Chickpea in Rotation

Guy Lafond¹, Stu Brandt², Lone Buckwaldt³, Yantai Gan⁴, Adrian Johnston⁵, Ray McVicar⁶ , Fran Walley⁷, Tom Warkentin⁸ and Albert Vandenberg⁸

¹ Indian Head Research Farm, Box 760, Indian Head, SK, S0G 2K0

² Scott Research Farm, P.O. Box 10, Scott, SK, S0K 4A0

³ Saskatoon Research Centre, 107 Science Cres, Saskatoon, SK, S7N 0X2

⁴ Swift Current Research Centre, P.O. Box 1030, Swift Current, SK, S9H 3X2

⁵ Potash and Phosphate Institute of Canada, Suite 704 - CN Tower, Midtown Plaza, Saskatoon, SK, S7K 1J5

⁶ Saskatchewan Agriculture and Food, Walter Scott Bldg, 3085 Albert Street, Regina, SK, S4S 0B1

⁷ College of Agriculture, Department of Soil Science, 51 Campus Drive, University of Saskatchewan, Saskatoon, SK, S7N 5A8

⁸ College of Agriculture, Crop Development Center, 51 Campus Drive, University of Saskatchewan, Saskatoon, SK, S7N 5A8

1.0 Introduction

Relative to other pulse crops like pea and lentil in Saskatchewan, chickpea is a relatively new crop. In 1999, Statistics Canada reported 350,000 seeded acres in Saskatchewan. However, harvested acres may be as low as 300,000 due to delayed maturity as a result of cooler and wetter growing conditions.

The objective of this paper is to bring together the latest agronomic information about chickpea production focusing on aspects pertaining to weed and disease management, crop establishment, soil fertility and inoculant requirements, and other topics such as water use, re-cropping constraints and rotational considerations. Some discussions about the difficulties experienced during 1999 will also be included. For more information about chickpea production, refer to the following Saskatchewan Agriculture and Food website address: http://www.agr.gov.sk.ca/crops/special/variety_options/chickpea.asp

2.0 Crop Establishment

A field study was conducted at the Swift Current Research Centre in 1998 and 1999 to determine the best agronomic management practices for establishing chickpeas in the semiarid prairie. Kabuli-type chickpea (var. Sanford and B-90), and desi-type chickpea (var Myles), were used in the study. The objectives of the study were to: 1. Determine the response of chickpea to phosphorous fertilizer (at the rate of 0, 17, and 34 lb P₂O₅ /ac) on crop establishment, plant growth and seed yield. 2. Determine the impacts of seeding depth and seeding date on establishment and seed yield and 3. Determine the effects of seeding the small seeded fraction of kabuli (large seed ) on final seed yield and quality.

2.1 Effects of fertilizer-P

The responses of chickpea to fertilizer-P application were inconsistent between the two years. In 1998, the chickpea seed yield increased 7 to 11%, on average, by using fertilizer-P at the rate of 17 to 34 lb P ac^-1, as compared to the non-P treatment. In 1999, however, no yield differences were found between the fertilizer-P treatments, although the fertilizer-P slightly increased dry matter production before flowering. Overall, chickpea seed yield in 1998 was 950 kg/ha, about half of the 1999 seed yield of 1990 kg/ha. Greater soil moisture in 1999 favored rhizobial activity and symbiotical N-fixation and plant growth which might have masked the possible effect from fertilizer-P as shown in 1998. A strong correlation was found between seed yield per plant and fertilizer-P rate in 1998 where the highest fertilizer-P rate (34 lb/ac) resulted in the greatest seed yield per plant. However, in 1999, this correlation did not show up. It is speculated that the better soil moisture condition in 1999 provide plants with less competition for growth resources, particularly for available water. The experiments will be repeated in 2000 to try and shed more light on this topic.

