Increasing sustainable production and soil fertility on broad-acre organic farms
Project ID:
01P33
Project type:
Research
Start date:
01/07/2001
Completion date:
30/12/2004
Project status:
Current
Project leader:
,
Lead agency:
NSW DPI
Locations:
Wagga Wagga Agricultural Institute
Project Details
Objectives:
The principle aim is to develop innovative management for soil and pasture leading to fertility gains consistent with higher cereal yields and more frequent cropping on organic farms. A supplementary aim is to improve information for decision support on the timeliness of converting pasture to crop production on organic farms.
Methodology:
Field trials will be established on two organic cereal producing farms, contrasting rainfall and soil type. In each case the location will be representative of paddocks that have declined in phosphorus fertility to sub-optimal levels. At each location soil amendment with reactive rock phosphate will be undertaken and co-application of elemental sulphur will be applied in one treatment. The purpose of the sulphur application is to allow its oxidation by bacteria to increase soil acidity in the direct vicinity of the phosphate rock so as to enhance dissolution of the latter. Additional soil treatments will compare the efficacy of ground reactive rock phosphate with that of the granulated form, and assess the effect of soil liming on phosphate supply from soil and rock sources. In terms of pasture treatments, at the more acidic, higher rainfall site, the productivity of an acid tolerant pasture (serradella, yellow lupin), and its effect on phosphorus cycling, will be compared with that of a tradition pasture (clover / ryegrass). At the less acidic, lower rainfall site, the effect of mulching pasture (green manure) on phosphorus availability will be compared with harvesting pasture for forage. After two to three years of pasture, plots will be established to cereal crops to measure the impact of the soil and pasture treatments on crop yield and grain protein. Soil pH and phosphorus availability, plant yields and nutrient composition will be monitored regularly. Soils will be further resolved for the distribution of phosphorus in mineral and organic fractions, and mineral nitrogen availability.
To determine the relationship between soil profile mineral nitrogen, expected and actual yields of cereal crops, several organic farms will be sampled. Soil nitrate to 1 m will be assessed at crop emergence. Cereal biomass, nitrogen content, and yield will be determined later in the season. Water-limited potential yield will be estimated from the available mineral nitrogen at sowing, and seasonal rainfall, and compared to actual yield. Additional soil nutrient analyses will be used to identify discrepancies in actual and potential yield, to assist future paddock management.
To assess the role of organic farming in improving soil health, a number of farms and paddocks will be surveyed for their soil nutrient status, organic carbon concentration and microbial biomass level and activity.
Industry relevance:
Reported lower cereal yields and frequency of cereal cropping on organic farms constrains farm profitability, particularly in times of low livestock prices and high grain prices. A literature review indicated that the soil phosphorus status on organic farms can be sub-optimal and may explain the practice of long pasture phases to perhaps bring sufficient phosphorus into the rapidly exchangeable phase and / or increase soil nitrogen fertility adequately for productive cropping. As a wider survey of organic farms subsequently verified the low phosphorus status of some organic cereal producing enterprises, then a successful strategy to restore or enhance plant available soil phosphorus could lead to more productive and frequent cereal cropping. It was also found in pre-project discussions, that organic farmers do not use objective criteria for converting pasture to crop. Defining objective soil nutrient criteria to assist this decision making will prevent over-long pasture phases or avoid too-early conversion. Knowledge on soil health of organic farms will help organic farmers understand whether their farming practices are relevant and optimal.
Target audience:
Producers, farming groups, industry agronomists, fertiliser companies.
Project leader:
Dr Jeffrey EVANS (no longer employed by NSW Ag)
Ph. Fax.
Additional project members:
Miss Latarnie MCDONALD (no longer employed by NSW Ag)
The information contained in this web page is based on knowledge and
understanding at the time of writing. However, because of advances in knowledge, users are
reminded of the need to ensure that information upon which they rely is up to date and to
check currency of the information with the appropriate officer of New South Wales
Department of Agriculture or the user’s independent adviser.
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