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«International 17 Workshop th Nitrogen The was jointly organised by Teagasc and AFBI Printed by Print Depot Suggested citation Authors, 2012. Title ...»

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a b NH4+-N (mg kg -1)

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Figure 1. Interaction of date vs.

depth effects on soil NH4+-N (a) and NO3- -N (b) during the rice season, in 2011.

SPAD-readings in ‘Ariete’ rice Y-leaf in the open field were significantly smaller (38) than values obtained in plants cropped in CO2 and temperature chambers (41). SPAD-values above 35, i.e., greater than 1.4 g N m-2 leaf area indicate a proper crop N status (Figueiredo, 2011).


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Figure 2. Interaction of date vs.

treatment effect on SPAD-values in Y-leaf of ‘Ariete’ rice, during 2011 growth.

4. Conclusions Ammonium increased in the soil profile after flowering stage, but NO3- was maintained low.

Flooding increased the soil pH (from 4.7 to about 6) and was apparently higher in CO2 chambers (7.5). Rice ‘Ariete’ showed a proper N status for the whole season, but a significantly higher crop N was measured inside the open top chambers (SPAD-readings: 38-41). Measurements on gaseous losses and NH4+-fixation in soil are recommended to evaluate the fertilizer-N efficiency.

Reference Figueiredo, N. 2011. Dinâmica do Azoto em Campos Alagados para Produção de Arroz, em Salvaterra de Magos.

Thesis for Master degree in Agricultural Engineering, ISA/UTL, Lisbon. p. 60.

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Influence of inter tillage on nitrate content in soil during tobacco crop growth Castelli F.a, Marchetti R. b, Orsi A.b, Sghedoni L.b a Agricultural Research Council, Bovolone Experimental Farm, Bovolone (VR), Italy b Agricultural Research Council, Research unit for swine husbandry, San Cesario sul Panaro (MO), Italy

1. Background & Objectives With the establishment of the Common Agricultural Policy (CAP), the EU subsidies to farmers are linked to their compliance with rules relating to agricultural land, agricultural production and activity. Given the high environmental impact of tobacco crop, requiring the use of large amounts of chemicals, it could be possible to provide assistance to farmers who undertake the implementation of cropping practices capable of reducing the environmental impact of tobacco cultivation. In a previous experiment we detected unusually high amounts of inorganic N in the top soil cropped with Virginia Bright tobacco (Nicotiana tabacum L.), in the early stages of the growth season (Marchetti et al., 2006). Nitrogen excess affects negatively tobacco leaf quality and can give rise to water pollution by nitrates. Tobacco, being a row crop, needs some tillage operations (ST) during the crop cycle (usually reported as “inter tillage”) to reduce weed growth, improve soil aeration and water infiltration, and prepare row ridges. As tillage is known to trigger N mineralization (Dinnes et al., 2002), we hypothesized that ST operations, by aerating the soil, could foster the organic-N mineralization, and consequently cause an increase in the soil nitrate N levels.

2. Materials & Methods A field experiment was carried out in 2007, 2008 and 2010 at Bovolone, near Verona, Italy, on a loam soil, cropped with Virginia Bright tobacco, cv. K 326. The compared treatments were: 2 tillage intensity levels (in-row cultivation + ridging, ST, vs. non tilled soil, NT)  2 fertilizer N rates 0 (N0) and 80 (N80) kg N ha1. The experimental design was a splitplot, with the tillage level factor in the main plot, and the N rate factor in the sub-plots (256 m2), with 3 replications. Nitrogen fertilizer was applied as calcium nitrate at the beginning of June, a month after tobacco transplanting. In-row cultivation and ridging was carried out in June. Tobacco leaf yield was determined as the sum of yields at 3 priming dates. Leaf yield and aboveground biomass were obtained from 20 plant samples per plot. Crop N (Kjeldahl method) removal was calculated on the basis of plant dry matter and N concentration in the plant tissues. The nitrate-N content in soil (NO3-N) was determined colorimetrically with an automatic analyzer in samples from the top 00.20 m layer, in the JuneJuly period, on 6 dates, including before and after the ST operations. A mixed model was used for the statistical analysis of leaf yield, crop N removal and NO3-N content in soil. In this paper, means of 3-year measurements are reported. Multiple comparisons of the means were carried out. Factor effects were considered significant at P 0.05.