2.1 Effect of seeding depth and date

Chickpeas were planted at two depths (2 vs 4 inches). The results showed that seeding depth had a small, but statistically significant impact on seedling emergence, plant growth, seed yield and kernel weight. In both years, plants emerging from the 2" depth produced a higher (5 to 10%) amount of dry matter at flowering than plants that emerged from the 4" depth. Consequently, plants grown from the shallow depth ( 2 inches) produced 2 to 6% higher seed yield than plants grown from the 4 inch depth. The differences in dry matter production before flowering between seeding depths were more evident in 1998 than in 1999. In 1999, the early season temperatures were lower than normal, and the cool conditions slowed plant growth and thus differences between seeding depths were smaller than those observed in 1998. It was interesting to note that the mean seed weight was higher for seeds harvested from the shallow-seeded plants than those of deep-seeded plants. It appeared that the early emergence associated with the shallow seeding provides plants with advantages later in the life cycle.

Two seeding dates were used in each year with the early seeding date ranging from April 30 to May 5 and the late seeding date between May 16 to May 20. The results showed that seeding date had a significant effect on dry matter production at flowering in both 1998 and 1999 (Table 1). Averaged for the two years, the B-90 variety seeded early produced 10.8% more dry matter at flowering than at the late seeding. Similar results were obtained for Sanford; the early-seeded produced 16% more dry matter than the late-seeded.

Table 1. Effect of seeding date on the dry matter production (kg/ha) in chickpeas grown at Swift Current.

The greater dry matter production associated with early seeding translated into a higher seed yield (Table 2). By seeding chickpea early, seed yield increased 10 to 16% for B-90 and 4 to 12% for Sanford. We observed that early-seeded plants had a longer period between flowering and maturity than late-seeded plants. It is speculated that increased seed yield with the early seeding was partially due to the longer reproduction period during which more seeds were set, and more photosynthetic materials were mobilized from the vegetative organs to the seeds. In addition, early seeding resulted in earlier harvest, thereby reducing the risk of late-fall frost and lower seed quality. Kabuli chickpea grown at Swift Current had an average maturity of 95 days in 1998 and 115 days in 1999.

Table 2. Effect of seeding date on the seed yield of kabuli chickpea (kg/ha) grown at Swift Current.

2.3 Seed Size

Seed cost is high for chickpea, and pulse growers have asked if small seeds could be planted and would produce an equivalent yield as large seed. Large vs small seeds were screened from the same seed lot of kabuli chickpea var Sanford and planted in replicated trials at Swift Current in 1998 and 1999 (Table 3). We found that in both years, seed size did not have any impact on plant growth and development, nor on seed yield in chickpea. We also determine that seed size fractions were not related to the size of the planted seeds.

Table 3. Effect of fertilizer-P on Kabuli chickpea plant counts, seed yield and dry matter production at Swift Current.

3.0 Adaptation of Chickpea

Chickpea is a late maturing crop, especially when exposed to late summer precipitation. However, a dry fall can result in a high yielding crop of chickpea as was observed at Canora in 1998. In contrast, a heavy late-season rainfall at Redvers prevented the chickpea from maturing, resulting in the crop not being harvested in 1998. One would not expect to produce a good chickpea crop at Melfort, however, when mid-summer rains were followed by hot and dry conditions in August and September, it has been possible to produce chickpea in a subhumid location. Under severe drought conditions at Scott, seed size can be significantly reduced. The deep rooting habit and tolerance to water stress make chickpea a winner under these adverse late season drought conditions. There is potential risks of growing chickpea in areas that have a medium to high probability of late season precipitation, or low probability of a terminal drought.

Limited data at Scott suggests that as moisture increases, maturity of Desi chickpea is delayed (Table 4). Where available spring soil water plus rainfall from May 1 to August 31 exceeded 400 mm, the risk of frost damage prior to crop maturity was very high. During 1999, the crop was damaged by frost on both stubble and fallow, although damage was much less severe for the stubble crop. The situation in 1999 for Kabuli chickpea was much more serious, with only pods generated from the first flower to open producing any harvestable yield on fallow, while only the latest developing pods were affected on stubble. Kabuli chickpea yielded only 160 lb/ac on fallow, but increased to 1080 lb/ac on stubble in 1999 at Scott.

