Effect of trickle fertigation with three forms of nitrogen on soil pH, levels of extractable nutrients below the emitter and plant growth

Abstract

The effects of application of nitrogen as calcium nitrate, urea or ammonium sulphate at two rates through the trickle irrigation system on pH and nutrient status of the wetted volume of soil below the emitters and on growth and nutrition of courgette (zucchini) plants (Cucurbita pepo L.) was investigated.Soil acidification, caused by nitrification, occurred to a large extent in the volume of soil immediately below the emitters in the urea and ammonium sulphate treatments. Acidification was greater at the high rate of N addition and more pronounced with ammonium sulphate than urea. A significant amount of applied urea appeared to move through the soil as urea and consequently, at the same rate of N addition, levels of ammonium were lower directly below the emitter and those of nitrate were higher further away from the emitters for the urea than ammonium sulphate treatments. Soil acidification below the emitters resulted in significant decreases in levels of exchangeable Ca, Mg and K and increases in levels of exchangeable A1, EDTA-extractable Fe, Mn, Zn and Cu and bicarbonate-extractable P Vegetative growth and harvestable yields of courgettes were increased by both irrigation and nitrogen applications. Vegetative growth was generally greater at the low rate of N addition than at the high one and generally followed the order calcium nitrate > urea > ammonium sulphate. However, fruit yields followed the order urea > ammonium sulphate > calcium nitrate and were larger at the high rate of N for urea and ammonium sulphate treatments and unaffected by rate for the calcium nitrate treatments. It is suggested that with fertigation, the form of applied N can have significant physiological effects of plant growth and yields because N may be applied into the root zone on numerous occasions during the growing season.

Fertirrigação com diferentes doses de NPK e seus efeitos sobre a produção e qualidade de frutos de laranja (Citrus sinensis O.) 'Valência'

“…O mesmo comportamento pode ser observado para os valores de Mg. Segundo Haynes & Swift (1987), a acidificação do solo na região atingida pela irrigação resulta em significativa redução nos teores de Ca, Mg e K extraídos na análise do solo amostrado nestes locais. O comportamento do íon K observado no presente experimento não segue o padrão estabelecido por estes autores.…”

Crescimento e produtividade da bananeira cv. Grande Naine sob diferentes combinações de nitrato de cálcio e ureia

“…Uma forma de contornar esse problema é o uso de uma fonte amoniacal conjugada com uma fonte nítrica. Haynes & Swift (1987) estudaram o efeito da aplicação de nitrato de cálcio, sulfato de amônio e ureia em duas doses, por meio de sistemas irrigados por gotejamento sobre o crescimento e a produção do mamoeiro. Os autores verificaram aumento no crescimento e na produção do mamoeiro com a aplicação de nitrogênio.…”

Fertigation for Effective Nutrition and Higher Productivity in Banana - A Review

“…Edwards et al, (1982) observed that application of NH 4 NO 3 through drip irrigation system decreased the soil pH in the top 30cm. Haynes and swift (1987) concluded that with increasing soil acidification, the leaching of cations viz., Ca 2+, Mg 2+ , K + and Na were also in greater amounts. Soil acidification appeared to inhibit nitrification as levels of NO 3 clearly decline below pH 5.5 and at the same time levels of NH 4+ increased greatly.…”

“…Soil acidification caused by nitrification, occurred to a large extent in the volume of soil immediately below the emitters when fertigated with urea and ammonium sulphate (Haynes and Swift, 1987).…”