3. Results & Discussion Tobacco-leaf yield in the tilled plots was slightly higher than in the non tilled (4.9 vs. 4.6 t ha-1;

Figure 1). Nitrogen fertilization (N80) increased leaf yields approximately by 1 t ha-1, compared with the N0 rate (5.3 and 4.2 t ha-1, respectively). The amount of N removed by the aboveground biomass (AGB) was remarkably higher in plots supplied with N fertilizer (+65%, compared with N0). Differences due to N fertilization were still more emphasized in the case of the nitrate-N amount measured in the plant tissues (+274%, compared with N0). High nitrate-N contents in tobacco leaves following N fertilization had already been observed in previous tobacco experiments Nitrogen Workshop 2012 (Castelli et al., 2011). Nitrates are considered dangerous as precursors of carcinogenic nitrosamines.

No significant differences between treatments were associated with tillage intensity.

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Figure 1. Influence of tillage intensity level (inter tillage, ST, vs.

no tillage, NT) and fertilizer N rate (non fertilized crop, N0, vs. fertilized, N80) on tobacco leaf yield, N removal in the above ground biomass (AGB) and NO3-N content in the AGB. Means followed by the same letters are not significantly different for P0.05 probability level.

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4. Conclusion An important positive interaction effect on soil nitrate levels was observed between N fertilizer and inter tillage; specifically, soil nitrate levels were much higher in the soil of tilled and fertilized plots.

Crop fertilization with 80 kg N ha-1 positively influenced tobacco leaf yields, whereas inter tillage did not. In other words inter tillage, coupled with N fertilization, did not lead to increased crop yields, but instead increased tobacco leaf- and soil nitrate content, which is detrimental for the technological quality of tobacco leaves, as well as for the quality of the environment. As tobacco needs inter tillage for weed control and plant ridging, it is important to take into account the effect of inter tillage on soil N availability by properly reducing the fertilizer N supply to tobacco crop.

References Alvarez, R. and Steinbach, H.S. 2009. A review of the effects of tillage systems on some soil physical properties, water content, nitrate availability and crops yield in the Argentine Pampas, Soil and Tillage Research 104, 1-15.

Castelli, F., Ceotto, E. and Contillo, R. 2011. Reduced N supply limits the nitrate content of flue-cured tobacco, Agronomy for Sustainable Development 31(2), 329-335.

Dinnes D.L. et al. 2002. Nitrogen management strategies to reduce nitrate leaching in tile-drained mid-western soils, Agronomy Journal 94, 153–171.

Marchetti, R., Castelli, F. and Contillo, R. 2006. Nitrogen requirements for flue-cured tobacco, Agronomy J. 98, 666


Nitrogen Workshop 2012

Irrigation and nitrogen fertiliser management effects on nitrate leaching losses from crop rotations Thomas, S.M.a, Francis, G.S.b, Waterland, H.E.a, Zyskowski, R.F.a,Tabley, F.J.a, Gillespie, R.N.a, Sharp, J.M.a, Fraser, P.M.a a New Zealand Institute for Plant & Food Research Limited, Private Bag 4704, Christchurch, New Zealand.

b AgResearch, Private Bag 4749, Christchurch, New Zealand

1. Background & Objectives The effects of land use change and intensification on groundwater contamination by leached nitrate (NO3) are of international concern. Both farmers and policy makers need tools to predict the effects of land management decisions on groundwater quality. However, there is a lack of appropriate tools available to these users. In New Zealand there are also few data available to validate predicted NO3 leaching losses from crops and most of these data are from studies where only winter measurements have been made. However, the increasing use of irrigation and large fertiliser inputs for growing high value crops increases the likelihood of leaching losses during other seasons. The objectives of this three-year field study were to (i) quantify how NO3 leaching losses were affected by different nitrogen and irrigation management for two cropping rotations and (ii) provide data to validate components of the APSIM (Agricultural Production Systems Simulator) model (Keating et al., 2003).

