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| Wednesday, January 03, 2007 |
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Frequently Asked Questions – Seeding & Establishment of Pulse Crops
Seed Testing To
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Why is seed testing important? Prior to seeding, seed should be tested for germination, seedling vigour and diseases. Seed lots with poor germination will result in poor crop stands or higher seeding rates to compensate for low germination. Seedlings low in vigour take more time to emerge; are more prone to infection by soil-borne diseases; have poor utilization of nutrients and water; are more susceptible to inclement weather; and can’t provide sufficient canopy cover to compete with weeds. Each of these factors contributes to poor crop stand and low yields. Seed lots with high disease ratings (especially Ascochyta, Anthracnose and Botrytis) should be avoided. Planting seed that is free of diseases helps limit the introduction of pathogens in the field and prevent early establishment of disease. What is the safe disease rating on seed for planting? There are no official “safe” infection levels for planting. The more disease-free the seed, the better it is for seeding. The decision to use infected seed lies entirely with the farmer – after considering such factors as: cost and availability of disease-free seed; cost and availability of registered seed treatments; weather conditions and disease pressure; type of pulse crop; type of disease; and cost and availability of foliar fungicides. Below are unofficial guidelines that may be used when planting seed with seed-borne pathogens.
What is the right time to seed pulse crops? Lentil, pea and desi chickpea can be seeded early (late April to early May) as long as the top 2.5 cm (1 in.) of the soil has reached 5 oC. They can tolerate light frost (-4 to -6 oC). Kabuli Chickpea should be seeded mid May when soil temperatures of 10 oC have been attained in the top 5 cm (2 in.) of the soil. Dry beans should be seeded in late May when frost risk is low and soil temperature at seeding depth has reached a minimum of 12 oC. These guidelines are not a guarantee that early seeded crops will survive any late spring frost. Frost survival depends on how low the temperature gets, how long the freezing conditions last, how much cold conditioning the crop received, moisture content and the growth stage of the crop when frost hits. Table 2 shows survival rates of beans and field pea at four different stages and freezing temperatures. The survival of the crop after a frost also depends on the crop’s ability to regenerate itself. For instance, even if the frost is severe enough to kill the main shoot, a lentil, pea or chickpea plant can regrow from one of the scale nodes at or below the soil surface. Beans do not have such scale nodes.
What seeding rate should I use? The seeding rate should be aimed at achieving the optimum plant population density. The recommended number of plants/ft2 is as follows: lentils – 12; field pea – 8; dry beans – 3 for irrigated and 4 for dryland; and chickpea – 4. Other factors to be considered are seed size as given by thousand kernel weight (TKW) in grams, as well as percentage survival based on germination and seedling vigour tests. If only percentage germination is known, it can be used, but it would be advisable to adjust it lower, considering that some germinated seeds may not emerge due to low vigour. Thus, the simple calculation is performed as shown below: Seeding rate (lb./ac.) = [(Plants/ft.2 x TKW g x 10) ÷ (% Survival)] Seeding rate (bu./ac.) = [(Seeding rate (lb./ac.)) ÷ (lb./bu. of the grain)] On average, the test weight for pulse crops is 60 lb./bu. For more information check out Frequently Asked Questions - Pulse Crop Seeding Rates and Rolling.
No. Inoculants contain rhizobia, which are only compatible with specific pulse crops. Ensure that the inoculant that you purchase is recommended for the crop you are planting. The rhizobium species Rhizobium leguminosorum is compatible with field pea, lentil and fababean. Chickpea and dry beans are compatible with R. ciceri and R. phaseioli, respectively. However, even when the same species can cause nodulation of more than one type of pulse crop, specific strains of the rhizobium have different nodulation effectiveness. For that reason, inoculants are formulated using the best strain for specific crops. Hence, single strain inoculants contain only one strain considered the best for a specific crop. Other formulations, referred to as mixed, contain a strain intended for use on more than one crop. In this case, the manufacturer incorporates the best strains for the intended crops. Do I have to treat my pulse seed with a fungicide? Fungicide seed treatments are used to protect seed and seedlings against certain seed-borne and soil-borne diseases, and act as an assurance for vigorous seedling establishment and a good plant stand (refer to labels for details and directions.) As early seeding is recommended for most pulse crops, the seed is planted in cold soil and emergence may be prolonged, thus increasing the risk of disease infection. If disease pressure is low and conditions aren’t conducive for the pathogens, the advantages of seed treatment may be low. However, it is not known exactly when that is. Won’t the fungicide kill the rhizobium inoculant? Rhizobia are sensitive to some seed-applied fungicides. When using a combination of fungicide and inoculant, consult inoculant product labels and company compatibility fact sheets for the various methods fungicides can be applied to pulse crops. One method is to apply the fungicide to the seed first, allow it to dry and apply the inoculant immediately prior to seeding (sequential method). Once inoculated, plant as soon as possible as delays can reduce the efficacy of the inoculant. Prolonged exposure of the rhizobium may lead to desiccation and/or toxic effects. Granular inoculants are separated from the seed, thus providing protection to the inoculant. Studies (Matus et al. 2004) show that, when applied as recommended, seed treatments have no significant effect on rhizobium and the capacity to fix nitrogen.
