A wet Spring

Ajay Nair

Department of Horticulture
Iowa State University

This past week I time traveled to my nursery days and the song which I wanted to sing badly was "Rain rain go away...Come again another day, Little Johnny wants to play". Things have been fairly wet this spring. The ground is saturated and it is hard to get in the field and plant. We need the rain but it is the timing that is causing  issues. It rains and the ground starts to dry in 3-4 days but then it rains again. As compared to last year we are late in our plantings. Last Tuesday we flail mowed our cover crops (cereal rye) and gave a shallow till to dry the soil faster. We waited for three days and last Friday when we got a small window, we went full throttle and banded fertilizer and laid plastic. Banding fertilizer in the area where the plastic is laid has several advantages:

1. Less fertilizer is used

2. Fertilizer not available to weeds that grow in the alley-way between raised beds

3. Promotes sustainability by reducing fertilizer usage

Above: Cover crops being flail mowed
Below: Plastic mulch layer in action

It is unfortunate that the rain is disrupting and delaying planting, but vegetable growers should take utmost care before deciding to run any machinery in their fields. One of the concerns is soil compaction. Under wet conditions, the effect of soil compaction could go as deep as 2 feet, depending upon the axle load of the tractor.  Heavily compacted soils contain few large pores and have reduced rate of water infiltration and drainage in the compacted layers. This can can increase runoff, thus increasing soil and water losses. Compaction directly limits root growth of crops and has the potential to reduce crop growth and yield. This year it might a little tight to find the perfect soil moisture or field condition to lay plastic mulches, all we can do is be prepared and ready to get in to the field as soon as there is an appropriate rain-less window. Meanwhile, on a lighter note, I will continue with my nursery rhyme.....Rain Rain go away....come again another day......

Normal and compacted soil
(source: landscapesource.com)

Planting time musing

Ajay Nair

Department of Horticulture
Iowa State University

Weather is fascinating. It surprises you in many ways. After months of conversation about not having moisture in the ground and a slow recovery from drought, here we are, talking about too much water in the ground! The level of anxiety among fruit and vegetable producers is on the rise. We at the Horticulture Research Station are on the same page. Every time one waits for a sweet 2-3 window to till the soil and roll the plastic mulch layer, a thunderstorm rolls in with 1-2 inches of water!

Things are a little different at the eastern end of the state, thanks to the well-drained sandy soils. It rains but you can be in the field the next day. But they have their own woes with lower organic matter and water holding capacity soils. At the Muscatine Island Research Station, Fruitland, IA  our sweet corn is 2-3 inches tall and the potatoes have sprouted and getting ready to come up the soil. We installed lysimeters in our potato sweet corn biochar study on 05-08-2013 to collect water leaching out of those soils. It will be an interesting finding to know how much of nitrates are being tied up by the biochar. A large number of high tunnel growers would be happy that this intermittent rainfall is not creating problems with their planting schedules. Most high tunnel growers have planted their crop and are looking forward to a good growing year. Our tomato plastic mulch study at the Armstrong Research Station, Atlantic, IA got planted 05-10-2013.

  

    Sweet corn at Muscatine

Lysimeter installed

Plastic mulch study at Armstrong Research  Station

Our lab was all excited for today (05-20-2013) to start laying our plastic mulch but the rain last night played a spoilsport. Oh well, there are things to get done in the lab. So here we are, waiting 2-3 days for that perfect level of soil moisture where the plastic mulch is laid down to perfection (straight, tight, and with good soil contact). 

It is Transplant time !

Ajay Nair

Department of Horticulture 

Iowa State University

Transplant production plays a key role in determining a successful vegetable production system. Growing good plants requires skill, proper care, and knowledge of the fundamentals of crop production. With adequate greenhouse sanitation measures, good quality seed and growing medium, greenhouse environmental conditions such as light, temperature and relative humidity, proper irrigation and fertilization, and pest and disease monitoring and management, growers can produce high quality transplants that contribute towards higher yields and productivity.

Why grow transplants?

