic substances originating from leonardite formations in Canada were applied as liquid solution to the soil (Humifirst liquid) or as a solid incorporated in mineral fertilizers (Humifirst incorporated). Formal meta-analysis of the results of all executed experiments showed that the application of humic substances had an overall positive effect on dry matter yield of the crops and this effect was statistically significant for Humifirst incorporated. In the case of permanent grassland, humic substances promoted mainly the production of the first grass cut, which has the highest grass quality among all cuts during the growing season. Tuber production on the potato field trial showed a high response on the application of humic substances. Total potato yield increased with 13 and 17% for Humifirst liquid and Humifirst incorporated, respectively. The effect of humic substances on maize yield was limited, probably due to the rather high nutrient status of both soils. Finally, the formal meta-analysis showed a consequent increase in nitrogen and phosphorus uptake of all studied crops as well. The effect on potassium and magnesium uptake was also mainly positive, while sodium and calcium uptake were not affected in most of the experiments.

Experience with fertilizer expert systems for balanced fertilizer recommendations

Abstract 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 resul...

Evaluation of fall residual nitrogen influenced by soil chemical characteristics and crop history in flanders (Belgium)

Abstract In the framework of the “Directive concerning the protection of waters against pollution caused by nitrate from agricultural resources (91/676/EEC),” losses of nitrate nitrogen to groundwater and surface water have to be limited. In the moderate climate regions of western Europe, drainage losses mainly occur during wintertime. The residual nitrate nitrogen in the soil profile after the harvest in autumn is considered as the main determinant of nitrate losses. In Flanders, a preliminary limit value of 90 kg NO3‐N ha−1 up to a soil depth of 0.90 m between 1 October and 15 November is proposed. During this period in 2001, the Soil Service of Belgium sampled >18,000 fields. From these results, some interesting conclusions can be drawn. As expected, differences in residual nitrate after harvest are highly influenced by the crop, soil type, and carbon content of the soil. The percentage of fields with a residual nitrate nitrogen content below the target value of 90 kg N ha−1 differed from 39% to 86%, because of the influence of the crop grown on the parcel. On an average, a high nitrate value was found after early harvested crops (cereals, flax [Linum L.]) and after crops with high protein content due to plant residues remaining on the field after harvest (peas [Pisum sativum L.] and beans [Phaseolus vulgaris L.]). Soil type was also important because, only 42% of the fields with clay soils were below 90 kg NO3‐N ha−1, and in sandy soils this figure was 75%. This is probably partly caused by leaching in the period after harvest until sampling. A very important factor was the carbon content of the soil. Because of a higher mineralization rate in the period after harvest, only 38% of the fields characterized by a high C content were found with a nitrate content below 90 kg NO3‐N ha−1 in contrast to 78% of the fields with a very low C content. Finally, because of the influence of the climatological conditions on nitrogen mineralization and nitrate leaching, the changing weather conditions during the 6‐wk‐long sampling period influenced the amount of residual nitrogen in the soil.

Experience with a nitrogen-index expert-system - a powerful tool in nitrogen recommendation

Abstract The expert system nitrogen (N)‐index calculates N fertilizer recommendations for arable crops in temperate regions. The knowledge base of N‐index leans on different fundamentals, such as the measurement of the mineral N stock in soil in spring, the calculation of the evolution of the mineral N content in time and depth in the soil profile as well as the crop response to N fertilizer rates. The calculations with the empirical and theoretical founded knowledge base results in a N‐index value, which is subdivided into different values each representing a major point of vue to know the N availability for the growing crop. Since the introduction of the N‐index expert system in Belgium and the northern part of France in 1979, many crops were added to the knowledge base. The number of samples and correlated analysis data increased, making it possible to review accurately the mineral N stock in the soil after the winter period as a function of many factors, e.g. previous crop and organic fertilizer appli...