Ag Reporting

Why is this a potential issue?

Electrical conductivity of irrigation water is a potential issue when detected at levels over the threshold because it can result in reduced productivity of cotton due to high root zone salinity. Where cotton is being grown on clay soils and irrigation water has a salinity above 5000 uS/cm, production loss of 10% or greater might occur. The level of salinity at which yield reduction occurs may be influenced by other environmental conditions such as temperature and humidity as well as the relative proportions of sodium (Na+), calcium (Ca2+) and magnesium (Mg2+) ions in soil. Remember that the report card results are for surface waters and are not relevant to bore water and that water quality varies significantly between wet and dry seasons and between sites along the same waterway.

What can be done?

Consider doing soil and water testing to confirm a salinity problem as it may be difficult to recognise salinity problems in the paddock. There can be a significant yield decline before the signs of salinity are obvious. Soil management and water management practices such as using poorer quality water on established plants can help control the impacts on production. If elevated levels are detected talk to a specialist agronomist about the results and whether any action is required. Tips for using saline irrigation water for cotton can be found from the Cotton CRC website.

Why is this a potential issue?

Electrical conductivity of irrigation water is a potential issue when detected at levels over the threshold because it can result in reduced productivity of lucerne due to high root zone salinity. Where lucerne is being grown on loam and irrigation water has a salinity above 4600 uS/cm production loss of 10% or greater might occur. The reduction in dry matter production may be influenced the cultivar used and by other environmental conditions such as the levels of exchangeable aluminium (Al3+) in the soil. Remember that the report card results are for surface waters and are not relevant to bore water and that water quality varies significantly between wet and dry seasons and between sites along the same waterway.

What can be done?

Consider doing soil and water testing to confirm a salinity problem as it may be difficult to recognise salinity problems in the paddock. There can be a significant yield decline before the signs of salinity are obvious. Soil management and water management practices such as using poorer quality water on established plants can help control the impacts on production. If elevated levels are detected talk to a specialist agronomist about the results and whether any action is required. Tips for crop management for saline irrigation water can be found at the Victorian DEPI website.

Why is this a potential issue?

Electrical conductivity of irrigation water is a potential issue when detected at levels over the threshold because it can result in reduced productivity of citrus due to high root zone salinity. Where citrus is being grown on sandy soils and irrigation water has a salinity above 4000 uS/cm production loss of 10% or greater might occur. The level of salinity at which yield reduction occurs may be influenced by the irrigation method, soil type and the rootstocks and varieties used. Remember that the report card results are for surface waters and are not relevant to bore water and that water quality varies significantly between wet and dry seasons and between sites along the same waterway.

What can be done?

Consider doing soil and water testing to confirm a salinity problem as it may be difficult to recognise salinity problems in the paddock. There can be a significant yield decline before the signs of salinity are obvious. Soil management and water management practices such as removing low hanging branches and foliage can help control the impacts on production. If elevated levels are detected talk to a specialist agronomist about the results and whether any action is required. Tips for using saline irrigation water for citrus can be found at www.bmrg.org.au

Why is this a potential issue?

What can be done?

Why is this a potential issue?

The concentration of chloride in irrigation water is a potential issue when detected at levels over the threshold because it can cause foliar injury to crops and increase uptake by plants of cadmium from soil. Chloride deposited on leaves causes foliar burn although crop species have varying sensitivity to injury from chloride in irrigation water. Irrigation water with a chloride concentration above 175 mg/L can cause foliar injury to citrus and grapes. Lucerne (350mg/L) and cotton (700mg/L) are less sensitive. Remember that the report card results are for surface waters and are not relevant to bore water and that water quality varies significantly between wet and dry seasons and between sites along the same waterway.

What can be done?

Where crops sensitive to chloride are grown, consider doing chloride testing on irrigation water. Damage caused by high-chloride irrigation water can be minimized by planting a less sensitive crop or by avoiding foliar contact by using furrow or drip irrigation. If elevated levels are detected talk to a specialist agronomist about the results and whether any action is required. When chloride concentrations in irrigation water are above 750mg/L, produce could be tested for cadmium concentration in the edible portions of the crop because chloride increases the risk of cadmium accumulation in plants. The uptake of cadmium into crops may be a risk to humans and animals eating the crop.

Why is this a potential issue?