Table 4. Influence of stored soil water and growing season rainfall on growing degree day to maturity requirements and yield of Desi (cv. Myles) chickpea at Scott.

*Crop was frost damaged before maturing at the indicated number of growing degree days.

Based on these observations, chickpea appears best adapted to the Brown soil zone where moisture stress and terminal drought occur more consistently. Growers can reduce the risk of frost damage by growing the crop on stubble rather than fallow, and on lighter textured soils where water holding capacity is lower. This is particularly important in higher moisture areas of the parkland or where the frost free period is relatively short.

4.0 Weed Control

Chickpea is a poor competitor with weeds. However, post-emergent harrowing is not recommended as it can spread disease and cause crop injury. Early seeding, combined with optimum plant density allow the crop the opportunity to compete with weeds.

SENCOR^tm herbicide is registered for control of some broadleaf weeds in chickpea. Application should take place at the 1-3 above ground node stage (maximum crop height 6 cm). Application past this crop stage can cause significant crop injury. Consult the label for more details.

SELECT^tm is registered for the control of grassy weeds and volunteer cereals in chickpea. Application should take place in the 2-6 leaf stage of the weeds.

POAST ULTRA^tmis registered in chickpea for control of grassy weeds, volunteer cereals and quackgrass suppression. Application should take place in the 1-6 leaf stage of the grassy weeds and 1-5 leaf stage of the quackgrass.

It is very important to control perennial weeds such as Canada thistle, sow thistle or quackgrass in the years previous to chickpea. Volunteer canola, mustard, or flax are difficult to control and rotations, which include these crops prior to chickpea should be avoided.

The use of a pre-seeding burnoff with a non-selective herbicide such as ROUNDUP can be used to control winter annual and early emerging spring annual weeds. Chickpea is sensitive to herbicide drift. Producers should thoroughly clean their sprayer tank before applying any crop protection product on chickpea.

5.0 Fertilizer and Inoculant Management

5.1 Inoculant Management

As a pulse crop, chickpeas are capable of meeting some of their nitrogen requirements through the process of nitrogen fixation. Current research conducted in Saskatchewan indicates that chickpea is likely to obtain between 50% to 70% of its nitrogen through nitrogen fixation. Moreover, desi-type chickpea appear to derive a greater proportion of nitrogen through nitrogen fixation as compared to kabuli-type chickpea. Irrespective of type, however, any management strategies that increase the success of inoculation will ultimately promote better yields.

The first step in maximizing nitrogen fixation is making sure that you have the right inoculant. Using an inoculant with chickpea is essential. Our soils do not contain any native rhizobia that are specific to the chickpea. Therefore, if you are seeding into first time land, nodules will only form if you have applied an inoculant. Although their name may be misleading, chickpea is not a "pea" and pea or lentil inoculant can not be used to inoculate chickpea. In fact, chickpea has a very specific relationship with a its rhizobia (Rhizobium cicer) and you will need to make sure that the inoculant that you are using is specific for chickpea. Interestingly, chickpea inoculants that originate from south of the border will often be labeled "Garbanzo Beans" but don't worry - chickpea and garbanzo beans are one and the same and inoculant labeled "chickpea" or "garbonzo bean" is the correct choice for chickpea.

Many producers are concerned about the form of inoculant that is best for chickpea. Currently, chickpea inoculant is available as a peat-based powder and granular. There are no commercially available liquid inoculants for chickpea. Different inoculant formulations have been compared in field trials conducted in Saskatchewan over the past three years by researchers at the University of Saskatchewan (Kyei-Boahen, S., F.L. Walley, and A.E. Slinkard. 1998. Placement of granluar inoculant for chickpea. Proceedings of the Pulse Crop Research Workshop, Saskatoon, SK, Volume 3:23-24.) In these trials, two different Rhizobium strains were formulated as either liquid, peat-based powder or granular inoculants. Results from these studies indicate that nodulation (as measured by assessing nodule weight) was generally higher for the granular and peat-based powder formulations as compared to the liquid formulations. Moreover, inoculant formulation significantly affected the distribution of nodules on the root system. The peat and liquid inoculants produced more nodules on the crown region (i.e., in the immediate vicinity of the seed), whereas the granular inoculants produced more nodules on the lateral roots, particularly when the inoculant was banded to the side and below the seed.

