Soil Testing For Sweet Corn Cultivation

Importance of Soil Testing

Give some examples of soil tests (and the results) you’ve done. What actions were taken as a result of the tests?

Initially, before planning the garden, the soil should be tested which assess how much the soil is suitable for planting specific plants which are required to be planted. Therefore, before preparing the soil for horticulture, the soil would be taken to the laboratory and would be tested against the current requirement. For sweet corn cultivation, the necessary soil tests that would be carried out are described below:

The soil structure and tilth test is important for growing sweet corn because it grows well in sandy or well-drained soil. Soil in a neither wet nor dry condition has been taken up and then the soil is broken by the fingers. Organic rich soil forms almost round aggregates. This shows that the ground is porous. Porous soil allows free water and air movement, which is suitable for sweet corn production. The results revealed that the soil had good structure and tilth.

This test is done for analyzing the presence of organic plant residue from the previous plowing. The soil would be dug up to 6 inches and the presence of brown colored humus would be observed. Presence of organic residue indicates good aeration and decomposition in the soil which is good for cultivation of sweet corn. The result revealed that compaction of the porous soil is suitable for cultivation of sweet corn.          

It is done for analyzing the suitability of the soil for cultivation. The amount of fuel cost during tilling, digging. The effort that has to be given for the cultivation of plants also determines the workability of the soil. The more workable the soil is, the more its yield. The soil which is being used is an aged soil where one crop has already been cultivated in previous session. The previous reports supported the good yield of the crop field.

It is tested for analyzing the depth of the soil which is accessible for the plant that is to be cultivated. In this context, the compaction should be at least 6 inches for cultivating sweet corn plant. For testing, a wire is inserted in the soil and the depth of wire insertion has been noted. A very compact soil is not ideal for growing plants. These soils inhibit water and nutrient transport and cause stunted root growth. Loose soil helps the earthworm circulation provides proper aeration and fertilizing effect. The wire went up to 6 inches which showed moderate compactness of the soil, indicating good aeration.

Presence of living organism in soil , like earth worm is suitable for cultivating sweet corn because these organisms helps in aeration of soil. The soil organisms break down complex organic forms into simpler forms that can be easily utilized and taken up by the plants. Therefore, the soil sample is observed for the presence of earthworm, centipede or beetles for half an hour. The results revealed the presence of earthworm indicating nutrient rich and aged nature of the soil.

Soil Structure and Tilth Test

Soluble phosphate in the soil helps in the growth of the plants. Therefore, the presence of soluble phosphate in the soil should be tested for sweet corn cultivation. The sample soil would be collected and sent to laboratory for phosphate test. The result revealed that phosphate level was low in the soil.

            Nitrate compound rich soil is good for cultivating sweet corn. As the sweet corn grows well in aged manure or compost, nitrate rich soil would be suitable. The soil sample would be collected in a container and sent to laboratory for testing nitrate content. Humus rich soil is more suitable. The results showed moderate level nitrogen and absence of ammonia in the soil.

Based on the results of the soil tests, nitrogen rich fertilizers would be applied on the soil for enhancing it’s fertility rate and thereby making it more suitable for sweet corn production.

Plant site- while analyzing site, the well-drained soil has been selected after testing the composition and structure of the soil. As it is a warm season crop, the soil would be tested for aeration and water circulation capacity. The site selected for the sweet crop cultivation is at Chestnut Road in Roseville. The site was used for cultivating another crop last year which had good yield. Therefore, the site was suitable for the horticulture project.

Before planting, the texture of the soil has been examined, as it determined the nutrient retention capacity for plant nutrition. Soil textural triangle is used to determine the texture of the soil that is under tests. The plant site contained peaty soil which is suitable for growing sweet corn. The soil tests have already proved that the soil clots can be broken by fingers.

With the help of pH meter or a pH strip soil pH has been measured. For the cultivation of sweet corn, the soil pH should be within 5.5 -7. In low pH plants can suffer from magnesium deficiency. The pH tests showed that the soil from plant site have pH 6.7 which is suitable for cultivation.