The concentration of aluminium in irrigation water is a potential issue when detected at levels over the threshold. The trigger values relate to the total concentration of aluminium and while the aluminium is in a form that is not directly toxic to plants it can contribute to the levels of soluble aluminium in the soil. All soils contain aluminium compounds but aluminium is only an important cause of reduced productivity of field crops on acid soils. This is because as pH decreases the soluble aluminium concentration in the soil solution increases due to the enhanced solubility of aluminium oxides and the destruction of clay minerals and other silicates that occurs at low soil pH values. Soluble aluminium is toxic to roots of many plants and limits the plants access to water and nutrients. Where irrigation water with an aluminium concentration above 20000 ug/L is used annually there is risk of aluminium accumulation in soils and resultant toxicity to plants. Aluminium is generally not an issue when soil acidity is close to neutral. Remember that the report card results are for surface waters and are not relevant to bore water and that water quality varies significantly between wet and dry seasons and between sites along the same waterway.

What can be done?

Where irrigation water has a high concentration of aluminium consider doing soil testing to confirm an aluminium problem. There are multiple forms of aluminium in the soil and most of them are not directly harmful to plants. There are also multiple methods of testing the soil for these various forms of aluminium and several different ways to use these soil test results. If elevated levels are detected talk to a specialist agronomist about the results and whether any action is required. Tips for interpreting soil test results and managing aluminium in soils can be found here.

Why is this a potential issue?

The concentration of iron in irrigation water is a potential issue when detected at levels over the threshold because it can cause reduced productivity in some crops. Most soils are naturally rich in iron and it is an essential plant micro-nutrient. Iron toxicity is caused by the reduction, under flooded conditions, of ferric iron (Fe3+) to the more soluble ferrous form (Fe2+). Ferrous iron can be absorbed by the roots, sometimes at levels sufficient to produce toxicity in the plants. Iron toxicity may involve deficiency of several other soil nutrients, especially potassium, calcium, zinc and phosphorus. Where irrigation water with an iron concentration above 10000 ug/L is used annually there is risk of iron accumulation in soils. Remember that the report card results are for surface waters and are not relevant to bore water and that water quality varies significantly between wet and dry seasons and between sites along the same waterway.

What can be done?

Where iron sensitive crops are grown on acid and water-logged soil, consider soil and water testing to evaluate iron toxicity problems. If elevated levels are detected talk to a specialist agronomist about the results and whether any action is required. A fact sheet on iron can be found here.

Why is this a potential issue?

The concentration of sodium in irrigation water is a potential issue when detected at levels over the threshold because it can cause foliar injury to crops. Sodium deposited on leaves causes foliar burn although crop species have varying sensitivity to injury from sodium in irrigation water. Irrigation water with a sodium concentration above 115 mg/L can cause foliar injury to citrus and grapes. Lucerne (230mg/L) and cotton (460mg/L) are less sensitive. In addition, the relative proportions of sodium (Na+), calcium (Ca2+) and magnesium (Mg2+) ions (sodicity) in soil can impact on productivity. A relatively high proportion of sodium degrades soil structure by breaking down clay aggregates, which makes the soil more erodible and less permeable to water, and reduces plant growth. Remember that the report card results are for surface waters and are not relevant to bore water and that water quality varies significantly between wet and dry seasons and between sites along the same waterway.

What can be done?

Where crops sensitive to sodium are grown, consider doing sodium testing on irrigation water. Damage caused by high-sodium irrigation water can be minimized by planting a less sensitive crop or by avoiding foliar contact by using furrow or drip irrigation. If elevated levels are detected talk to a specialist agronomist about the results and whether any action is required. Tips for managing sodicity in soils can be found at the NSW DPI website.

Why is this a potential issue?

The concentration of cobalt in irrigation water is a potential issue when detected at levels over the threshold because cobalt in solution has the potential to be toxic to some crops. Cobalt is not considered to be an essential plant micronutrient. In soils it is generally tightly bound however this is pH dependent and increased cobalt uptake into plants has been observed with decreasing pH. Where irrigation water with a cobalt concentration above 100 ug/L is used, production loss might occur. Remember that the report card results are for surface waters and are not relevant to bore water and that water quality varies significantly between wet and dry seasons and between sites along the same waterway.

What can be done?

The threshold in irrigation water is to protect crops from the direct effect of cobalt. Concentrations in unpolluted surface waters are generally in the order of <1µg/L so doing cobalt testing on irrigation water is generally only warranted where pollution is suspected. If elevated cobalt levels are detected talk to a specialist agronomist about the results and whether any action is required. Potential solutions may include, altering the time at which water is harvested or blending water with other available sources.