Adding nutrients through fertilizer can meet two requirements: a) a capital application that raises the plant-available pool of a nutrient in the soil to a level that does not inhibit the growth of grasses and clovers (grazing legumes). Unfortunately, this leads to increased loss of nutrients in drainage water and runoff (Figure 1.1). The amount of nutrients lost in drainage and runoff can accelerate when the sum of nutrient inputs to the farm exceeds the sum of nutrients in milk and meat plus those that are easily immobilized in the soil (i.e. the ability of the soil to retain nutrients via phosphorus fixation and the accumulation of semi-decomposed plant waste and dung as organic material in the soil).
A nutrient surplus occurs when nutrient inputs exceed losses (Figure 1.2) and the soil's ability to immobilize nutrients. Processes that cause nutrient loss, such as leaching, leaching, and immobilization of nutrients in soil, involve complex interactions.
The influence of the grazing cow on nutrient recycling in grazing systems
With a good understanding of the farming system, and soil-plant-animal processes that lead to nutrient transfer, retention and loss, it is possible for a skilled user of Overseer to prepare an audit of a farm's nutrient budget and develop a nutrient management plan that avoids excessive input of nutrients into dairy farm soils and effectively recycles nutrients within the farm, thereby reducing the impact of nutrient loss off-farm. The majority (60-90 %) of nutrients consumed by a cow in pasture and supplements (Figure 1.2 and Figure 1.3) are returned in excrement (Table 1.4), therefore the greatest movement of nutrients is controlled by the pattern of feeding and deposition of faeces and urine. Time in the paddock therefore represents 80% of the day, which results in approximately 80% of the excreta being deposited in the paddock.
The implications of the large return of N to the paddock as urine (Table 1.4) are best illustrated by considering early summer grazing events. Eighty percent of the urine and dung patches will be deposited in the paddock and 20% in the time it takes to go to the milking shed and yards (Transfer loss, Figure 1.3).
Conclusion
On average, each cow will urinate 11 times per day (or 5.5 times per grazing) and produce 12.5 dung per day (Haynes and Williams 1993). Annually, pasture rich in N (5 % N) in pieces of urine can be expected to receive about 700 kg N/ha. This equates to annual pasture growth receiving 8.4 kg of N in the area (0.012 ha) covered by urine stains from one grazing.
If a hectare of pasture is grazed 10 times per year, the urine patches will potentially generate an annual surplus of 10 x 8.7 kg N/ha. This problem of nitrogen loads in urine patches in excess of soil and pasture N requirements is a problem being addressed by current research.
SECTION 2
Introduction to Soils Used for Dairy Farming in New Zealand
- Introduction to soils
These soils are mainly formed from sedimentary rocks such as greywacke, sandstone and mudstone and are the most common soil order in NZ. These soils are mainly formed on wind-blown loess from eroded sedimentary rocks such as graywackes, sandstone and mudstone. It can be found at: https://soils.landcareresearch.co.nz/soil-data/the-lris-portal/.
Within the NZ Soils Portal, go to: https://soils.landcareresearch.co.nz/deminating-soils/nzsc/soil-order/. These soils are mainly formed on wind-blown loess of sedimentary rocks such as greywacke, sandstone and mudstone. These soils are mainly formed of sedimentary rocks such as greywacke, sandstone and mudstone.
These soils are formed primarily on alluvial and fluvial material deposited by rivers and streams that have been eroded from sedimentary rocks such as graywackes, sandstones, and mudstones.
SECTION 3
Nutrient uptake by pasture from soils
- The pasture and its nutrition
- The Form of Nutrients Taken Up by Pasture Plants
- The Role of the Soil Water
- Sources of Elements in Soils
- Factors Influencing Nutrient Retention and Plant Availability
Mineral salts in soil (and most fertilizers) are ionic compounds such as potassium nitrate (symbol KNO3). Ions separate in water because the polar nature of water molecules (positively charged hydrogen and negatively charged oxygen) acts to "pull" the ionic components apart. This thin water film of the soil connects the surface of the roots, the sink of nutrient ions, with the surfaces of the minerals and organic matter in the soil, which are the sources of the nutrient ions (Figure 3.2).
As soil water is absorbed by plant roots to replace water evaporated from leaves (Figure 3.1), nutrients are transported from the soil to the leaf. The amount of nutrient in the soil water will only supply plant growth for a few days. Uptake of nutrients by roots and dilution or displacement of the soil solution by rainfall reduces nutrient concentrations in the soil solution.
It is useful to think of soil nutrient availability in terms of its readiness to receive plants. Cation concentrations at or near the soil surface are several thousand times higher than concentrations further from the surface in the soil solution. Looking at the cation exchange model (Figure 3.5), five of the nine negative charges on the surface of the soil colloid are balanced by basic nutrient cations (Ca2+, Mg2+, K+ and Na+, called bases).
