Nutrient Management

Important!

When selecting "Crop-independent", the caclulator will determine N availability from soil at optimal moisture without calculating crop N uptake and fertilizer need. This option is not intended for unirrigated summer fallow fields. Planting and harvest dates need to be entered, as they will be used as the start and end date of the simulation.

Important!

The harvest date should reflect the date a crop is ready for harvest. The actual harvest date may differ, for example when harvest equipment is not available.
In the case of a crop-independent simulation, the harvest date is the end of the simulation period.

Important!

The harvest date should reflect the date a crop is ready for harvest. The actual harvest date may differ, for example when harvest equipment is not available.
In the case of a crop-independent simulation, the harvest date is the end of the simulation period.

Important!

Yield should be entered as measured at harvest. For example, silage corn yield is commonly expressed at 70% moisture, tomato yield is fresh weight.

Important!

Soil samles for residual nitrate analysis shold be collected pre-plant in spring. Values based on samples takein in fall are not accurate, as soil nitrate values can change considerably during the winter.
Not testing for soil nitrate or leaving these fields blank may cause the fertilizer N requirement to be overestimated.

Important!

Furrow irrigation: only the furrows between the beds are filled with water.
Flood irrigation: the entire surface of the soil is covered by water.

Important!

Fertilizer applied before or at planting either as dry or liquid fertilizer can be entered here.
Urea (46-0-0) and MAP (11-52-0) are entered as lb/ac of material.

How to select your soil type?

The soil type is used to calculate N mineralization. For this calculator,
if the clay content is less than 15%, select sandy;
if it is 15-35%, select loamy;
if it is above 35%, select clayey.
Organic soils include those typically found in the Delta and Tulelake Basin.

Nitrogen Uptake and Applications

Nitrogen from soil and water includes residual nitrate, N mineralized during the growing season and N applied with irrigation water.

The graph and the calculations are based on average values from commercial fields in California. Weather conditions, management and variety selection all can affect N uptake and availability. It is therefore important to monitor the N status of the field during the season with soil or leaf analyses. More information about soil and leaf sampling can be found here.

Nitrogen Budget

Estimated N uptake:

In-season N mineralization:

Available residual nitrate:

Nitrate in irrigation water:

Preplant/starter N available:

Assumed fertilizer N use efficiency:

In-season fertilizer N needed: