Phosphate and Organic Fertilization

In the early 1800s, it was learned that phosphorus promotes growth in plants and animals. At first, bones, which contain the element phosphorus, were used as an agricultural fertilizer. Today, phosphate rock provides the phosphorus element of the nitrogen-phosphorus-potassium mix that fertilizer provides for plants. 

Phosphate rock was first mined in England in 1847 for use as a fertilizer. It was in 1881 that civil engineer J. Francis LeBaron, a civilian employee of the Army Corps of Engineers, discovered Florida’s treasure in black phosphate pebbles in the Peace River. A “hard rock” phosphate district in north central Florida was discovered next. Thus began Florida’s phosphate mining industry. Florida’s phosphate mining today accounts for about 75% of the phosphate used in the United States, as well as about 25% of the phosphate used around the world.

Soils need phosphate and other nutrients. When farmers apply nutrients, either in organic or mineral form, it is to fertilize the soil, not the plant. The soil then acts as a conversion system for the crops, receiving, storing, transforming, transporting and exchanging plant nutrients. A fertilizer formula, targeted towards the needs of a specific crop, may not reach the plant in the desired proportions. The original composition may be modified, prior to the uptake by roots, through adsorption, fixation, leaching, volatilization, and reduction, all processes that are governed by a combination of the chemical, physical and biological properties that characterize different soil groups.

The key to growing crops that are plentiful and that contain the nutrients we need is to assure that the local soil has the nutrients it needs.

Manure and compost, for example, typically have and provide relatively low nutrient content in comparison to commercial fertilizer. If enough is spread, it may provide adequate nitrogen, but likely will not provide enough phosphate. 

Where animal and crop production are integrated on a farm where organic farming is employed, manure or compost can be hauled daily to the fields or be stored until soil conditions are suitable to apply them. This practice can provide organic matter and plant nutrients for the small or specialized farm, if it is used in conjunction with an organic phosphate source such as bone meal.

It is, however, more expensive and labor-intensive to collect, handle, store, transport and spread enough manure or compost to fertilize a large-scale agricultural field and provide other nutrient supplements. Meanwhile, too much manure or compost in one location will increase the likelihood of polluting the groundwater with the nitrates and/or pathogens borne by the materials.

Mineral fertilizers are needed to maintain the level of soil fertility needed to meet the nutritional needs of the world’s population.

The question is not if organic fertilization techniques can provide the phosphate and other nutrients crops need. The question is whether organic fertilization techniques can sustain the crop yield needed to produce enough food to feed the world’s present and future population.

Organic farming techniques recycle the nutrients in plants and animal waste products by various crop management techniques such as planting a cover crop and plowing it back into the field to provide nutrients. Such techniques can produce healthy crops if soils are not seriously nutrient-deficient. The problem is finding a market willing and able to pay the relatively high price the produce must bring to offset the high cost of production using organic farming methods.

To feed the world’s population, however, organic farming is not economically or environmentally practical. There is an ongoing discussion on the matter worldwide in the agricultural community, and agronomy and soil experts agree that the use of fertilizers, both inorganic and organic, needs to be tailored to local soil needs. Soil testing and other diagnostic tools should be used. If the nutrients in the soil are already sufficient, adding fertilizers is more likely to damage the environment and be economically wasteful.

Soils, however, that are severely nutrient-deficient due to clear-cutting forests, slash and burn farming, intensive farming, highly weathered soils, erosion and other factors cannot be restored with organic farming.

It should be remembered that in America’s early days, one of the reasons people moved west was to find more fertile farmland after the nutrients in the eastern fields were exhausted. At that time, mineral fertilizers did not exist to supplement natural and managed recycling to replace the soil’s nutrient losses.

Consider the following excerpt from “Long-Range Perspectives on Inorganic Fertilizers in Global Agriculture,” a paper presented at the International Fertilizer Development Center (IFDC) 1999 Travis P. Hignett lecture, November 1999, by Dr. Vaclav Smil, University Distinguished Professor, University of Manitoba (Canada).

“In 1900 the virtually fertilizer-free agriculture was able to sustain 1.625 billion people by a combination of extensive cultivation and organic farming on the total of about 850 million hectares of land,” Professor Smil said. “The same combination of agronomic practices extended to today’s 1.5 billion hectares of cropland would feed about 2.9 billion people (or 3.2 billion after adding food from grazing and fisheries).

“This means that without nitrogen fertilizers no more than 53% of today’s population could be fed at a generally adequate per capita level of 1900 diets. If we were to provide today’s average per capita food supply with the 1900 level of agricultural productivity, we could feed only about 2.4 billion people, which is about 40 percent of today’s total.”

Farming techniques and equipment have progressed since 1900, but organic farming still relies on a practice that is less efficient than producing and utilizing commercial fertilization techniques.

Professor Smil also said the way to lower the global dependence on nitrogen fertilizer would be for the world’s population to share the distribution of food and restrain the amount of protein people demand.

“In such a world, he said, “the populations of affluent countries would have to reduce their meat consumption since hundreds of millions of people would have to revert to simpler diets containing more cereals and legumes. Realistic chances of this dietary transformation, running directly against the long-term trend of global nutritional transitions, are extremely slim, but even in such an altruistic and frugal world, ammonia synthesis would still have to supply at least one-third of all nitrogen assimilated by the global food harvest!”

Professor Smil uses the term “ammonia synthesis,” which is the basic process of nitrogen mineral fertilizer production.