In general, the results of this study suggest that the granular inoculants were as good, or better, than the peat-based powder or liquid inoculants for enhancing chickpea seed yield. It is important to note that these experiments were conducted on "first- time" chickpea fields and thus some of the dramatic yield responses observed in this study due to granular inoculant may, in part, reflect the fact that there were no other rhizobia in the soil capable of nodulating chickpea.

5.2 Fertilizer Management

A collaborative field research study between the Department of Soil Science and the Saskatchewan Wheat Pool (Mr. Garry Hnatowich, Research and Development) was initiated in the spring of 1996 to investigate the N and P fertility requirements of chickpea and examine the consequences of including chickpea in a crop rotation. The N and P fertility experiments with desi- and kabuli-type chickpea were conducted during a three-year period in the Brown and Dark Brown Soil zones on soils with relatively low levels of available N and/or P. In the first year of the study, four experiments (two with desi-type chickpea and two with kabuli-type chickpea) were conducted. Each experiment consisted of 12 treatments which included four levels of "starter N (46-0-0 at 0, 15, 30, and 45 kg/ha N, i.e., 0, 13, 27, and 40 lb/ac) and 3 levels of seed-placed P2O5 (11-54-0 at 0, 20, and 40 kg/ha P2O5, i.e., 0, 18 and 36 lb/ac).

Because results of the 1996 field season indicated few if any yield responses to seed-placed N and P, the field design was modified in 1997 to accommodate sideband applications of the P2O5 fertilizer. In order to accommodate the new sideband treatments in 1997 and 1998, the experiments were conducted at two, rather than four field locations. At each of the locations, experiments with both desi-type and kabuli-type chickpea were conducted.

Regular monitoring of the plots indicated that although growth stages during active plant growth (i.e., days to flowering, pod formation, etc.) were largely unaffected by N fertilizer application, seed maturity was, in some instances, extended as a consequence of fertilizer application.

Symbiotic N fixation was estimated using the difference method with flax (var. McGregor) as the non-fixing reference crop. Data suggested that increasing increments of fertilizer N resulted in concomitant reductions in nitrogen fixation by kabuli- and desi-type chickpea (Table 5).

Table 5. The impact of starter N and P2O5 fertilizer on symbiotic N fixation by desi- and kabuli-type chickpea in 1998.

Application of starter N and, in some instances, P₂O₅ enhanced midseason vegetative (i.e., biomass) yields of desi- and kabuli-type chickpea. For example, application of starter N resulted in incremental increases in midseason biomass yield of desi-type chickpea at Outlook and kabuli-type chickpea at Watrous in 1998. In some instances, application of P₂O₅ enhanced midseason biomass yields, although yield enhancements were not always statistically significant. Data suggest that placement of P₂O₅ away from the seed may have been the most favorable in terms of midseason biomass production.

Although starter N typically enhanced midseason biomass yields, the early yield enhancement often did not translate to enhanced final seed yields. Statistically significant seed yield enhancement associated with starter N application was observed only at two of the 14 individual experiments that were harvested for final seed yield and at both of these sites, stressful environmental conditions compromised the N-fixing ability of the chickpea crop (Table 6). For example, in 1998, field conditions were very dry at both of our research sites. A significant response to starter N was achieved at Outlook, and data suggest that desi type chickpea may have benefitted from the application of starter N at Watrous, although these results were not statistically significant. It is interesting to note that there is evidence to suggest that desi chickpea may not be as an effective N fixer N as is kabuli chickpea and thus tends to be more responsive to starter N. In 1998, both Outlook and Watrous were very dry at seeding and we were concerned about the ability of the crops to nodulate, given the dry seed bed conditions. We concluded that although the application of starter N typically does not enhance seed yields of well-nodulated and actively fixing chickpea, if nodulation and subsequent N fixation is compromised due to environmental stress or poor inoculation, starter N may be beneficial. However, this puts the onus on the producer to ensure that the inoculation process, and subsequent nodulation, is maximized. In addition, although the application of 15 kg/ha of N (i.e., 13 lb/ac) enhanced seed yields as compared to the control treatment, there was no additional benefit of applying increasing increments of fertilizer N.

