Improving the profitability of onions grown on aging muck soil that has high pH

View the project final report

• 2010 annual report

Commodities

• Vegetables: onions

Practices

• Crop Production: foliar feeding, application rate management, tissue analysis
• Education and Training: demonstration, extension, farmer to farmer, on-farm/ranch research
• Soil Management: soil analysis, nutrient mineralization, soil chemistry, organic matter, soil quality/health
• Sustainable Communities: sustainability measures

The problem with growing onions on aging muck soils in the Northeastern United States is that the pH is above the optimum for growing onions, which results in reduced yield and profitability, and environmental contamination. If the pH issue could be addressed via altered management practices, the production of onions on aging muck soils could be sustained and phosphorous (P) loading into water ways reduced significantly. To remedy this situation, an acid forming fertilizer such as mono ammonium phosphate (MAP) or di-ammonium phosphate (DAP), and manganese sulfate can be applied in a band at planting 2-3 inches below the seed, which will reduce the pH and improve the availability of P, manganese (Mn), zinc and boron. Using this strategy, all of the P will be applied to the target area (i.e. within the reach of plant roots) where the pH will be desirable for its availability (i.e. less than 6.0). Ultimately, the amount of P that escapes as a pollutant to waterways will be reduced, because it will not be applied in the row middles where it is unavailable to the crop and free to escape into the environment. The focus of this project is to evaluate, demonstrate and encourage the adoption of this sustainable practice, as well as to evaluate whether foliar applications of Mn and P to onions deficient in Mn and P will benefit the crop. To better understand the relationship between pH, nutrient availability and yield under highly variable field conditions, we plan to monitor pH and available macro- and micro-nutrients in the soil, and compare to plant health, maturity and yield in several fields over a wide range of soil pH. Together, we will use the results generated from this project to make fine-tuned recommendations to onion growers that will help them to become more profitable and better stewards of the land.

There is opportunity for growers to improve the productivity of onions grown on aging muck soils with high pH and to reduce P loading into waterways by improving nutrient availability and uptake, especially of P and Mn. This can be achieved by applying these nutrients in an acidic fertilizer band 2-3 inches below the seed at planting and with nutrient foliar sprays. The focus of this project is to evaluate, demonstrate and encourage the adoption of these sustainable practices.

Objective 1. Reduce the pH within the row to improve nutrient availability and reduce phosphorous pollution into waterways:

Although it is cost-prohibitive and impractical to reduce pH by applying sulfur to muck soils that contain extensive amounts of marl or free limestone (i.e calcium carbonate), as is the case in many of the muck lands in New York, it is possible to reduce the pH within the plant row. This can be accomplished by using acid forming fertilizers such as mono ammonium phosphate (MAP), di-ammonium phosphate (DAP), ammonium sulfate or manganese sulfate applied in a band at planting 2-3 inches below the seed to improve the availability of P, Mn, Zn and B. The resulting pH within the row will probably be between 5.0 and 5.5, but the effect will not extend very far between the rows. In this study, nitrogen (N) and potassium (K) will be applied broadcast and incorporated prior to planting, and then the full rate of P and Mn fertilizers, which are acidic, will be applied in a band below the seed at planting. Using this strategy, all of the P will be applied to the target area (i.e. within the reach of plant roots) where the pH will be desirable for its availability (i.e. less than 6.0). Ultimately, the amount of P that escapes as a pollutant to waterways will be drastically reduced, because it will not be applied in the row middles where it is unavailable to the crop and free to escape into the environment. Over time, it very well may be realized that with more efficient use of P, rates can be reduced for banding compared to broadcast applications. Fertilizer prices of P have at least doubled within the last 4 years, a trend that is not expected to retreat, thus in addition to the obvious benefits to the environment, using lower rates of P will reduce input costs considerably in the long term.

According to Darryl Warnke, Muck Soil Scientist, Michigan State University, several years of research in Michigan has demonstrated that early onion growth and subsequent onion bulb yields can be improved with the banding of fertilizer 2 to 3 inches directly below the seed and within 2 to 3 inches to the side and slightly below the seed. Banding fertilizer 4 or more inches away for the seed had minimal benefit. In Michigan, 75-80% of muck onion growers are now banding fertilizer below the seed. In New York, muck onion growers do not band fertilizer, because it requires modification of planting equipment to band the fertilizer. Once the benefits of this practice are effectively demonstrated to them, they will certainly make the changes necessary and adopt this practice. In the longer term, when reduced rates of fertilizer inputs are demonstrated, more growers, whether they have high pH of not, may adopt the practice of banding fertilizer.

Objective 2. Evaluate foliar applications of manganese and phosphorous:

When pH is greater than 6.0, Mn, P, B and Zn can become tied up and unavailable to the plant. Since B deficiencies are rare and Zn levels tend to be high in New York, Mn and P deficiencies are most likely to occur on aging muck soils with high pH and will be the focus of this project. Both Mn and P deficiencies result in slow growth, light colored foliage, delayed maturity and bulbing, and a high proportion of thick necks, all of which contribute to reduced yield and bulb quality. It is common practice for muck onion growers to apply Mn, and to some extent, P, as foliar sprays. These types of sprays are heavily marketed by fertilizer salesmen, but without any untreated controls, growers do not really know if they are getting a crop response. A crop response to these sprays would most likely occur on muck where the pH is high and P and Mn are low. Another question is whether foliar sprays of these nutrients alone without a fertilizer band, would be sufficient to correct a nutrient deficiency. If they are, than this would be a simpler technique for growers to adopt compared to banding fertilizer, because banding requires modifications to be made to their planters. The ability to apply foliar sprays as “spot” treatments only to high pH “islands” within fields and along field edges would also be advantageous. If they do not result in a positive crop response, than growers do not need to continue investing in such sprays. In this project, we plan to evaluate foliar sprays of P and Mn in the presence and absence of banding fertilizer on high pH muck soil to demonstrate if on their own they can induce a favorable crop response.

Objective 3. Determine the effect of high pH on onion yield under field conditions:

The soil nutrient results from the Elba muck land in spring 2009 showed that lower levels of Mn tended to occur where the pH was above 6.0. However, low levels of P were not always associated with high pH. Out of the 39 sub-samples that had high to very high levels of available P, 26 or 67% of them had pH of 6.0 or higher. This may be related to individual grower practices. To better understand the relationship between pH, nutrient availability and yield under highly variable field conditions, we plan to monitor pH and available macro-, secondary and micro-nutrients in the soil, and compare to plant health, maturity and yield in several fields over a wide range of soil pH. The data that we generate from this study will allow us to fine-tune our recommendations derived from the fertilizer banding and foliar spray trials to different field situations.

This project is the first of its kind: Never before has such a comprehensive study been undertaken to improve the productivity of growing onions on aging muck soils with increased pH. Never before in New York has the practice of banding P been seriously considered. This proposed project will allow us to identify, demonstrate and promote relatively simple strategies that will improve the productivity and profitability of growing onions in the Northeastern United States, while reducing P loading into the waterways, thus sustaining large-scale commercial production of onions grown on muck soils and the quality of local water sheds for the long-term.