Benefits of using transplants are many: early start, uniform growth, healthy root system, and generally free from pest and diseases. One of the major advantages is that the grower has a better control over growing conditions so that the plants are ready when needed, eliminating problems associated with unavailability of transplants during high market demand, importing of diseases with purchased transplants, and planting delays due to inclement weather conditions. Vegetable transplants provide a head-start to target early-season market, insure a good stand of vegetable plants without the uncertainty of direct seeding or the added cost of field thinning, especially with the ongoing high cost of hybrid seeds, and earlier fruit maturity than direct seeded plants.

Greenhouse sanitation

The first and the foremost thing is to prepare the greenhouse for transplant production. Practice good sanitation. Transplant production greenhouses should be free of plant debris, accumulated soils, and weeds which may harbor insect pests and diseases. Greenhouse benches, floors, should be properly disinfested prior to use. Products such as chlorine bleach, Green-Shield, Physan 20, Oxidate (hydrogen dioxide, BioSafe Systems), chlorine dioxide, etc. could be used to clean and sterilize greenhouse benches. Product labels need to be followed precisely depending upon purpose and mode of use. Disinfecting  benches and floors is an effective method to prevent disease causing organisms such as Pythium and Rhizoctonia. Sanitation is also applicable to personnel entering and handling plants in the greenhouse. This will help eliminate spread of pest and diseases due to human contamination (dirty hands, handling plants after smoking tobacco, and soil and dirt carried in shoes).

 Ventilation and heating

Greenhouses should ensure proper ventilation, air flow, and heating for healthy plant growth. Good ventilation and air circulation is important as it helps keep the foliage dry and mitigate various bacterial and fungal diseases. Well aerated and ventilated greenhouse can maintain low relative humidity thereby eliminating common diseases such as botrytis gray mold and late blight. Growers should make sure that there heaters and furnaces are properly working and maintaining desired air temperatures. Uniform temperatures are essential for adequate control of plant development and production of uniformly sized transplants. Thermometers should be placed at plant level in several locations to monitor air temperature. Temperature control is critical and should be tailored based on crop requirement. Most plant species grow very little at temperatures less than 45 to 50 degrees F (warm season vegetables like solanaceous crops) while cool season vegetables like lettuce, spinach, cabbage, broccoli, etc will grow under temperatures not suitable for warm season vegetables.

Flats and plugs

Multi-cell plastic trays are widely in use for transplant production. These trays are available in wide range of cell sizes. Cell sizes could range anywhere from 50-800. Selection of tray size depends upon plant species, duration of transplant growth, and available greenhouse space. Larger cell sizes can be used for transplants that need longer growth cycle (>5 weeks) and have larger root system like asparagus. Larger cell sizes have the advantage of holding more media, thus moisture and nutrients, but compromise on greenhouse space. For smaller cycle crops such as leafy greens a smaller cell is appropriate as the root growth seldom fills the cell space. Most growers reuse transplant trays and containers for economic and environmental reasons. Trays and containers should be sanitized with sanitizing solutions after each use to prevent the spread of diseases. Cell sizes also have an impact on spread of diseases, as closely packed cells increase relative humidity and create conducive environment for bacterial and fungal growth.

Seed quality

Seed quality is an important parameter that is critical for successful transplant and crop production. High quality seeds have higher germination percentages as compared to old seeds that often have poor germination and reduced vigor which leads to lost uniformity, revenue and productivity. If using older seeds, perform germination tests preferably a month before the actual start date of transplant production. When purchasing new seeds, growers should purchase seeds from reputed and trusted seed firms and select cultivars that are adapted to ones area and growing conditions.

Growing media

Vegetable growers have the option of using soil mixes or artificial mixes when producing vegetable transplants. The best growing medium is the one which has good moisture-holding capacity, good drainage, and high nutrient retention capability. There is a huge selection of various soil-less commercial media available for transplant production. These soil-less mixes are sterile, easier to handle and in addition carry small quantity of start-up fertilizers for initial seedling growth. In case of soil mixes, it should be made sure that the soil is sterilized, light, well drained and free of herbicide and pesticide residues. A soil test could be useful to correct for pH and fertility problems.