Table 6. The impact of starter N and P₂O ₅fertilizer on seed yield of desi- and kabuli-type chickpea in 1998.

Application of P₂O₅ also did not confer a consistent seed yield advantage at all sites and over all years of the study. Moreover, it was not clear whether P₂O₅ placement influenced seed yield consistently. Although the influence of P₂O₅ on seed yield of chickpea was not consistent, it is important to note that significant chickpea seed yield increases were achieved at some sites. For example, a statistically significant effect of P₂O₅ on seed yield of chickpea was detected at Watrous in 1998 where it was observed that P₂O₅ fertilizer application generally enhanced the seed yield of desi-type chickpea (Table 6). Highest yields were achieved when P₂O₅ was sidebanded at a rate of 40 kg/ha (36 lb/ac), although this treatment was not significantly different than either the 20 or 40 kg/ha P₂O₅ rate (18 or 36 lb/ac), applied in the seedrow. A similar response was not observed for kabuli-type chickpea. In light of the important role that P plays in root development, stress tolerance and maturity enhancement, it is cautioned that significant economic losses may occur if producers do not apply P fertilizer according to soil test recommendations.

6.0 Disease Management and Control

Ascochyta L. blight is the only foliar disease of chickpea in western Canada that has the potential of causing yield loss. Fortunately, partially resistant cultivars, fungicide application, healthy seed, and proper crop rotations can reduce the risk of severe epidemics. Soil and seed borne pathogens may cause seedling and root rot, especially in kabuli-type cultivars, which have larger seed and thinner seed coat compared to the smaller-seeded desi-types. Therefore, it is recommended that kabuli chickpea seed be treated with Apron^tm at 16-110 ml per 100 kg seed. If the seed is also inoculated with rhizobium it should be planted immediately since the seed treatment will reduce the effectiveness of the inoculant. However, placement of a granular rhizobium away from the seed eliminates the direct contact with seed applied fungicied by-passing this problem altogether.

6.1 Survival and spread of ascochyta blight

Seed infected with ascochyta and crop infected residues initiate this disease. When infected seeds are planted into moist soil, ascochyta spores are formed and germinate to infect the emerging seedling. It is sometimes possible to recognize a severely infected plant in the center of a patch of plants with ascochyta symptoms. If patches of infected plants are evenly distributed throughout the crop, it indicates that ascochyta-infected seed was the source of inoculum. Infected chickpea residues from previous crops is another important source of inoculum. The fungus survives as long as the residue is present. In spring and early summer, fruiting bodies are produced on debris near or on the soil surface. These fruiting bodies contain myriads of spores, which are discharged into the air when the weather alternates between wet and dry. Spores are spread by wind within the crop or over several miles, and can therefore infect chickpea crops planted at a distance.

