Information
Level 2 Detail of experimental conditions (what might be found in a journal paper or project brief in Hydstra)
Description of study
What?
Nitrogen fixation in legumes, net N mineralisation, and utilisation of soil-derived nitrogen, as well as the extent of drainage and NO3− leaching below 1.5m of soil was examined on crop and pasture rotations.
When and Where?
The experiment was conducted 14km west of Moora, Western Australia and commenced in 1994. Rainfall in the region is concentrated from May – June to October, conditions are hot and dry throughout summer. The soil is classified as yellow sand (Table 1).
How?
A rotation experiment was conducted which included a 2 year rotation of 1 year lupin followed by one year wheat, and a three year rotation comprising a 2 year subterranean clover-capeweed annual pasture followed by wheat (Table 2).
Crop biomass (t DM/ha) and N content (kg/ha) of lupin and wheat were measured at tillering, anthesis, and harvest, with the 15N composition of lupin also determined. Measurements were conducted across 0.86 by 0.54 m quadrats per plot. Measures of N content and 15N natural abundance were also collected from whole top samples. The % of N in legumes from atmospheric N2(%Ndfa) was calculated from levels of 15N abundance.
Root length densities were measured using material recovered from soil sampled using a 100 mm sand auger. The quantity of N in root material was calculated using the %N contents from studies previously conducted on lupin and wheat below-ground biomass at the site location.
Net N mineralisation for the fallow period was determined by subtracting the quantities of inorganic N in soil to a depth of 1.5 m at grain harvest from the quantity measured from the same soil depth at the break of the season. Growing season net N mineralisation measurements were also taken,and change in inorganic N compared between soil cores over a period of 3 – 5 weeks.
The soil water content (% v/v) was measured using time domain reflectometry (TDR) during the 1995 and 1996 growing seasons. TDR probes (0.4 m in length) were placed horizontally in soil at depths of 0.2, 0.3, 0.5, 0.7, 0.9, 1.2 and 1.5 m under 1 replication of the lupin and wheat phases of the lupin-wheat rotation. The surface probe was positioned horizontally at 0.1m in 1995, and in 1996 this probe was installed obliquely to provide measurements of soil water (SW) between 0.02 and 0.1m. The SW content was measured at midnight of each day. The SW content of each layer was calculated by assuming that each probe measured SW content of the surrounding 0.05m of soil.
Daily actual evapotranspiration (Ea) was measured using the Bowen ratio technique. A single Bowen ratio unit was placed in an adjacent wheat field from 26 July to 16 October 1995, and in the same paddock in lupin from 12 July to 30 September 1996. Ea was calculated from Penman estimates of evapotranspiration (Ep) either when the Bowen ratio unit was not in place (10 May-26 July 1995 and 2 July-12 July 1996) or during short periods of malfunction.
The quantities of NO3− in the soil profiles were measured by soil sampling and the use of ceramic suction cups. Soil samples to 1.5 m were collected on 19 March, 14 June, 21 July, 26 September, and 29 November 1994; 12 April, 18 May, and 27 November 1995; and 18 June and 5 December 1996. Ceramic suction cup samples were collected on 11 and 27 July and 15 August 1995, and 26 July and 2, 8, and 15 August 1996.
In 1994, the quantity of NO3− leached below 1 m was measured using an anion exchange resin trap installed at the bottom of intact soil columns.
Nitrogen budgets for each rotation treatment were constructed for the 1995 and 1996 growing seasons. The change in mineral N to 1.5 m, between prescribed sampling times, was assessed in terms of net mineralisation, plant uptake of soil-derived N, and potential recycling of N during grazing.
Project administration
Site identifier code: na
Principal investigator: Anderson G.C.
Principal data manager: na
Principal organizations: Grains Research and Development Corporation, Co-operative Research Centre for Legumes in Mediterranean Agriculture, University of Western Australia, CSIRO Plant Industry, Agriculture Western Australia
Data custodian: Co-operative Research Centre for Legumes in Mediterranean Agriculture
Key co-operators: Ninnan Farms
Data access policy: Research has been published but base data is not archived
Planned pathway for data: completed study, no evidence of formal database records.
Data warehousing: for ongoing studies -na
Planned data upload frequency: for ongoing studies -na
Key references and sources of this data synthesis
These data summaries have been extracted from:
- i. Anderson, G. C., Fillery, I. R. P., Dunin, F. X., Dolling, P. J., and Asseng, S. (1998) Nitrogen and water flows under pasture-wheat and lupin-wheat rotations in deep sands in Western Australia 1. Nitrogen fixation in legumes, net N mineralisation, and utilisation of soil-derived nitrogen. Australian Journal of Agricultural Research 49: 329-343.
ii. Anderson GC, Fillery IRP, Dunin FX, Dolling PJ, Asseny S. 1998. Nitrogen and water flows under pasture-wheat and lupin-wheat rotations in deep sands in Western Australia 2. Drainage and nitrate leaching. Australian Journal of Agricultural Research. 49: 345 – 361.
Keywords:
N loss, efficiency N use, ‘spared’ N, subterranean clover, capeweed, time domain reflectrometry