Be Your Own Crop Doctor
Many growers may have probably called for some technical assistance of an expert at some point. Whether its, low seedling emergence, incidence of unfamiliar diseases, serious insect pest attacks, unusual plant appearances, it’s always best to consult a plant doctor or agronomist. But what if they can’t come on time? What if your area is so remote or inaccessible? What if you need an answer now and not later?
Of course, having a Pioneer agronomist to troubleshoot for you is good, but being personally familiar with problems developing in your field is a lot better. Checking the field regularly and identifying problems is an important part of crop management. In short, you can be your own plant doctor.
One of the common problems in the field is nutrient deficiency. Crops have a way of expressing malnutrition and each symptom is specific to a particular nutrient element. These symptoms indicate that there is a need that is not being met. If problems are detected early, solutions can be formulated such as sidedressing. In case they cannot be corrected this year, it can be of help in planning fertilizer programs for the next season.
A healthy plant produces rich, dark green leaves and this is an indication of a high level of chlorophyll. These green leaves are essential in the optimum trapping of the sun’s energy and in the production of sugars required for plant growth and development. With healthy leaves from healthy plants, a bountiful harvest of good quality ears and grains can be ensured. Any alteration in the leaves’ appearance and even ear formation could only mean nutrient shortage or stress factor.
For this issue, our main discussion will evolve on the three major nutrient elements required for crop production: nitrogen (N), phosphorus (P), and potassium (K).
Nitrogen (N) deficiencies are less likely to be detected in the very early growth stages. However, yellowish young plants can easily be attributed to N shortage. Sidedressing N fertilizer can solve the problem. At the knee high stage, expect a very rapid growth rate and demand for N doubles. If N is not enough, the tip of lower (older) leaves begin to turn yellow and progresses along the midrib. Because N is a mobile nutrient, the hunger signs move up to leaves in the higher parts of the plant while the lower leaves die out.
Premature death of the plant and small, chaffy ears result from N deficiency.
Nitrogen hunger sign is yellowing that starts at tip and moves along middle of leaf.
Nitrogen is essential throughout the growing season. If plant runs out of N at a critical time, ears are small and protein content is low. Kernels at tip do not fill.
When the leaves of corn seedlings have reddish-purple coloration, there’s a very big chance it is due to phosphorus (P) deficiency. It could also be due to genetic sensitivity to cold weather or physical restriction to root development). Other indications of P deficiency include weak and spindly stalks either with barren or small, twisted ears. Delay in crop maturity can also result from P deficiency.
Phosphorus (phosphate) shortage marks leaves with reddish-purple, particularly on young plants.
Phosphorus (phosphate) shortages interfere with pollination and kernel fill. Ears are small, often twisted and with undeveloped kernels.
The initial symptom of potassium (K) deficiency is the yellowing or browning of the margins of the lower leaves. The discoloration will then move gradually toward the midrib and up to the leaves in the higher part of the plant. Potassium-deficient corn plant also has a dark-brown discoloration of the nodes which can be revealed by slicing the stalk lengthwise (see illustrations). Tip filling (or grain-filling at the ear tips) will also be problematic and ears may develop chaffy kernels.
Drought effects will also be pronounced when K supplies are insufficient since it is a major factor in water use efficiency.
POTASSIUM (potash) deficiency appears as a firing or drying along the tips and edges of lowest leaves.
POTASSIUM (potash) shortage shows up in cobs with poorly filled tips and loose, chaffy kernels.
OTHER NUTRIENT DEFICIENCIES
While N, P, and K are very important for corn production, other essential nutrients can also be important factors which may help or limit the achievement of optimum yield. Their observed deficiencies in the field, however, occur less frequently. Below are brief descriptions of some of the other nutrient deficiencies in the cornfield which can help guide you in troubleshooting your problem”.
BE AN EFFECTIVE PLANT DOCTOR
Soil acidity is an important thing to keep in mind whenever nutrient management is being tackled. As you know, acid soils with very low pH of < 5.5 can cause deficiencies even when adequate supplies of nutrients have been applied. In this case, it is very important that soil tests or evaluation is done on a regular basis to identify pH problems and monitor soil P and K levels. Liming can help correct acidic soils.
As a corn doctor, evaluate your ‘patient’ with thoroughness. Take note of the general appearance of the abnormality and compare it with the `normal’ healthy areas. Get your sample plants from the normal and problem areas. Look at the roots and inspect the stalks and ears. Also, look for possible pest problems such as insects and diseases. All these can provide useful diagnostic information (through laboratory analysis) that could spell a modest result for use in the current season and more profitable result in the next growing season.
The following are additional tips:
1. Note what you saw and identify the exact location in the field.
2. Make a good documentation of the problem by taking pictures or video and provide adequate description (location, dates, field conditions, etc).
3. At harvest time, go out and check ears for poor grain-filling, deformed ears, and barren stalks because these may suggest nutrient shortages. Collect soil samples from the problem areas and `normal’ areas. Comparing lab analyses of these samples will complete the diagnosis.
RESPONSIBLE CROP MANAGEMENT
Learning more about your corn is an important part of responsible corn management. It is always best that all growers strive to go beyond the operational details of corn production and lessen their dependence on technical assistance from government or private agricultural technicians. Proper fertilization, based on soil tests, coupled with other sound management practices is key to efficient and productive
Nutrient Deficiency Symptoms
Sulphur (S) Light green coloration in upper leaves and poor growth rates.
Magnesium (Mg) Whitish striping along the veins of the lower leaves with
some purplish discoloration along the leaf margins.
Copper (Cu) Drying and twisting of the upper leaves.
Zinc (Zn) Chlorotic stripes parallel to the midrib of young leaves,
shortened internodes, and stunted plants.
Boron (B) Barren stalks or barren ears in well-fertilized, high population fields.