Some chickpea cultivars, such as Sanford, Dwelley, Myles (desi) and B-90 are partially resistant to ascochyta blight. This means that they do not become severely infected in the vegetative growth stage. However, at early flowering small red-brown spots on leaves and stems develop, which are caused by ascochyta blight. Usually infection of partially resistant cultivars starts between the flowering and pod-setting stages during periods of wet weather. Brown lesions of varying sizes develop on the bottom and middle leaves. The lesions are often surrounded by a darker margin and sometimes by a yellow (chlorotic) area. The largest lesions are 1/4-1/2 inch across. When leaves and shoots are particularly hard hit they wilt and give the crop a pale look, which explains the term ascochyta blight. On stems, lesions are darker brown and elongated often constricting the surface, thereby weakening the stem so it easily breaks. On pods, lesions are circular often with tiny, black fruiting bodies arranged in rings. The fungus is able to grow from the pod surface into the seed, which become shriveled and dark. Fruiting bodies can also be seen in many of the older and larger lesions on stem and leaves. They contain a profuse amount of spores that are exuded in a gelatinous mass. These spores are spread to other plants by a combination of rain splash and wind to spread the disease and start new infections within the crop. Spores produced on the plants are different from the air borne spores produced on chickpea residues on the soil surface. Temperatures of 20-25^oC and 85-98% relative humidity are most conducive for infection, and symptoms are noticeable four days after spores have landed on a leaf or stem. New spores are formed in only five to six days, so this rapid life cycle can result in many spore generations in a growing season, and the whole crop may be lost to ascochyta blight.

6.2 Management of ascochyta blight

The fungus that causes ascochyta blight in chickpea does not attack field pea or lentil and vise versa. A rotation with 3 or 4 non-host crops such as cereals, canola, flax or any of the pulse crops will bring about a reduction of chickpea residue and ascochyta inoculum. Where possible, a new chickpea crop should be planted at least 3 miles from previous chickpea crops and preferably up-wind of the most prevailing wind, which means west of the previous crop to reduce the risk from air borne ascochyta spores from residues. However, this will become less practical as the chickpea acreage increases across Saskatchewan.

Under most conditions, deep ploughing will hasten decomposition of chickpea straw and remove it as a source of inoculum. The ascochyta pathogen is a poor competitor to fungi that are specialized in growing on and decomposing dead plant tissue, so ascochyta is unable to colonize the debris much beyond the original lesions. Studies in the Palouse region of Washington State showed that the pathogen survived in infected plant material for more than 2 years when situated on the soil surface, but lost its viability rapidly at soil depths of 5-16 inches. We recognize that in a no-till system this is not possible so the best alternative is to ensure 3-4 years between crops. Even with conventional tillage, burying the residues at a 5 - 16 inch layer is not practical, and if practiced could lead to serious wind and water erosion.

6.3 Planting disease free seed of a partially resistant cultivar

Since infected seed gives rise to infected plants early in the growing season, it is advisable to plant seed with no or very low levels of ascochyta infection. There is no threshold for seed borne infection, since environmental conditions will determine whether infected seedlings will have a great or a small impact on the overall ascochyta severity. Presently, there are no seed treatments registered for control of seed borne ascochyta. However, as mentioned earlier, kabuli-type seeds should still be treated with Apron for control of seedling and root rot.

Chickpea cultivars such as Arizona and UC27 are highly susceptible to ascochyta and should not be planted. Several cultivars are partially resistant to ascochyta blight, such as Sanford, Dwelley (large seeded kabuli), B90 (smaller seeded kabuli) and Myles (desi type). These cultivars have a good level of ascochyta resistance up to flowering, when one or two fungicide applications might be necessary. B-90 is distributed by Terramax while the other cultivars were developed by the USDA and are publically available in Canada. Plant breeders at the Crop Development Centre have used the USDA lines in their breeding program and several new cultivars such as CDC Yuma, CDC Chico, CDC Xena and CDC Desire will become available in 2000-2001 with similar ascochyta resistance, but with improved maturity and yield.

6.4 Control of ascochyta by fungicide application

Growers should take special care to protect green and healthy foliage and developing pods, especially if blight symptoms appear, and seem to be increasing in severity over a few days. Any form of moisture at this time will favor ascochyta development. It will take a few days of crop scouting, but will be worth while.

Evaluations of the contact fungicide Bravo 500 were conducted in Saskatchewan in 1998, when weather conditions were less favorable for ascochyta, and in 1999, when frequent rainfall promoted rapid rate of ascochyta blight development. As shown in Table 7, there was only 1-3% ascochyta on July 8 and 22 when Bravo was applied in 1998. Ascochyta developed slowly that year, and there was 19% ascochyta in the untreated plots in Elrose at the end of the season. A significant yield increase to 1486 lb/ac was seen in Elrose in plots treated with Bravo two times. It should be noted that the first fungicide application on July 8 at early flower did not improve yield. The high yield and significant yield increase was attributed to the second application made on July 22 at mid flower. There was no economic return for applying Bravo in Sovereign where there was only 9% ascochyta blight at the end of the season.

