Influence of soil type, crop management and weather on the recovery of ¹⁵N-labelled fertilizer applied to winter wheat in spring

Abstract

SUMMARY15N-labelled fertilizer was applied, in spring, to winter wheat crops in nine experiments in eastern England over a period of 4 years. Five were on Batcombe Series silty clay loam, two on Beccles Series sandy clay loam (with a mole-drained clay subsoil) and two on Cottenham Series sandy loam. In three of the experiments, different rates of fertilizer N were applied (up to 234 kg N/ha); in the others, a single rate (between 140 and 230 kg/ha) was used.Recovery of fertilizer N in the above-ground crop (grain, chaff, straw and stubble) ranged from 46 to 87% (mean 68%). The quantity of fertilizer N retained in the soil at harvest was remarkably constant between different experiments, averaging 18% where labelled N was applied as 15NH415NO3, but less (7–14%) where K16NO3 was applied. Of the labelled N present in soil to a depth of 70 cm, 84–88% was within the cultivated layer (0–23 cm).L70 = 5(± 1 63) + 0·264(±00352) R3accounted for 73% of the variation in the data where: L70 = percentage loss of fertilizer N from the crop: soil system, defined as percentage of labelled N not recovered in crop or in soil to a depth of 70 cm at the time of harvest; R3 = rainfall (in mm) in the 3 weeks following application of N fertilizer.There was a tendency for percentage loss of fertilizer N to be greater when a quantity of N in excess of that required for maximum grain yield was applied. However, a multiple regression relating loss both to rainfall and to quantity of N applied accounted for no more variance than the regression involving rainfall alone. In one experiment, early and late sowing were compared on the first wheat crop that followed oats. The loss of N from the early-sown crop, given fertilizer N late in spring, was only 4% compared with 26 % from the later-sown crop given N at the same time, so that sowing date had a marked effect on the loss of spring-applied fertilizer N.Uptake of unlabelled N, derived from mineralization of organic N in soil, autumn-applied N (where given) and from atmospheric inputs, was < 30 kg/ha on a low organic matter (0·08% total N) sandy soil but > 130 kg/ha when wheat followed potatoes or beans on soil containing c. 0·15 % total N. Unlabelled N accounted for 20–50% of the total N content of fertilized crops at harvest. About 50% of this unlabelled N had already been taken up by the time of fertilizer application in spring and the final quantity was closely correlated with the amount present in the crop at this time. Applications of labelled fertilizer N tended to increase uptake of unlabelled N by 10–20 kg/ha, compared to controls receiving no N fertilizer. This was probably due to pool substitution, i.e. labelled inorganic N standing proxy for unlabelled inorganic N that would otherwise have been immobilized or denitrified.

Nitrate Nitrogen in the Soils of Eastern Poland as Influenced by Type of Crop, Nitrogen Fertilisation and Various Organic Fertilisers

“…According to Chaney (1990), the non-linear effect of N-fertilisation on the nitrate(V) content in soil has environmental and economic implications. Powlson et al (1992) indicate that over-fertilization will not only be wasteful but may also lead to ground and surface water pollution.…”

A Dynamic Decision-Making Tool for Calculating the Optimal Rates of N Application for 40 Annual Crops While Minimising the Residual Level of Mineral N at Harvest

“…The AzoFert ® model assumes that mineral N in the soil (residual N, mineralised N and fertiliser N) is fully available to the crop both temporally (between the opening of the balance sheet and crop harvest) and spatially (regardless of the distribution of water, nitrogen and roots in the soil profile). This assumption was verified for the N fertilisation of annual crops in northern Europe, where drainage stops at the end of winter and where water availability frequently does not limit N uptake over the growing season [17,18]. However, this condition is not always met in other climates, such as during droughts under Mediterranean conditions or under rainy conditions.…”

“…The functions used for N immobilisation and volatilisation of ammonia were derived from 15 N experiments that demonstrated the microbial immobilisation of added fertiliser N and the incomplete recovery of the added N by different crops in the temperate climate of northwestern Europe [17,18].…”

“…This method, which is widely used for fertilisation management in France, was evaluated under a wide range of environmental conditions [14]. Over the past twenty years, research findings on the following have provided a basis for improving fertilisation recommendation tools, particularly when considering the dynamics of the soil N cycle over time: characteristics of animal and organic waste and crop residues recycled to soils and their potential mineralisation [15,16] and the dynamics of fertiliser N after application, as well as the determinants of fertiliser N recovery in crops, particularly using nitrogen-15 (15N) techniques [17,18]. The objective of this study was to develop AzoFert ® software to improve the calculations underlying fertiliser N recommendations, in order to reduce excess mineral nitrogen fertilisation without affecting crop yields, by making dynamic use of the balance sheet method for a wide range of crops, soils, organic and mineral fertilisers and pedoclimatic conditions.…”

Fate of residual15N-labeled fertilizer in dryland farming systems on soils of contrasting fertility

“…Dai et al (2013) reported that when N application rates increased from 0 to 320 kg ha −1 , NO 3 --N leaching below 100 cm depth increased from 15 to 258 kg ha −1 during the summer fallow, in an experiment on the south of the Loess Plateau, China. The mechanisms of the residual N loss may include nitrate leaching, and denitrification (Powlson et al 1992;Macdonald et al 1997;Ju et al 2009). Further study is needed to estimate the relative contributions of these different loss mechanisms, and measures to control residual N loss during summer fallow are also needed.…”