Based of the availability and position of the crop field, the decision of cultivating sweet corn has been undertaken.

After getting all the results of soil testing, the soil has been proved to be suitable for planting sweet corn.

While preparing soil, weeds, rock particles trash and any other impurities are removed from the soil by digging the soil up to 8- 10 inches through rototiller. However, 6 inches deep soil is enough for sweet corn. Finally, the soil is raked to level the surface.

Addressing the level of nitrogen and phosphorus in the soil, it has been decided that the nitrogenous fertilizers is required for successful cultivation of the crop. For stimulating the growth of plant, 10-10-10 is suitable for every 100 square feet of field. The fertilizer would be spread into the soil 3-4 inches deep and then the soil would be raked. However, the soil showed moderate nitrogen content, thus potassium nitrate, calcium nitrate, about 110Kg/ha of nitrogen or 240Kg/ha of urea would be used in a systematic manner. . Other fertilizers added for side-dressing are applied during the stages of early tasseling.  Using too much of phosphatic fertilizer containing high levels of cadmium can increase the level of cadmium in the soil, and that is taken up by the plants. In addition, natural fertilizers, cow dung and bio fertilizers were used.

Presence of Organic Plant Residue

The requirements for growing the plants were, the temperature should be above 12ºC. Warm climate with at least 80-120 days of frost free days is required for a good harvest. The germination process takes place at 18ºC. The plant requires an optimum temperature of 24ºC to 30º C. Adequate moisture in the environment is a requirement for the growing season, especially during the stages of flowering. Waterlogged conditions are avoided since it is detrimental to the growth of the plant. Calculated decisions helps minimize environmental risk associated with the use of fertilizers, herbicides, pesticides.

Watering is important for keeping seeds wilting, especially during maturation and kernels forming. After planting, regular monitoring with watering was done and supervised. Water is sprinkled over the field in adequate amount, and it helps to avoid water logging environment in the area.

Strict monitoring was carried out with tilling and plowing the soil at the plant roots. It helped soil aeration along with rapid growth of soil. Few corn plants experienced viral disease and they were removed immediately from the yard. When the plants are 2 feet tall, 1 cup of fertilizer has been applied for every 10 feet of garden row and scattered evenly within rows.

The seeds are planted at a distance of 15 centimeters. Distance is an important factor as the fertilization of sweet corn is done by pollanization and cross pollanization cannot take place without proper distance. Thus controlling distance during plantation has been monitored properly.

Water stress can cause damage to the plant and hinder their growth. Thus, water stress elimination is important during the pollination stage, as at this stage leaf rolling can occur due to water stress. Therefore, with strict monitoring soil irrigation has been done for reducing soil dryness. With the help of enviroscan, the soil moisture has been monitored during the maturation and germination phase.

The main disease observed in sweet corn seed are smut and stewart’s disease. Thus, in this cultivation project, the tolerant or cultivar resistant sweet corn seeds have been used. This disease is carried by flea beetles, thus beetle control is also needed. After purchasing the seeds, seeds were dusted with Thiram or captan.

For controlling insects in the sweet corn field carbaryl (sevin) has been used which is useful for controlling corn earworm. The insecticide has been applied approximately 4 times throughout the session. The biopesticides has also been spread in timely manner along with an integrated pest management program (IPM).

Effective weed control stops the perennial weeds that grow in any soil. A month before the actual sowing of the crop seeds, the field has been treated with herbicide and then covered up with the help of a cover crop.  Then at the time of planting, the field has been ploughed deeply to eliminate unwanted seeds and roots that may germinate and become unwanted weed in the field. Another round of herbicide has been sprayed over the area with the spray band fixed at 150mm wide. The row spacing of the herbicide is kept at 900mm. This reduces the amount of herbicide applied to the field per square feet. Finally, boom spay has been applied.

