Guideline Index

Chapter 1: Fert$mart Planning

1.3 Identify soil and nutrient related issues

Before considering the plant nutrient requirements, it is important to identify if there are other soil and nutrient related issues. There could be limiting factors (other than nutrients) that need to be addressed to get the best value out of fertilisers. Some factors cannot be changed economically (e.g. highly sodic or saline soils) and land use and production goals in these areas need to be matched accordingly. Farm scale nutrient efficiencies are also considered in this step. Are there opportunities to use nutrients more strategically across the farm, e.g. better distribution of effluent?

1.3.1 Identify soil issues

Limiting factors can be identified using field observations described in Sections 1.1.7 and Section 1.1.8 in combination with the soil tests. Some factors can only be observed in the field (e.g. compaction, pugging, and waterlogging) while others may show signs in the field, but need to be confirmed with soil tests (e.g. salinity, sodicity and acidity). Chapters 4 to 7 of this manual discuss soil issues. Now work out cost effective management options where they exist. It may be necessary to prepare a program and budget to remedy these over a longer time period.

1.3.2 Identify irrigation water quality issues

Poor quality irrigation water can be harmful to crops, soil and irrigation equipment. This can result in lower production and poor fertiliser use efficiency. Check the water analysis for the five salinity and sodicity criteria.

More on irrigation water quality

1.3.3 Identify limiting crop/pasture condition issues

Production can also be limited by crop and pasture condition (e.g. species, plant population, diseases, pests and weeds). Crops and pastures in good condition and suited for the purpose will use soil nutrients more efficiently than unhealthy and weedy stands. See Chapter 15.5.1 for more on species suitability.

1.3.4 Identify farm-scale nutrient issues and options

Prepare a farm nutrient budget (See Nutrient Budgeting, Chapter 15.6 ) to work out the quantities of nutrients coming onto, and leaving the farm. The nutrient budget will show whether there is a whole farm nutrient surplus or deficit. Phosphorus, potassium and sulphur are generally accounted for in the nutrient budget. In situations where a nutrient surplus exists there may be an opportunity to treat areas more strategically and reduce nutrient costs. This could apply to both fertiliser and effluent treated areas on the farm. When nutrients exported from the farm in produce exceed nutrients brought onto the farm, the deficit can be used to estimate the total nutrient requirements to maintain production.

It is also important to look for nutrient build up areas and cease further applications of nutrients already in abundance. Nutrient maps provide a good visual comparison of nutrient levels across the farm. Alternatively, nutrient levels in each paddock/FMZ can also be compared with the soil fertility guidelines using a graph or table (See Chapter 15.10 and Chapter 16.2.3 ).

This information also helps to identify which FMZs will benefit most from the dairy effluent, provided it is practical to get the effluent onto that area of the farm. Estimate the quantity of effluent produced each year, and the nutrient composition to work out its value. Estimating the dollar value of effluent (equivalent fertiliser cost) helps to justify any additional costs required to use effluent more strategically around the farm. Explore cost effective options to improve effluent distribution – See Chapter 13 , ‘Using Dairy Effluent’.

For more information on retaining and optimising nutrient use on dairy farms refer to Chapter 10, Keeping Nutrients on Farm.