2. Materials & Methods A field experiment was established in spring 2004 at Lincoln, Canterbury, New Zealand on a moderately well drained, intensively cropped soil (Udic Ustochrept; USDA Soil Taxonomy) with two crop rotations ([i] potatoes – winter wheat – winter fallow – potatoes - triticale, and [ii] potatoes – winter fallow - spring sown peas – winter fallow – potatoes - triticale). The experiment was a randomised block design with eight replicates (each plot was 17 m long, 4.56 m wide). Each crop received three different rates of nitrogen fertiliser (N0, N1, N2) and two rates of irrigation (W1, W2) with the exception of the triticale crop that received no N fertiliser and the same irrigation treatment. Winter fallow had no crop cover. For each crop, N1 and W1 represented the optimum rates of fertiliser and irrigation. Solution samplers were installed in each plot (60 cm in the first potato crop; 150 cm in subsequent crops and fallow periods). Soil mineral N (0-150 cm) was measured in spring and autumn. Nitrate leaching losses were calculated from soil solution NO3 concentrations and drainage calculated from a soil water balance model.

3. Results & Discussion Nitrate leaching losses varied considerably in response to the irrigation and fertiliser treatments, crop rotation and winter rainfall (Table 1). Greatest leaching losses (109 kg N ha-1) were measured from potato plots with both excess irrigation and N fertiliser (W2N2), and over the wet winter fallow period in 2006 (275 mm drainage), especially following the pea crop (49 to 99 kg N ha-1).

Although there was a fallow period in 2005, the lowest leaching losses (3 to 9 kg N ha-1 in about 40 mm of drainage) were measured due to low autumn and winter rainfall; winter drainage of 100 to 150 mm is typical. Nitrate leaching losses from the N1 and N2 plots of the second potato crop were much lower when irrigation was applied at amounts to maintain a soil water deficit compared to strategies to refill the soil profile (66 to 82% lower). The amount of NO3 leached from the autumn sown triticale crop (without N fertiliser applied) was also affected by the N fertiliser management of the previous potato crop; leaching losses from the N2 treatment (39 kg N ha-1) were almost twice those of the N1 treatment (22 kg N ha-1).

4. Conclusion This work highlights the importance of (i) efficiently managing both irrigation and fertiliser N to minimise drainage and leaching losses, and (ii) planting autumn sown crops to minimise the risk of NO3 leaching over winter. This crop rotation field experiment has provided an important dataset to validate and test simulation models (e.g. APSIM) for a range of crops, water and nitrogen management conditions. The range of leaching losses under different managements also highlights the need for the development of model-based tools that farmer and policy makers can use to manage land use, and enable or limit intensification to levels that do not adversely impact the environment.

References Keating B.A., Carberry P.S., Hammer G.L., Probert M.E., Robertson M.J., Holzworth D., Huth N.I., Hargreaves J.N.G., Meinke H., Hochman Z., McLean G., Verburg K., Snow V., Dimes J.P., Silburn M., Wang E., Brown S., Bristow K.L., Asseng S., Chapman S., McCown R.L., Freebairn D.M. and Smith C.J. 2003. An overview of APSIM, a model designed for farming systems simulation. European Journal of Agronomy 18, 267-288.

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Mitigating ammonia emissions from stored dairy cow manure.

van der Weerden, T.J.a, Luo, J.b, Dexter, M.b a AgResearch, Invermay Agricultural Centre, Mosgiel, New Zealand b AgResearch, Ruakura Agricultural Centre, Hamilton, New Zealand

1. Background & Objectives In many parts of New Zealand (esp. Canterbury southwards), dairy cows are typically wintered on annual forage crops such as kale and swedes. This practice can result in significant nutrient and faecal contaminant losses to waterways, while animal treading damage can also impact on soil quality and crop utilisation. Some farmers are considering moving away from year-round grazing to instead adopt Northern Hemisphere-style housing systems, particularly over these wet winter periods. While avoiding winter grazing can reduce nitrate leaching and nitrous oxide (N2O) emissions from such soils, these systems are relatively new to New Zealand with little information on gaseous losses to determine the risk of “pollution swapping” and identify practices that reduce these emissions. Farmers utilising these housed wintering systems typically add carbon (C)-rich material such as straw or sawdust as bedding material. Increasing the amount of straw used for bedding may reduce ammonia (NH3) losses, an indirect source of N2O, during housing and storage (Clemens and Ahlgrimm, 2001; Webb et al., 2005). This paper presents findings from a 6-monthlong manure storage trial, testing the hypothesis that NH3 emissions from stored manure will decline as the input of C-rich material (straw and sawdust) increases.

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