Effects of rates and times of nitrogen application on the production and composition of dairy pastures in Waikato district, New Zealand

Abstract

Nitrogen (N) was applied at 0, 25, 50, and 100 kg/ha in consecutive months from March to August 1980 and 1981 to pastures at No.2 Dairy, Ruakura. Pasture production was measured in 5 harvests and the botanical and chemical compositions of the pastures were determined in harvests I and 4. N usually increased pasture growth in harvests I and 2 but reduced it in harvests 4 and 5 because of reduced clover content. N concentration in pasture followed a similar pattern. Responses increased but efficiency of N decreased with increasing rates of application. Efficiency of N applied in winter-early spring was twice that applied in autumn. Responses in early spring depended upon the rate of pasture growth at the time. In additional trials, 0, 25, and 50 kg Nzha was applied either 2 or 3 times to the same areas. Efficiency of N from repeated and from single applications was similar.

Influence of time of application on the fate of15N-labelled urea applied to dairy pasture

“…The influence of time of application on the pattern of pasture response to N is similar to that reported by Feyter et al (1985). The response was more prolonged when N was applied during the period of slow pasture growth.…”

“…The response was more prolonged when N was applied during the period of slow pasture growth. Total pasture growth was increased least after the May application of N as found by others (e.g., O'Connor 1982;Feyter et al 1985).…”

“…In contrast, Feyter et al (1985) measured larger residual responses from N applied in June than in August (although initial responses were smaller). These differences may be caused by differences in soil temperature affecting immobilisation.…”

“…Various studies (e.g., O'Connor 1982;Feyter et al 1985) have shown that total pasture responses from N applied in winter or early spring were up to twice those from the autumn application. The reasons for variability in pasture response to N fertiliser have been attributed to differences in pasture growth rate and soil N availability (e.g., Ball & Field 1982).…”

Variability in pasture nitrogen fractions and the relationship to bloat

“…If this is a causative factor in bloat severity,results from the field experiment suggest thatN fertiliser maybe usedto reducebloatseverity becauseof thedominating effectofcloveronsoluble proteinN in a sward and the decline in soluble protein N in clover as a result of N addition. Furthermore, N application causesa reduction in the clover content of a sward which lasts for several months (Ledgard & Saunders 1982;Feyter et al 1985) and this may also reduce the incidence of bloat 241…”