Irrigation management

The success of transplant production can be stymied by improper irrigation management. Proper irrigation management is crucial to produce strong, sturdy and healthy transplants that grow well and yield a quality crop. Some things to consider while making irrigation decisions are when,

how, and how much to water. In early stages of seed germination it is critical that the media is kept moist at all times. As the seedlings grow roots and get established water the plants only when moisture is needed. Water should be evenly distributed across the flats and uniformly applied without missing corners of flats and benches. Irrigation schedule would depend on plant species, flat or container size, crop growth, and prevailing environmental conditions inside the greenhouse. Over-watering, a very common error, results in restricted root growth and poor quality plants that are susceptible to insect pest and diseases. Over watering often promotes growth of fungus gnats and certain diseases especially damping-off. It is a good practice to water the plants in the morning, to permit foliage and soil surfaces to dry before evening. Plant water uptake is influenced by cloudiness, sunlight, and temperature thus water sparingly on cloudy days.

Nutrition management

Fertigation, or the use of water-soluble fertilizers at the time of each watering, is a common method of fertilizing vegetable transplants. No generalized fertilization regimen is available but a common alternative include a 75 to 100 ppm N solution applied twice weekly, or a 300 to 500 ppm N solution applied once a week. If higher concentrations of fertilizer are used periodically, it is recommended to occasionally flush the root zone in order to mitigate salt accumulation. Adjust fertilization according to temperature and light conditions. Tall and leggy transplants are produced as a result of low light conditions coupled with high fertilizer rates, and/or over watering.

Greenhouse lighting

In the northern climate zones like the Midwest, short day lengths lack of sufficient quantity of light during spring season can adversely affect transplant production and limit plant growth. High-pressure sodium lamps (400 watt) are commonly used for supplemental lighting in greenhouses; however, escalating energy costs make their use cost-prohibitive. Research is ongoing in various US universities including Michigan State on standardizing and optimizing the use of LED (Light Emitting Diodes) lights for use under greenhouse conditions.     

Pest and diseases

Warmer temperatures inside greenhouses promote optimum transplant growth but also create environment for rapid growth and development of pest and disease populations. The best approach to keep greenhouse clean and transplants free of pest and diseases is to develop a management plan based on sanitation, monitoring, and understanding of pest and disease life cycle. A good article to read in this regard is the article on integrated pest management in greenhouses on ATTRA website (http://attra.ncat.org/attra-pub/PDF/greenhouseipm.pdf). Three insect pests that present the largest routine problems in the greenhouses are white fly, thrips, and fungus gnats. Disease organisms that cause root rots are also a grave concern as initial phases of seed germination and the early stages of seedling growth are highly susceptible. The best control for pests and diseases is proper greenhouse sanitation, proper formulation of the growing media, proper irrigation scheduling, fertilization practices, and constant monitoring and removal of infested or infected plants. A number of disease problems can be minimized by keeping the water off the foliage and low level of relative humidity in the greenhouse. Under severe outbreak of pest and diseases selective insecticides and fungicides should be used according to labeled rates and timing.

Hardening off

Plants should be acclimated to the shock and stress of transplanting into the field by hardening them off. This can be achieved by removing the optimum growing conditions of the greenhouse by reducing the amount of water and/or fertilizer and reducing greenhouse temperature by 5-10 degree F. Alternatively transplants can also be hardened by moving out of the greenhouse and placing them in a lath house for a week or two before transplanting. Hardened plants can rapidly recover from transplant shock and better withstand adverse field conditions such as low temperatures and high winds.

Tomato Grafting and Pest Management Workshop

Ajay Nair

Department of HorticultureIowa State University

Tomato Grafting and Pest Management Workshop

Ames, IA. Come learn how to graft tomatoes and manage insect pests and diseases in your tomato plantings. This workshop will provide information and show proper techniques of grafting and handling of grafted plants. The workshop will also cover insect and disease management in tomato production. There will be live plant samples to learn how to identify pests, diseases, and their symptoms. Master gardeners, general public, and commercial vegetable growers will find this workshop beneficial as it will provide hands-on grafting experience. The event is scheduled for 12 March, 2013 starting 9:30am at Reiman Gardens, Iowa State University.

