Soil Nutrients and Management

• Nitrogen (N)
• Phosphorus (P)
• Potassium (K)

 Soil pH

• Effect of acidity-alkalinity to nutrient availability in the soils
• Amendment for soil acidity

 Soil testing for NPK

• Steps employed in rapid test of N-P-K                                    
• Things to remember when use soil test kit 15

 Steps in use of soil test kit

–     Soil sample preparation and N-P-K extraction from soils

–     Ammonium measurement procedure

–     Nitrate measurement procedure

–     Phosphorus measurement procedure

–     Potassium measurement procedure

–     Testing soil pH

SOIL NUTRIENTS AND MANAGEMENT

Of the 16 essential nutrient elements for plant growth, 13 are derived from mineral constituents of most soils.  Continuous cultivation of plants over long periods or many seasons may result in deficiency of nutrients to plants.  Six elements are essential to plant growth and development and are required in larger quantities compared to the others.  The six include N,  P,  K, Ca,  Mg and S.  Generally, nitrogen, phosphorous and potassium contents in the soils are low while calcium, magnesium and sulfur are normally sufficient.

Nitrogen (N) is the only element that is not a component of rocks and minerals.  Nitrogen sources, ammonia and nitrates, in soils are decomposition products of soil organic matter by soil micro-organisms.  The NH₄ and NO₃ ions are the chemical forms available for plant use.  Nitrogen is an essential component of protein along with other organic compounds vital for plant development and growth.  It is also an essential component of chlorophyll.   Plants with sufficient nitrogen will typically have greener leaves, grow fast and have higher yields.

Management on Nitrogen Shortage

When nitrogen shortage occurs, the plant will grow slowly and exhibit yellowing leaves, stunted growth, late-flowering and low-production.  The prescription of such symptoms is to apply fertilizer to the plant with
N-fertilizer.  Nitrogen fertilization can be from either organic or inorganic sources.  In the case of organic fertilizers, it must be incorporated in the soils in advance of planting in order to allow time for decomposition and release of nitrogen.  Inorganic fertilizers, such as ammonium sulfate or urea that contain high levels of nitrogen should be used in relatively smaller amounts for each application but frequently applied.  It should be applied at the first sign of nitrogen shortage.  Analysis of nitrogen in the laboratory often includes soil organic matter.  In the case of analysis in the field, the levels of ammonium or nitrate may be assessed instead.  The application of nitrogen fertilizer should be considered when medium to low levels of ammonium or nitrate are detected in the field.

^1/   There are several kinds of liming material used as soil amendments.   The values in Table3, shows the recommended quantities of finely-ground lime in kg/ha. In case other kinds of liming material are used, the following numerical values are to be employed in calculating the quantity of lime to add.

1. numbers in the table x 0.74 = kg/ha (CaCO₃)
2. numbers in the table x 0.56 = kg/ha (CaO)
3. numbers in the table x 0.92 = kg/ha (Ca, Mg (CO₃)₂)
4. numbers in the table x 1.25 = kg/ha (Marl soil)

SOIL TEST KIT PURPOSED AND CERTIFICATED

iG9 Soil Test kit is hand-carried kit that permits quick tests for soil pH as well as the key plant nutrients in soils: Nitrogen (nitrate and ammonium), Phosphorus and Potassium. The results can be read in 20 minutes in the field. One kit can analyze 50 soil samples resulting in 250 individual analyses.

Site-specific Nutrient Management

Modern agriculture must meet the multiple challenges of increased productivity to meet food needs of larger populations, profits to ensure food and welfare security and be more environmentally healthy. One way to meet such challenges are to apply concepts of site specific nutrient management. It has been well recognized that the application of adequate quantities of plant nutrients is a key to increasing maize productivity, economic return, and to reduce negative environment impact.