Nitrogen fertilizer value of activated sewage derived protein: Effect of environment and nitrification inhibitor on NO 3 - release,soil microbial activity and yield of summer cabbage

Yield response of summer cabbage (Brassica oleracea varcapitata cv. Hispi F₁) to N applied as organic (activated sewage sludge derived protein [Protox] and dried blood) and inorganic (ammonium nitrate, ammonium sulphate, sodium nitrate and urea) fertilizers was compared in relation to the N availability characteristics of the materials. Effects of the nitrification inhibitor dicyandiamide (DCD) on N release, crop yield and N status were also assessed. In addition CO₂ efflux was measured from amended soil to determine effects of fertilizer application on soil microbial activity. The organic N sources were mineralized quickly on application to soil and exhibited similar patterns of NH₄-N depletion and NO₃-N accumulation as functions of thermal-time as with mineral fertilizers. However, the yield response to organic N was marginally smaller (though not significantly) compared with mineral forms; probably because less N was released to the crop. This was reflected in smaller total N concentrations and N recoveries in plants supplied with organic fertilizer. Applied DCD increased the thermal-time for complete nitrification of NH₄-N sources and raised the total N content of the crop, but had no overall effect on crop growth. In contrast to inorganic N sources which generally reduced CO₂ efflux from soil, application of protein-based fertilizers increased the rate of soil microbial activity directly by raising substrate availability. Sewage sludge derived protein provided an effective alternative to mineral fertilizers for the nutrition of summer cabbage whilst minimising stress of the soil environment which may occur following the application of conventional forms of inorganic N to the soil.     

Effect of fertilization on organic and microbial biomass nitrogen using15N under corn (Zea mays L.) in two Quebec soils

Changes in soil organic N following fertilizer N applications are related to soil quality and subsequent N uptake by plants. Recovery of fertilizer N as organic N and soil microbial biomass N within two corn (Zea mays L.) fertilization systems was studied using¹⁵N on a Chicot soil (fine-loamy, mixed, frigid, Typic Hapludalf) and a Ste. Rosalie soil (fine, mixed, frigid, Typic Humanquept) in southwestern Quebec in 1989 and 1990. The two fertilization systems studied received a recommended rate of 170-44-131 kg (normal rate) and a high rate of 400-132-332 kg of N-P-K per hectare. Increasing fertilization rates above normal increased microbial biomass N immobilization with a subsequent greater N release. Higher fertilization rates significantly increased both the magnitude of soil microbial biomass N and microbial fertilizer N recovery in the soil microbial biomass.     

Recovery of mineral N fertilizer in herbage and soil organic matter in grasslands of the Massif Central,France

Nitrogen fluxes in intensive grassland have been studied in lysimeters (3 m², 0.80 m deep) with¹⁵N labelled fertilizers (360 kg N/ha). The harvested fertilizer uptake efficiency was around 52% of which 45% was exported and 7% stored. Leaching losses were very low, despite considerable drainage. The immobilization of mineral N during the first year was very important (40–50%) and the remineralization was slight. The N recovered in soil after two years was 40% of N-fertilizer applied of which 19% is contained in free organic matter and 21% in organo-mineral fraction (< 50µ). The immobilization of N is greater in the surface top of soil: 68% in the first 5cm. Beneath a growing crop the in-depth migration of the N takes place exclusively through root growth. The global N balance and cycle in soil were discussed.

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Mots clés bilan de l'azote, lixiviation, minéralisation, immobilisation, matière organique, prairieRésumé La dynamique de l'azote sous une prairie temporaire a été étudiée en cases lysimétriques (3 m², 0,80cm profondeur) en utilisant de l'engrais marqué à¹⁵N (360 kg N/ha). Le coefficient d'utilisation par les parties aériennes a été d'environ 52% dont 45% exporté et 7% mis en réserve. Les pertes par lixiviation ont été minimes malgré un drainage important. L'organisation de Nmineral pendant la première année a été importante (40-50%) et la reminéralisation ultétieure très faible. Après deux ans, 40% de N apporté comme engrais a été retrouvé dans le sol dont 19% dans la matière organique libre et 21% dans les fractions organo-minerales (< 50µ). L'immobilisation de l'azote est supérieure dans les couches superficielles du sol: 68% à la profondeur 0–5 cm. Sous une culture en croissance la migration en profondeur a lieu exclusivement par la croissance racinaire. Le bilan de N et la cycle de l'azote dans le sol ont été établis.

     

Light fraction organic N, ammonium, nitrate and total N in a thin Black Chernozemic soil under bromegrass after 27 annual applications of different N rates

Anadequate supply of N for a crop depends among others on the amounts of N thataremineralized from the soil organic matter plus the supply of ammonium andnitrateN already present in the soil. The objective of this study was to determine thebehaviour of light fraction organic N (LFN), NH₄-N, NO₃-Nand total N (TN) in soil in response to different rates of fertilizer Napplication. The 0–5, 5–10, 10–15 and 15–30cm layers of a thin Black Chernozemic soil under bromegrass(Bromus inermis Leyss) at Crossfield, Alberta, Canada,weresampled after 27 annual applications of ammonium nitrate at rates of 0, 56,112,168, 224 and 336 kg N ha^–1. The concentration andmass of TN and LFN in the soil, and the proportion of LFN mass within the TNmass usually increased with N rates up to 224 kg Nha^–1. The increase in TN mass and LFN mass per unit ofNadded was generally maximum at 56 kg N ha^–1 anddeclined with further increases in the rate of N application. The percentchangein response to N application was much greater for the LFN mass than for the TNmass for all the N rates and all soil depths that were sampled. Mineral N intheform of NH₄-N and NO₃-N did not accumulate in the soil at 112 kg N ha^–1 rates, whereas theiraccumulation increased markedly with rates of 168 kg Nha^–1. In conclusion, long-term annual fertilization at 112 kg N ha^–1 to bromegrass resulted insubstantial increase in the TN and LFN in soil, with no accumulation ofNH₄-N and NO₃-N down the depth. The implication of thesefindings is that grasslands for hay can be managed by appropriate Nfertilization rates to increase the level of organic N in soil.