Do I have to apply fertilizer? Pulse crops have a high demand for plant nutrients. Although pulses fix nitrogen, this does not happen immediately. Soils extremely low in N may benefit from a small amount of starter nitrogen. Often, all the starter nitrogen that is required can be provided by applying a safe rate of monoammonium phosphate (e.g. 12-51-0) with or near the seed. For field pea, lentil and chickpea, if soil nitrogen level is very low in the top foot of the soil (less than 15 lb./ac.) at planting, a small amount (up to 18 lb./ac.) of starter N fertilizer may benefit the crop when banded away from the seed. As a rule of thumb, if soil test indicates more than 20 lb./ac. of nitrate N in the top foot of the soil, sufficient nitrogen is available and adding more would only result in suppressed N fixation and delayed maturity. Field pea, lentil and chickpea have a relatively high requirement for phosphorus (P). Phosphorus is needed to promote the development of extensive root systems and vigorous seedlings with vigorous root growth necessary to promote good nodule development – important for the nitrogen-fixing process. The maximum safe rate of actual phosphate applied with the seed is 20 lb./ac. for lentil and 15 lb./ac. for chickpea and field pea under good to excellent moisture conditions. If higher phosphate rates are required, banding the fertilizer away from the seed should be considered. If sidebanding is available, a rate higher than safe rate of phosphorus can be sidebanded, especially when using narrow openers with wide row spacing. Field pea has a high demand for potassium - about 140 lb./ac. for a 50 bu./ac. crop. Fields low in potassium should be corrected based on soil test recommendations. Banding potassium fertilizer is effective. Soils testing low in available sulphur should have this deficiency corrected by using ammonium sulphate. For instance, a 30 bu/ac lentil or a 40 bu/ac pea crop requires about 10 lb./ac. of sulphur. Ammonium sulphate can be broadcast or banded away from the seed. Nitrogen fixation has been found to be poor with beans. The new granular inoculants may improve the crop’s capabilities. Currently, it is recommended that you apply 50 lb./ac. starter N as a sideband. Phosphate fertilizer is best sidebanded with the N for bean production to avoid any injury to the seed because of high cost seed and low recommended plant densities for bean in narrow-row dryland production.
Do I have to apply phosphorus if I use JumpStart®? If soil tests indicate low to medium levels of available phosphorus, you may need to apply phosphorus fertilizer. JumpStart® is neither a fertilizer nor a fertilizer substitute. It is composed of a soil fungus Penicillium bilaii that makes less available forms of phosphates more available to the plant. Refer to company fact sheet for details. What if my granular inoculant doesn’t flow properly? Granular inoculants absorb moisture and form clumps that plug the distributor slots of the hopper. With early discovery of this problem you can return to the poorly inoculated area and sideband the inoculum. However, if germination has started, this remedy may result in seedling damage and poor stand. The solution is to apply a top dressing of N fertilizer. Crop monitoring for N deficiency symptoms and plant analysis and soil testing may help to confirm need for top dressing. However, be warned that by the time symptoms show, it may be too late to correct the N deficiency. When using granular inoculants, do not leave the inoculant in the hopper for prolonged periods of time. Which herbicide residues should I worry about for my pulse crop? Always keep a record of herbicide use for all your fields. Refer to the SAF Guide to Crop Protection for information on recropping restrictions. Also check product label for details. Can I use seed from previous year glyphosate-desiccated crop? No. Glyphosate residue within seed results in increased field mortality of both germinating seed and seedlings. Seedlings that do survive lack vigour due to the development of abnormal root systems. Roots tend to be gnarled and twisted with little branching as well as devoid of root hair development resulting in poor nodulation. A land roller can be used in lentil, field pea and chickpea fields to provide a smooth and level surface for harvest. Land rolling can be done in lentil and field pea before or after the crop emerges. Post emergent land rolling can be done up to the 5 – 7 node stage in lentils and 5 node stage in peas. Land rolling beyond these stages can damage plants, increase the spread of foliar diseases and reduce yields. Rolling should not be done on wet soils or when the crop is damp or stressed by extreme heat, frost or herbicide application. Land rollers are less beneficial in chickpea production than in pea and lentil production since chickpea does not usually lodge and the stubble height is greater. Rolling should only be done before crop emergence. Post-emergent land rolling is not recommended as it may spread disease such as ascochyta blight and can cause mechanical injury because chickpea seedlings develop stiff stems early in their development. Beans should be rolled within three days after seeding but rolling after seedling emergence is not recommended. For more information check out Frequently Asked Questions - Pulse Crop Seeding Rates and Rolling.
Hnatowich, G. 2005. Glyphosate Residue In Seed - Effects on nodulation. PAN All Pulse Bulletin #9 - APRIL 14, 2005 Matus et al. 2004. Effect of Jazz on the ability of rhizobium to fix dinitrogen from the atmosphere in chickpea, lentil and pea. A comparison with Crown, Allegiance FL and Vitaflo 280. http://www.ontariobeans.on.ca/MatusetalproceedFinal.pdf. Meyer, D.W. and Badaruddin, M. 2001. Frost tolerance of ten seedling legume species at four growth stages. Crop Sci. 41:1838-1842. Pearse, P. and McVicar, R. 2005. Seed Quality in Pulse Crops – 2005. Philom Bios. Products. http://www.philombios.com Saskatchewan Agriculture and Food. (2005). Guide to Crop Protection Saskatchewan 2005. Saskatchewan Agriculture and Food. Various fact sheets on pulse crop production and on fertilizer applications which could be obtained from SAF web site Saskatchewan Pulse Growers. Pulse Production Manual. Prepared by S. Patrick Mooleki, Saskatchewan Agriculture and Food. For
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