SCHEDULE
9:30am	Welcome, registration and coffee
10am - 10:45	Basics of tomato grafting: Advantages and techniques – Ajay Nair, ISU
10:45 - 11:30	Hands on Grafting Exercise – Ajay Nair and Brandon Carpenter, ISU
11:30 - 12:30	Lunch
12:30 - 1:15	Managing tomato diseases – Erika Salaau-rojas, Plant Diagnostics, ISU
1:15 - 2:00	Insect pests of tomatoes and their management – Laura Jesse, Plant Diagnostics, ISU
2:15 - 2:30 pm	Discussion, Evaluation, Adjourn

This event is sponsored by ISU Extension and Outreach, the Leopold Center for Sustainable Agriculture, and the Practical Farmers of Iowa.To register please click the link below. Registration is $35 per person. Seats are limited so please register by 03/10/2013. For more information on the event please contact Dr. Ajay Nair (nairajay@iastate.edu; 515-294-7080).

http://tomatografting.eventbrite.com

It could be salty out there !

Ajay Nair

Assistant Professor, Department of Horticulture
Iowa State University

High tunnels are simple, plastic-covered, greenhouse-like structures that are passively ventilated and heated and the crops are grown directly in the soil. Over the last 4-5 years, an increasing number of fruit, vegetable, and flower growers have added high tunnels or are considering adding them to their farming operation to extend the season in the spring and fall. High tunnels have become an important tool for Iowa’s specialty crop producers to extend the growing season, increase production of quality crops, and increase profitability.

The environment without rainfall, limited space, and potential climate control in a high tunnel calls for unique set of crop management skills and serious attention towards management of soils. Both chemical and biological properties of soil, associated with continuous crop production inside high tunnels, can substantially change over short course of time. An important issue most growers are reporting is the buildup of excessive salts inside high tunnels. This is due to continuous application of synthetic fertilizers, animal manures, or manure-based compost in high tunnels. Intensive use of water soluble fertilizers of N, P, and K which are salts of respective nutrients significantly contributes to the salinity issue. Composts and manures high in salts can substantially increase soil salinity especially when they are applied in large amounts. The salt is often visible as a white crust on top of the soil (Figure 1). The issue salt buildup is compounded by the lack of precipitation inside high tunnels which prevents leaching of salts.  A build-up of salts over time leads to poor seed germination, causes salt injury including burnt leaf margins, stunted plants, reduced plant vigor, and reduces crop yield. Nutrient uptake and other metabolic processes can also be disturbed by soil salinity.

Fig. 1 Salt crust on soil aggregates inside high tunnels

One way for growers to keep track of salt levels is to regularly test their soils. Soil testing at least once a year will provide data on soil nutrient levels for proper nutrient management and help monitor soil attributes such as pH and salinity. Salt concentration in soil is estimated by testing the electrolytic conductivity (EC) of the soil. Soils with higher salt concentration have increased EC as compared to pure water which does not conduct electricity that well. There is lot of information available on ranges of soil EC that are detrimental to plant growth and cause plant injury; however, information on the method applied to measure EC is equally important to know. Depending upon method used, EC values change and so do the interpretation of those values. Three methods are generally used to measure soil EC.  The saturation paste extract method (SPE) is the most commonly used laboratory procedure for determining conductivity. In this method the soil sample is saturated with distilled water and mixed to a paste consistency. After letting the paste stand for one hour, the electrical conductivity of water extracted from the paste is measured using electrodes. A variant of this method involves measuring conductivity from a 1:1 or 1:2 soil-water mixture. In this case EC is measured after 15-20 minutes of shaking. The latter methods take less time but often are not as well related to the soil solution as is the SPE method. Electrolytic values from the 1:1 extracts are typically lower than those of SPE extracts due to increased dilution. Despite the differences in results between the two methods, many soil salinity samples are analyzed using a 1:1 extract because of reduced monetary and time investments. A conversion factor is used to convert EC values between two methods; however, value of the conversion factor is influenced by soil texture and organic matter content of the soil. A general rule of thumb to convert EC value obtained from 1:1 method to SPE method is to multiply by 2. So, an EC value of 1.5 dS/m from 1:1 method is equal to 3.0 dS/m in the SP method. Most plant responses to salinity levels reported in literature are based on values obtained from the SPE method. Table 1 shows various levels of EC at which plants show salt stress symptoms.

Table 1. Electrolytic Conductivity values from Saturated Paste Extraction method and respective plant responses

Electrolytic conductivity (dS/m)	Plant Response
0 - 2	Optimum plant growth
3 – 4	Plants show initial stress symptoms; smaller leaves
5 – 7	Growth affected; smaller and distorted leaves; reduced yields
>8	Detrimental to plant growth; plant death; only salt tolerant plants can survive

Different plant species have various levels of salt tolerance levels (Figure 2). Plants with higher drought tolerance typically handle increased soil salt concentrations better than more drought susceptible plants. Table 2 below provides information on threshold values beyond which crops would show reduction in yields.

