It has become very clear to me that the amount of NPK (nitrogen, phosphorus, potassium) we put on our crops isn’t indicative of what the plants need or can even begin to utilize.
We know that nitrogen is key to production of new cells, new enzymes and green pigments and to leaf and stem growth. Phosphorus encourages root growth and blooming and plays an essential role in promoting photosynthesis. Finally, potassium helps with water uptake and the development of flowers and fruit and helps mitigate plant disease.
A typical soil is supposed to be 25% air, 25% water, 45% minerals and 5% soil organic matter. However, the 5% figure is misleading. While the soil organic matter often makes up less than 5% of the soil by weight, it controls 90% of soil functions essential for plant growth. Some 95% of the nitrogen and over 50% of the phosphorus in the soil is contained in the soil organic matter. If your organic matter is hovering around 1-2%, most of your nitrogen and phosphorus applications are not being mineralized by the microbial community and made available to the plants. The soil is simply a sieve for these nutrients and they’re “just passing through.”
Here’s another fact: Between 19% and 54% of the soil’s cation exchange capacity (the ability of the soil to hold onto plant nutrients) is due to soil organic matter. Soil colloids — composed of clay and organic matter — are negatively charged particles. Negative attracts positive. This means that that they will attract and store cations, however they will repel negatively charged anions like nitrate, sulfur and boron. The humus in organic matter has charged sites that will attract and store anions like nitrate. This is why nitrates are readily leached from soils with low levels of organic matter.
One of the great paradoxes of farming is that lack of nitrogen is regarded as one of the great limitations on plant growth, and yet plants are bathed in it as our atmosphere is 78 percent nitrogen. Microbes bring nitrogen from the air into the soil and convert it into other forms — nitrate, ammonia, ammonium and amino acids — for plants to utilize it. Again, organic matter is the primary source for plant nitrogen and the buffer and storehouse of all the minerals that plants need such as calcium, magnesium, zinc, potassium, phosphorus, and others.
The bottom line is that you can put nitrogen and other macro nutrients onto your fields until your heart is content, but unless your soil can hold it and process it via a robust soil biology profile, you’re wasting money and are off track as you should be concentrating on building soil biology and increased soil organic matter. Effective farm management with a focus on soil biology will mean that farms can get considerably more crop-available nitrogen for free and can substantially reduce the amount of nitrogen applied, given the extreme waste taking place.
Finally, a high percentage of the nitrogen in soil organic matter is in amino acid form. Amino acids are some of the most important building blocks of life because they are the basis of DNA, RNA, proteins, hormones and are integral to many vital functions. Plants generally synthesize the amino acids that they need by combining the nitrate form of nitrogen with the glucose sugar that they form through photosynthesis. This is why nitrate is so important. Our oceanic fish hydrolysate, Pacific Gro, has a very high amino acid profile and represents a good starting place for any grower to build better soils.