PLACEMENT OF SOLID FERTILISERS IN AGRICULTURAL CROPS: A REVIEW
Keywords: phosphate, nitrogen, placement, maize, sugar beet, potatoes, cereals, rice.
Fertiliser placement resulted in considerable progress in regions where fertiliser use efficiency was very low. This generally concerns the phosphate and nitrogen containing fertilisers. Phosphate ions are quickly adsorbed in soils with low phosphate levels, whereas nitrogen losses appear via denitrification, volatilisation, leaching or fixation. The magnitude of both P-adsorption and N-losses depends mainly on soil type, tillage, fertiliser management, crop rotation and weather conditions.
The uptake of phosphate is affected by many factors, particularly by root density. In crops with wide row distances and slow juvenile growth, a band placement of phosphate leads to better availability and enhances the growth of young seedlings in the early stages. Best results with phosphate placement have been obtained in maize, sugar beets and potatoes. Fertiliser placement in maize has been introduced in some areas of North America and in Germany.
Fertiliser types used are ammonium polyphosphate (10+15), di- and monoammonium phosphate (16+46, 11+52) and ammonium nitrate containing NP-fertiliser (26+14), which is applied to cereal growing areas in eastern Sweden on account of the minimal rainfall after sowing.
Autumn application of nitrogen – as carried out in the Prairie Provinces of Canada – has been found to be less effective than spring application, because nitrogen was partially lost by denitrification, immobilisation or by leaching. Additionally, nitrogen losses by volatilisation were observed in rice. This applies more to urea than to ammonium sulphate. The losses can be minimised not only by a better distribution, but also by a better placement of fertiliser or by the use of nitrification inhibitors. A great deal of research is being carried out in Japan and the Philippines.
H Knittel, BASF Agricultural Research Station, Limburgerhof, Germany.
20 Pages, 8 Figures, 4 Tables, 48 References
EXPERIMENTS WITH FERTIGATION AS A METHOD OF PLACEMENT OF FERTILISERS IN FRUIT GROWING IN THE NETHERLANDS
Keywords: fertigation, liquid feeding, trickle irrigation, apples, nitrogen nutrition.
Due to the humid-temperate climate of The Netherlands, there was little interest in trickle irrigation and fertigation in orchards until 10 to 15 years ago. Experiments showed that drip irrigation alone promoted shoot growth, but since flower bud formation was poor, fruit production could not keep pace with the increased vegetative growth. However, drip irrigation in combination with fertilisation resulted in strong shoot growth, good leaf colour, and sufficient flower bud formation to increase production.
These results led to a new fertigation project with special emphasis on the many dynamic processes taking place in the soil during the growing season. Although the experiments are still in their early stages, some results of a field trial are presented.
The distribution pattern of nitrate in the soil analysed in mid-July and analysis of leaf-nutrient concentration showed that the efficiency of nitrogen uptake by young trees was much higher with fertigation than with broadcast fertilisation.
In the first year no differences in root development were found when fertigation was compared with broadcast fertilisation.
J A Kipp, Research Station for Fruit Growing, Wilhelminadorp, The Netherlands (seconded from the Institute for Soil Fertility, Haren)
16 Pages, 8 Figures, 1 Table, 9 References.