Fig. 2 Salt stress symptoms on pepper crop

Crop	EC (dS/m)
Beans	1.0
Broccoli	2.7
Cantaloupe	2.2
Carrot	1.0
Sweet corn	1.7
Cucumber	2.5
Lettuce	1.3
Onion	1.2
Pepper (bell)	1.3
Potato	1.7
Tomato	2.5
Watermelon	2.0

High tunnel growers should periodically check their soils for salinity issues and take steps to prevent high salt build up. Under high tunnels, investment per square foot is high and any crop damage or injury would significantly reduce profitability of the production enterprise. Below are some steps growers could take to prevent salt build up in their high tunnels

1.      Flush out salts periodically. This can be done by removing the cover, leaving the tunnel open, or flooding the tunnel with water to leach out salts. Flooding could be an expensive option, but leaving the tunnel sides open during the winter months is less expensive and doable. This would allow the snow to get in (certainly in a windy area for which Iowa is a strong contender). Alternatively when changing tunnel cover every 3-4 year, it could be left open for a period of time for the natural precipitation to get in

2.      Provide adequate drainage inside the high tunnels.

3.      Use of cover crops to improve soil organic matter and soil structure, reduce compaction, and improve drainage (installation of drainage tile pipes)

4.   Judicious use of water soluble fertilizers and compost.

R.I.D.S to get RID of dirt !

Ajay Nair
Department of Horticulture
Iowa State University

To have an effective research program you need sharp, curious, and committed graduate students. I should say my lab has one. Brandon Carpenter has been working in the Sustainable Vegetable Production Lab for a year now. He is working on the biochar project assessing its implication on carrot and pepper production. In his free time Brandon has constructed a number of cool gadgets for the lab (mechanical seed transplanter, sweet potato and tomato grader, compost bin, and now RIDS (Repurposed Inexpensive Drum-washer Sanitizer). There are many aspects of vegetable production that need to be addressed by growers who are looking to keep their customers safe. Brandon and his team of students at Iowa State University’s Horticulture Research Station in Gilbert Iowa sought to answer this question by building a drum washer to clean and sanitize produce grown at the station. The foundation of the drum washer is a platform for a composting drum. The platform consisted of a frame, two axles with pneumatic tires, and an electric motor. The frame is not the only part of this project that is finding new purpose. The drum is piece of corrugated pipe that originally served as a spool for a large role of drainage tile.

There were a few minor adjustments that needed to be made to the drum after it was made, but none of the changes were major. One of the first changes made was to add baffles in the form of PVC pipes that run the length of the drum. This was done to get the produce to role and the drum turns. Before this modification was made the produce would climb the side of the drum, as it turned, then the produce would slide back down to the middle of the drum without rolling over. Some of the heavier soils were not being removed, so strips of indoor-outdoor carpet were also added to the inside of the drum. It is thought that this is due to the weakness of the spray nozzles being used. The spray nozzles, from TeeJet, are basic cone shaped nozzles that would be used on herbicide sprayers. These nozzles were chosen because they are inexpensive and readily available.

The drum washer is now operational, although it does not yet have the ability to sanitize produce. The intention for the future of this washer is to improve the spray boom to better rinse the produce, and to have one of the two spray booms attached to a chlorine injector, so produce will be sanitized as the soil is being removed. The second spray boom will then rinse the chlorine off.

Radish production in soil benches

Ajay Nair
Department of Horticulture
Iowa State University

Students from the HORT 471 class (Vegetable Production and Management) conducted experiments to assess the feasibility of growing vegetables in soil benches. They chose radish as one of their crops and learned about growing a radish from seed to completion. They made decisions on crop spacing, nutrient and irrigation management, harvest timing, and assessed the final quality of the produce. The video below illustrates the project.

In Iowa to boost local food supply during winter months, leafy and some root vegetables could be grown in soil benches provided adequate amount of heat is available. Growing crops that are adapted to cool conditions and do not require much heat, could increase the supply of locally grown produce during fall and winter months.