The base saturation of the soil surface can be represented as the percentage of negative cation exchange sites filled with bases. For this reason, topsoils have higher organic matter content than lower horizons in the soil profile (Figure 3.7). Most nutrient release processes from the solid phase of soil are reversible chemical and biochemical reactions.
Major Factors Affecting Nutrient Retention and Plant Availability
SECTION 4
- Introduction to Fertiliser Materials
- Basic Introduction to Fertiliser Materials
- Common Nitrogen Fertilisers
- Common Phosphorus Fertilisers
- Common Potassium Fertilisers
- Common Sulphur Fertilisers
List the common nitrogen, phosphorus, potassium and sulfur fertilizers used on pasture in New Zealand. Fertilizer quality - the percentage of nutrients per unit of dry weight The New Zealand Convention. In New Zealand, there is a standard terminology used to refer to fertilizer quality (nutrient content of fertilizers).
The fertilizer and its quality can be registered with the New Zealand Fertilizer Quality Council. Fertmark is an independently reviewed fertilizer quality assurance program organized by the New Zealand Federated Farmers Union. However, in some countries (e.g. USA), the P and K contents of fertilizers are expressed in terms of their oxide content (P2O5 and K2O) rather than the elemental composition.
It is often the case with fertilizing materials that the multi-nutrient requirements of crops or pastures per hectare cannot be exactly met using conventional fertilizers. More information on how to calculate the plant-available nutrient content of manure is presented in the higher level courses. The choice depends on the most suitable fertilizer for the soil, climate, topography, farm condition, other nutrients present in the fertilizer, and the cost of the fertilizer per unit weight of nutrient.
The following example illustrates the difference in cost of two nitrogen fertilizers, urea and ammonium sulfate, to provide one weight unit of nitrogen. When two fertilizers with different particle size ranges are mixed, segregation of the two fertilizers will occur in the mixture. List fertilizer materials that can be used to make a safe, spreadable mixture that will provide N, P, K, S for rapid delivery to the seedbed soils.
SECTION 5
- Introduction to Soil Physical Properties
- Soil Texture What is soil texture?
- Soil Structure What is soil structure?
- Soil Water
Consistency is the resistance to deformation or splitting, and is dependent on the water content of the soil i.e. It is clear that it is important that farmers limit cultivation to periods when the soil is less than (ie drier) than the plastic limit. These large aggregates expand and fit very tightly together when the soil is wet and impermeable to water.
Susceptibility to crust formation on the soil surface (caused by: raindrops, machinery, animals). In soil micropores, water movement is so slow that it is negligible. Field capacity is somewhat imprecisely defined as the water content of the soil after excess water drains off.
If the soil dries out to the point where the roots cannot draw water at the rate required by the leaves, the stomata will close and the plant will be "stressed". PWP is the soil water content when plants have absorbed all the water they are capable of taking from the soil. When the soil is saturated, the rate of movement of water through it is determined by the saturated hydraulic conductivity.
The soil therefore takes center stage in most schematic diagrams of the hydrological cycle – see Figure 5.3 for an example. Often the major pathway for water to move out of the soil is plant uptake and evaporation (sometimes called evapotranspiration). Unless the soil is drier than stress point, for vegetation-covered soil it is the available energy supply that determines the rate of evaporation.
It is possible to trace quantitatively the major daily inputs and outputs of water to and from the soil using the soil water balance equation. Also, because plant competition for nitrate uptake is high and soils do not have the ability to retain nitrate (the form of N most commonly taken up by pasture plants) and is easily lost as water percolates through the soil.
Multi-choice Self-Assessment
C As anions and cations dissolved in soil water D As charged ions dissolved in soil water. Choose the correct statements about the main role of essential elements A Nitrogen is required for plants to build protein and chlorophyll B Magnesium is involved in cell wall construction. A NO3- Fe and Al oxides on soil particle surfaces B H2PO4-, HPO42- Fe and Al oxides on soil particle surfaces C K+,Ca2+ Organic matter and clay surfaces.
A Contains 9 kg of nitrogen and 12 kg of sulfur per 100 kg of fertilizer B Contains 9 kg of phosphorus and 12 kg of sulfur per 100 kg of fertilizer C Contains 9 kg of phosphorus and 12 kg of sulfur per ton of fertilizer D is DAP. Potential evaporation in central New Zealand is typically between 0 and 10 mm per day in July. In a region of New Zealand with 150mm of rainfall in July, the July drainage will take place every July.
B Drainage will be greater than 50 mm each July C Drainage will be greater than 500 mm each July D Drainage will be less than 50 mm each July.
Multichoice Self-Assessment Answer score sheet