The disease situation was quite different in 1999. As shown in Table 8, there was only 1-4% ascochyta on July 6 at the data of the first Bravo application, but disease developed rapidly to 72% on July 29 and to 93% on August 19 in untreated plots in Harris, and to 12 % and later 86% in Zealandia i.e., ascochyta development was slower in Zealandia, but the disease was equally severe at the end of the season. The yield was low in untreated as well as fungicide treated plots because of cool humid weather which delayed maturity. Most Bravo treatments clearly reduced the level of ascochyta. Yield was increased at both locations to between 717 and 797 lb/ac with two applications of Bravo 500, which was significantly higher than 40-218 lb/ac in the untreated plots. In years where ascochyta develops rapidly because of humid weather conditions, as in 1999, two applications of Bravo 500 starting at early or mid flowering will be economically beneficial. Foliar fungicide applications may not prove cost effective when disease pressure is low.

Table 7. Comparison of one and two Bravo 500 applications for control of ascochyta blight in chickpea at two locations in 1998.

* indicates that the treatment is significantly different from other treatments in the same column.

Table 8. Comparison of two rates, two dates and a single versus a double application of Bravo 500 for control of ascochyta blight in chickpea at two locations in 1999.

* indicates that the treatment is significantly different from other treatments in the same column.

7.0 Crop Adaptation and Rotation

A field study was conducted on a loam soil at Swift Current and on a clay soil at Stewart Valley during 1996 -1998 to determine yield potential and water use characteristics of chickpea, as compared to dry-pea, lentil, mustard and spring wheat. The following years, canola and wheat were re-cropped on the stubbles of all those five crops to determine the impacts of crop stubbles on water availability and soil profile N in the following spring, and the consequent impact on grain yields of the subsequent crops.

7.1 Water Use Characteristics of chickpea and other pulse crops.

Averaged from two sites in 1997 and 1998, chickpea used 6 to 8 percentage less water than mustard or spring wheat during the growing season when those crops were tested side-by-side (Table 9). Among the three pulse crops, chickpea used more water than dry-pea or lentil. Chickpea conserved an equivalent amount of water as mustard in the soil profile (120 cm depth) after harvest; they were 5 to 7% more than the amount of water that wheat conserved, but were less than those conserved by dry-pea or lentil. Shallow rooting habit of dry-pea and lentil, with the majority of their roots being within the 60-cm depth, had contributed to the greatest water conservation below 60-cm depth in the soil profile.

7.2 Available Water at Planting the Following Spring

Soil water recharge occurred during the winter months and the soil water profile at planting in the following spring was influenced by standing crop stubbles. Adequate amount of available water at spring planting time is the key for a successful crop establishment in the semiarid prairie. This study showed that chickpea stubble had an equivalent amount of available water in the 120-cm soil depth at planting, as mustard or wheat stubbles (Figure 1). The available water on chickpea stubble was less than those on dry-pea and lentil stubbles, which was somewhat consistent with the water status measured after harvest the previous season. Snow retention was probably higher for mustard and wheat stubbles than pulse stubbles; this may have slightly modified the water status in the spring.

Figure 1. Available soil water at planting after five different crop species in 1997 and 1998 (averaged over two sites)

7.3 Grain Yields of Oilseed Crop or Wheat Seeded on Different Stubbles

Averaged on two sites and two years, oilseed crops (canola and/or mustard) produced, on average, a 14% less grain on chickpea stubble than on dry-pea and lentil stubbles (Figure 2). The yield of oilseed crops was 16% higher on chickpea stubble than on wheat stubble. Similarly, spring wheat following those different stubbles showed that wheat grain yield was 20% greater on dry-pea and lentil stubbles than on wheat stubble (Figure 2). The grain yield of wheat was 15% greater on chickpea stubble than on wheat stubble. Wheat had the lowest grain yield when grown on its own stubbles.

