Fertilizer Timing and Nutrient Cycling Protocols

Most nutrition recommendations are expressed in pounds of phosphate or potash per acre; fertilizers come in various forms including granular, liquid, or gaseous formulations.

Granulated fertilizers are solid mixtures designed to remain unbroken when being handled and spread, providing uniform application of nutrients. Liquid fertilizers may contain anhydrous ammonia, which requires special handling considerations.

Fertilizer Timing

Delivering fertilizer at the appropriate time and place is one of the key components of effective nutrient management. This involves understanding soil test results, regional climate conditions and grass type considerations among other things.

Timing fertilizers must also follow sound principles to avoid over-fertilization, and this can be accomplished by maintaining records of field maps, sample locations and dates; fertilization history; planting history; tillage practices used; as well as soil test results over time.

As a general guideline, use nitrogen (N) fertilizer only when indicated by soil testing results. A calculator or spreadsheet is typically necessary to ascertain the number of pounds of N present in any application since different fertilizers contain various amounts.

Research has produced simple N supply calculators such as those found in the UK’s RB209 fertilizer recommendations system and decision supports such as SUNDIAL model (Smith et al. 1996). However, to improve these tools and create new ones effectively, a deeper knowledge of nutrient cycling processes must be gained in order to enhance them or develop them further.

Nutrient Cycling

The nutrient cycle is nature’s system for recycling essential nutrients for use by living and nonliving things alike. It involves carbon, hydrogen, oxygen, nitrogen and phosphorus moving between organic matter forms as well as between living things; its speed depends on several physical and biotic factors which determine their release, transport and capture by soil microbes.

Nutrients are carried to plants via water, air and soil microbes in an intricate system which is determined by temperature, humidity and other environmental variables. Chemical and physical processes in soil influence mineral solubility, cation exchange capacity, solution pH level and binding with soil particle surfaces – factors which ultimately determine their availability to plants. Understanding how such factors influence availability is paramount to designing fertilizer formulations that will be efficiently taken up by plants.

Organic matter in soil serves as an interactive platform where beneficial fungi and bacteria thrive, secreting enzymes to break down complex organic material into nutrients which reach plant roots via their rhizosphere. This microbe-rich environment directly impacts plant health while increasing resistance against pathogens.

Forest ecosystems change over time as they mature and change; as this happens, elements like carbon (C), nitrogen (N) and phosphorus (P) become dispersed differently between organic and mineral soil layers – having major implications for long-term sustainability of forests.

Nutrient cycling models provide a framework for evaluating the effect of management practices on forest nutrient status, with predictions made at both stand level or forest canopy scale for export and import of nutrients. These models combine observations and predictions about soil nutrient transport, litter production and microbial activity to estimate fluxes of nutrients in soil, litter production and microbial activity in order to assess how closely their predictions match observed fluxes in the field. Predictions can then be compared with observed fluxes to evaluate how accurately this model matches field data. Nutrient cycling models can also be used to measure tree species’ uptake efficiency of nutrients and identify opportunities for improving NUE through fertilization or adding N-fixing species. Finally, climate change may have an impact on forest ecosystems’ nutrient cycles as well.

Fertilizer Rates

Finding an optimal fertilizer rate for each crop field requires evaluating several variables at a nanolevel, including crop nutrient uptake rates; soil chemical, physical and biological properties; weather; water composition; testing methods and research data as well as understanding interactions among fertilizer, crops, practices and equipment.

Reconciling crop needs with rate of application is vital for optimizing yields and mitigating environmental risks. Fields may have differing needs in terms of major nutrients like nitrogen (N), phosphorus (P2O5) and potassium (K2O) due to differences between soil types, test levels, crop varieties and range. Grid sampling and variable rate fertilization allow farmers to match these site-specific nutrient levels with their crops’ specific requirements.

General guidelines suggest limiting N application rates in Mississippi to no more than 1.3 pounds per bushel of realistic yield goal for most crop species, to prevent an excessive use that increases greenhouse gas emissions. Excessive fertilization with N can lead to nitrification and denitrification reactions which produce N2O and NOx emissions that contribute significantly to global warming; excessive phosphate (P) application can buildup in soil layers leading to release of PO4-P into the environment.

Maintaining accurate records of nutrient applications, agronomic practices and soil characterization is of great significance in order to monitor crop nutrient supply and track movement of nutrients in the soil. Records should be kept for at least three growing seasons so that recommendations based on actual uptake rather than initial fertilizer recommendations can be provided.

Container labeled growing media rates are designed for open air cultivation, not taking into account the closer rooting that occurs in facility soils. Therefore, growers must use higher growing media rates when using facility soils. It is also wise to blend fertilizers when selecting an appropriate rate; this ensures nutrient concentration remains consistent throughout and reduces chances of over or under applying an application rate.

Equipment

Ecological agriculture prioritizes increasing nutrient efficiency in soils as a core goal, which can be summarized as optimizing plant nutrition without over-supplying. To do so efficiently requires careful management of both SOM and its living component SMB; including energy conservation in tillage practices; improving soil structure through improved tillage techniques and cycling of nutrients such as nitrogen through nitrification, denitrification, or other biologically-mediated processes; as well as avoiding losses to surface water bodies from landscape sources.

Soil testing and fertilizer application should be as precise and accurate as possible for maximum production, investment return and environmental quality. This is especially crucial for fields growing multiple crops with differing nutritional needs or rotation schedules; representative sampling helps ensure test results can be understood correctly so as to best manage rates, timing and placement. Automated metering equipment that calibrates specifically to specific parameters like porosity, moisture content or organic matter content greatly enhances soil testing accuracy.

Consider factors like ease of handling and application, safety concerns and storage options when selecting fertilizer application equipment. Anhydrous ammonia must be stored and handled under very specific conditions in order to prevent accidental exposure to its by-product when it dissolves in water; to be used safely it must be injected under ground or controlled storage restrictions apply – these varies by state and federal regulation.

Nutrient audits or budgets can provide invaluable insight into the inputs and outputs of N, P and K on individual farm fields or entire farms systems. Such analyses can reveal whether nutrients are being exported out of production sites to cities for urban consumption, depleting limited stockpiles of these important nutrients while increasing surpluses; or whether large amounts are being recycled back onto the farm through crop rotation, manure application or soil mining by microbes.

Research efforts are currently focused on ways to enhance nutrient cycling, from developing decision supports like the UK’s PLANET system nitrate calculators and soil sensors to developing mechanistic models of cycling through SOM and SMB that include microbial processes relating to nitrification and denitrification processes; stable isotopes have also become an effective means of tracking fluxes in this regard.