The Importance of Fertilizer Management for Small Farmers
Soil fertility is a key for high yielding crops and reducing economic pressure for small farmers.
Nutrient management is key to having a sustainable high yielding crop, without damaging the plant, environment, and overall soil productivity. Even if the operation is organic or conventional; the crop’s nutrient needs must be met to ensure a satisfactory yield. One vast challenge for small farms is the multiple cropping systems they implement. Most small farms are focused on specialized markets with numerous crops and multiple crop management practices, which required various fertilizer needs not seen with large monoculture farming operations. In most situations, small farms don’t have the luxury of buying bulk fertilizer blends or bulk liquid fertilizer at discounted rates because most small farms have very few acres in crop production and these acres can be divided into multiple crops. This leads to small farmers paying more for their fertilizer, with numerous fertilizer batches for each unique cropping system, and a higher chance of over and under applying fertilizers when meeting crop fertility needs.
Strawberries in bloom under plasticulture in North Carolina.
Courtesy of Aaron D. Pettit
Fertilizers applied to meet crop needs should be based on soil fertility test, plant tissue nutrient test, and/or researched crop yields. Materials applied as fertilizer or added as a supplemental nutrient source, should have a known nutrient value, or have a known researched crop nutrient value like seen frequently in green manures (plants used for retaining nutrients or fixing nitrogen). This can be hard for small farmers, especially farms with multiple crops, various organic soil amendment/nutrient sources, and multiple fertilizers, with very little room for error. Small farmers often using livestock operation waste (manure) or other organic materials, as a source of fertilizer and/or soil amendment. Quite often these materials are applied to cropland without knowing the nutrient values associated with the material. Also, these organic materials can have fluctuations in nutrient content depending on multiple factors. Take for example cow manure, nutrient value of that manure will change with season, animal supplemental feed source, grazing material, feed storage, manure storage, and location grazed (soil, cover, geography); this can lead to nutrient values fluctuating, not seen in commercial fertilizers because they are required by law to ensure the product is tested and is sold in accordance with labeled nutrient values. Applying nutrients sources with unknown nutrient levels should be avoided and any possible nutrient source should be accounted for in meeting crop nutrient needs. Farmers should test their manure or other soil amendments/possible nutrient source, if there are no test results for the specific product, to ensure applied material is calculated into the crop nutrient needs. Most states and a lot of private agriculture labs run waste analysis for such materials.
Different crops will have different fertilizer needs; for example, trellis tomato versus kale; fruiting crops in general will need additional nutrients, such as Nitrogen (N), Phosphorus (P), Potassium (K), Calcium (Ca), Boron (B), etc. With a portion of the annual fertilizer application having a beneficial impact if applied during flowering and fruit development stages. Applying appropriate amounts of fertilizer at proper times, lead to beneficial impacts, such as, high yield, proper fruit formation, and reduction in disease/pest pressure. Applying improper fertilizer, too much or too little, at incorrect times of the year can lead to negative impacts, such as, lower yields, irregular fruit formation, increase in disease/pest pressure, nutrient loss, element toxic soil and reducing land use, and environment impacts from excessive nutrient runoff and leaching. A past example, a strawberry grower, under plasticulture, is adding nitrogen (N) at 120 lbs. per acre seasonal, with a synthetic fertilizer, in accordance with crop needs and soil test results; 60 lbs. of which was applied at planting and the rest applied as liquid through the drip during flower and fruit development. However, the farmer also applied manure from his animal operation to the field before planting but did not reduce his fertilizer application for the extra nutrients associated with the manure. This had a negative impact to his crop; causing greater disease and pest pressure, increase vegetation growth, reduction in fruit yield, and poor fruit quality (taste and shelf life), leading to increase cost for pest and disease control, poor customer satisfaction, and reduction in revenue. The manure application should have been tested for nutrient values and applied in accordance to meet crop needs as a pre-plant fertilizer, reducing or eliminating the synthetic pre-plant fertilizer, which would have decreased the cost to the farming operation. The situation could have been worse, with improper application of some waste products over long extended periods, leading to soil buildup of metals and other compounds in the soil that have the capacity to become toxic for specific crops, leading to reduce usage for the soil and poor productivity. With other environmental impacts, of over applying fertilizer materials, resulting in nutrient loss from runoff and leaching, leading to environmental issues. The environment damage can have permanent or long-lasting effect causing damage that effect water quality and wildlife, causing impairment to drinking water as well.
Boron deficiency symptoms in tomato fruit.
Nutrient needs for the crop can change as plants mature and production of fruit occurs. Particularly during fruit set with prolong fruiting over an extended time and/or heavy fruit loads, nutrient deficiencies can be noted, even under normal fertilization. With crop production limited by the most limited nutrient available for plant uptake; called Liebig’s law of the minimum. This can easily be seen in multiple crops under different growing conditions. A past example is a greenhouse tomato grower. His crop always starts great with a heavy production of tomatoes followed by sharp decrease in tomato production with deformed fruit development and fruit drop occurring. The farmer was using a standard greenhouse tomato fertilizer in a stock tank with the second stock tank for Epsom salt (MgSO4) and other supplement fertilizers; he was applying it in accordance with the label and published nutrient solution requirements for greenhouse tomato production. However, the greenhouse tomato plants were producing such a heavy fruit load, boron (B) became deficient for new developing mid-season fruit, which led to the noted symptoms. This was evident through the visual plant symptoms and plant tissue test results, however nutrient solution test results showed adequate B levels at 2 ppm B (recommended range of 1 to 2 ppm B for greenhouse tomatoes). Even though boron was sufficient in the nutrient solution, increasing the B by 1 part per million (ppm) to a total of roughly 3 ppm B resulted in the farmer having a higher yielding crop over a longer duration. Sometimes crop needs can vary, even beyond crop recommendations. This farmer was happy to resolve the fruiting issue which had plagued him for multiple years but was not sure why it was happening.
Small Farmer should take advantage of resources, such as soil, waste, and plant tissue testing. Apply fertilizer according to the needs of the crop and soil. Avoid improper fertilizing to reduce damage to the crop, soil, and environment. Use public (University, State, or etc.) and private (consultant) resources to help calculate fertilizer requirements and use of waste materials, if unsure. It is always a good practice to have a nutrient management plan and keep good records of past applications (fertilizer types, nutrient values, application rates, and test results). Most specialist will ask for these records, if called upon to help. Lastly, it’s sometime helpful to get a second opinion on fertilizer requirements and applications. This is also true when purchasing fertilizer or getting advice from a consultant (fertilizer sale rep) that makes money from sales. Plant nutrient deficiency symptoms can be result of environmental factors, such as climate, soil properties, soil water, terrain, etc. and fertilizer will only sometimes temporarily solve the problem. I have seen farmer spend way too much money from getting incorrect advice or guidance.
Aaron D. Pettit is a private soil consultant at Aaron Soil/Plant Consulting, as well as a federal employee for USDA. Aaron enjoys working in the field of agriculture, through research, farming, and with local grower to tackle problems within the industry.