A.B.

Figure 2. Grain yield of oilseed crops (A) and spring wheat (B) planted on five different crop stubbles in 1997 and 1998.

7.4 Nitrogen in the Soil Profile at Planting the Following Spring

At planting the following spring, a larger amount of residual N in the soil profile was found in pulse stubble fields than other stubbles as expected (Figure 3). The residual N may have come from two sources; N left in the soil profile after harvest of the previous crops, and N from decomposing crop residues during the period after harvest to the planting the following spring. Pulses have a narrower C:N ratio than mustard or wheat stubbles. The great yield potential in crops following pulses was partially due to the N benefit provided by previous pulse crops.

Among the three pulse crops, chickpea contributed the least residual N measured at planting, with dry-pea being the highest. This is partially due to the C:N ratio of chickpea stubble was relatively higher than those of dry-pea or lentil stubbles. Therefore, it is expected that chickpea will have N benefit to the following crops, but the benefit will not as great as those by growing dry-pea or lentil. This is further supported by the evidence that grain yield of wheat following chickpea was consistently lower than wheat following dry-pea or lentil, but higher than wheat following wheat.

Figure 3. Available N at planting on five different crop stubbles in 1997 and 1998.

8.0 Production Issues with Chickpea: What can we do to minimize the risks associated with late season precipitation and delayed maturity?

Chickpea crops are highly indeterminate - worse than Laird lentil. Chickpea requires drought stress after pod-filling begins in order for the crop to mature on time in our temperate climate. Many management factors can increase the risk of crop failure due to delayed maturity. Careful consideration of risk management factors can greatly improve the chances of successful production of a chickpea crop.

1. Late seeding can lead to late maturity. Seed as early as possible. Late seeding increases the risk of crop failure.

2. Uneven stands can lead to uneven and late maturity. Seed as uniformly as possible. Treat Kabuli seed with Apron to help establish more uniform stands.

3. Ensure that seed is not damaged during seeding, especially for kabulis. Line distributors in air seeders if necessary. Make sure drills can handle large seeds without damaging them.

4. Avoid fields with poor internal drainage. Crops will remain vegetative in low areas where water and nutrients become concentrated. Early season stunting due to excessive moisture can cause late maturity.

5. Chickpea is a deep-rooted pulse, unlike lentil and pea. Seeding on clay soils increases the risk of maintaining and enhancing indeterminate growth. Lighter texture soils will dry out more quickly and more effectively and reduce the risk of crop failure. This is probably the single most effective risk-reducing strategy to avoid late maturity caused by late season precipitation.

6. Avoid soils affected by salinity. Chickpea growth will be delayed by salinity.

7. Avoid sowing on summerfallow, especially outside the brown soil zone areas The extra moisture and nitrogen will increase the risk of late maturity.

8. Avoid soils with high nitrogen concentration. The nitrogen will promote excessive vegetative growth.

9. Growing chickpea in the black soil zones increases the risk of crop failure and poor quality due to late maturity and diseases like ascochyta blight, Sclerotinia stem rot and botrytis gray mold.

10. Use the earliest maturing varieties available. All current varieties were developed elsewhere and most are late maturing for average Saskatchewan conditions. The selection of varieties is limited right now, but earlier maturing varieties (for example, CDC Xena kabuli) are in the pipeline - stay informed if you wish to reduce risk.

11. Avoid improper use of broadleaf herbicides and poor timing of herbicide application. Plan your weed control the year before growing chickpea. Late post-emergent application of broadleaf herbicides like metribuzin will delay maturity.

12. Use good quality seed with no ascochyta infection. Current varieties have early season resistance bet can be set back if conditions are favourable for disease development (cool, wet) in May and June, be prepared to apply fungicide before flowering to protect the crop. Inspect your crop regularly, especially if weather favours the fungus.