Soil Workability Test

The plan of plant establishment has been focused upon the cultivation of sweet corn. We got an order from the client to make horticulture of sweet corn in a small field in the yard. Good quality seeds had been purchased for planting. At first, the site was examined for suitability of growing sweet corn. From the previous reports, it has been analyzed that the field gave good yield in previous season. After documenting the previous reports, the soil sample has been tested for its composition, texture, pH, compatibility. The overall status of the soil was good; however, there was moderate level of nitrate level in the soil. Thus, the nitrate rich fertilizers and cow dung have been applied along with digging and watering the field before planting. After approval of the cultivation after soil tests, the temperature and climate updates were checks for suitability of cultivation. The plant beds were made by vigorous digging and enabling sunlight and water to pass through it and to reduce the chance of water logging.  

After preparing the plant bed, seeds were planted at 15 centimteter distance and water was sprinkled over the area regularly. The pH of the soil has been measured regularly and maintained within 6.5- 7.0 range.

The plants were grown in three stages. The first stage of rapid growth that happened for four weeks after the emergence of the first shoot. It existed for 25 days which was again followed by tassel growth or emergence of the tassel. The stem undergone rapid elongation. The determination of ear size was done at this time. Next stage is the pollination stage that lasted 7 days. Stress in this period causes delayed silking, and it prevents the kernel development at the tip. The final stage is all about silking. It is not as important as that of the previous stages. This last stage lasted about 12 days. The kermel fill can be reduced if stress is introduced at this stage. 

During the pollanization state environmental risk management IPM were tightly regulated for stimulating pollanization and fruit formation. The above mentioned pesticides, insecticides which were narrow spectrum, applied on the field for improving the crop yield. In addition, the natural beneficial organisms were also identified in the field. With the help of cultivation consultant, proper Integrated Pest Management (IPM) is a process of minimizing the risk to the environment and the people working in the field. It focuses on the long-term prevention of pests and the damage they cause by bringing about diseases. A well defined integrated pest management program focuses on these aspects: identification of the problem, making plans for prevention of pest infestation, monitoring the implemented plan, and controlling the associated problems and factors that aggravate the problem. IPM can be managed by both chemical and biological means. Biological pest control is more preferred than the chemical ones.

An integrated package of activities for managing pest is more sustainable than one broad-spectrum insecticide alone. The IPM for this sweet corn cultivation project includes:

Scouting (monitoring) - monitoring is a critical step in the crop protection cycle. Thus, proper training of the project team was undertaken for providing adequate care and monitoring of the plants. I addition, a crop consultant was appointed for monitoring the growth of plants and making the spray decision. Monitoring included the maturity of heliothis eggs on the leaves and stems and the number of other pests such as head caterpillar, fruit beetles and dried fruit beetles. Monitoring also included the documentation of types and numbers of beneficial insects present on plants. Here, Trichogramma pretiosum has been identified which is beneficial for controlling heliothis pest.

Biological and narrow spectrum insecticide usage- According to the data produced by ‘Insect Pest Management in Sweet corn’ in support of the registration of Success and Gemstar with Australian Pesticides and Veterinary Medicines Authority for sweet corn in Australia, Gemstar and Spanosad has been applied on the crop field. Gemstar is an insect specific virus (Nuclear Polyhedrosis Virus) which can kill heliothis. Spinosad has been used against pests which consist of secondary metabolites of Saccharopolyspora spinosa and it has low toxicity against beneficial organism. Narrow spectrum pesticide usage is also useful for reducing the resistance of pests towards pesticides.

Naturally occurring beneficial - The naturally occurring beneficial organisms help to control the major pest of sweet corn. Trichogramma pretiosum has been identified.

Pesticide application- The pest application strategy which has been undertaken was the application of the pesticides to the cob and silk area. Then the modified boom sprayers have been applied for improving yield. In this context, the most beneficial pesticide has been selected through a trial. With the help of consultant, the sprays were applied on the specific plant part.