7. Integrated Nutrient Management and Integrated Nutrient/ Pest Management

Integrated use of organic and inorganic fertilizer nutrient sources is an ideal that many researchers espouse but which few farmers achieve. The knowledge base for integrated nutrient management is general rather than specific and there is only limited information available on nutrient budgets with different cropping patterns and practices in rice-wheat systems. Return of organic materials to soils is low in many parts of the region because of alternative uses; crop residues are used for animal feed and animal manures are used for fuel. The nutrient contents of manures and composts that are returned to crops are likely to be highly variable and farmers have no way to assess their nutrient content or value. In addition, green manuring is not widely practiced indicating that returns do not justify the effort for most farmers.

Activities in this area are designed to address knowledge gaps and to use a variety of systems approaches to integrated nutrient management. These include use of legume green manures (LGM’s), management of crop residues, and alternative cropping systems and practices. Because adoption of integrated nutrient management practices will probably only occur when multiple benefits are achieved, the research addresses a range of nutrient benefits, direct and indirect, and interactions with pests.

(i) Use of Legume Green Manures

Previous research in the region has evaluated LGM’s only in terms of N and with a few legume species, especially sesbania. Since nitrogen fertilizer is subsidized in most of the countries, there is little incentive for using LGM’s as a fertilizer substitute. Little systematic work has been undertaken to determine the non-nitrogen benefits from a variety of LGM’s or to seek species/practices that target benefits towards specific problems in a particular cropping system. The concept of this knowledge intensive approach is to provide effective options to farmers for fitting LGM’s into different agroecological niches, thereby encouraging adoption. Programs were initiated in Nepal and India. They involve initial screening with candidate LGM species and subsequent evaluation of these in the rice-wheat cropping system.

Nepal

Trials in the mid-hills region with winter legumes were begun in the 1997-98 season and with summer legumes in 1999. The winter season trials were at the research station at Khumaltar in both years and a second trial was carried out at the B deficient Sipaghat site in 1998-99. The summer trials were carried out at the Khumaltar research farm and also in farmer fields in the Kathmandu valley (Bhakatpur) and near Sipaghat (Kavre). The focus to date has been on productivity, disease resistance and nutrient uptake by the different species, which include grain legumes and mustard. Based on results from the winter and summer trials, a more detailed experiment will be designed to assess system-wide effects of a selected subset of legumes within a rice-wheat rotation.

Results

Data from the summer legume trials were variable between sites. With the exception of the Seti soybean cultivar, sunnhemp and pigeonpea, dry matter accumulations at Bhaktapur were below 4.5 t/ha, presumably due to cooler temperatures at this higher elevation. In contrast a majority of the forage type species were above 5 t/ha dry matter at Khumaltar and Kavre. Particularly noteworthy were dry matter production of finger millet, Sesbania cannabina, and Aeschynomene at Kavre, as well as finger millet and Sesbania cannabina at Khumultar. Grain yields were only available for Khumaltar, and seem a bit on the high side, suggesting that the weights may not have been adjusted for moisture content. Noticeable variation was observed within ricebean, soybean, black gram and groundnut cultivars. Ricebean cv. USA, all the soybean cultivars and the Rampur Rahar pigeonpea cultivar appear to offer several particularly promising grain legume options to farmers in this area. Nutrient acquisition between species and sites will be compared after nutrient analysis of the plant materials is complete.

Nutrient concentration and total nutrient uptake by winter legume biomass collected at flowering in Khumaltar varied considerably by legume species (data on the following page). The concentration of most elements was higher in bitter lupin than the other species (especially for K, S, Zn, Mn [note also sweet lupin] and Mo) but a poor stand restricted total nutrient acquisition. However, this species appears to have the potential to extract large amounts of a range of nutrients if agronomic problems to its production can be overcome. With high biomass production, clover species, especially persian clover, had higher total nutrient uptake (kg/ha) for most nutrients than did other species in the trial.

India

An experiment with summer legumes, initiated in May 1996 at Ludhiana (PAU) in India, will complete a fourth year with the current wheat crop. Five legume species (cowpea, mungbean, crotalaria or sunnhemp, clusterbean and sesbania) and one non-legume (bajra or pearl millet) were grown during the 60 day period between wheat and rice crops. Lablab was added in 1997. Soybean was used in 1997 and 1998 and then in 1999 cowpea fodder was substituted in for soybean. Aboveground biomass was incorporated into soil prior to transplanting rice.

Results

Nutrient Acquisition

Nutrient Content of Aboveground Biomass in 60-Day Green Manure Crops

Nitrogen accumulation in above ground biomass was highest with crotalaria and sesbania, then cowpea, mungbean and cluster bean. Considerable N fixation took place if it is assumed that the 20-40 kg N/ha taken up by millet represents available soil N.

Acquisition of other macronutrients and of the micronutrients varied amongst the green manures. Phosphorus concentration ranged between 0.31-0.35% for all species except for crotalaria, which was around 0.21%. At 2.9%, potassium concentration was highest in millet

and ranged from 1.0-1.7% in the legume species. Total nutrient uptake also varied amongst species but crotalaria, cowpea, and sesbania consistently had the highest values for both macro- and micro-nutrients. Manganese uptake (not shown) was highest in crotalaria and cowpea. These differences indicate that much potential exists for tailoring nutrient availability to crops through selection of green manure species.

Differences in nutrient uptake by the various green manures has not been reflected in the nutrient content of the rice or wheat grains or straw. While the LGMs were able to acquire additional macro- and micronutrients, there appeared to be little luxury consumption by the crops. Future plans involve growing crotalaria, cowpea and lablab on several farms with identified nutrient deficiencies throughout the Punjab. Results will be compared with those from the experiment station which likely has more optimal soil nutrient conditions.

(ii) Residue Management

Return of crop residues or additions of farm yard manures (FYM) to soil has declined due to conflicting needs for fodder, fuel, and building materials. Despite these sociological constraints, returning crop residues is critical for regenerating degraded soils. Benefits to soil fertility and physical condition have been documented following long-term crop residue incorporation but several agronomic constraints to the success of this management practice have also been identified. Nitrogen immobilization occurs when rice straw is incorporated prior to wheat cultivation but this is less of a problem with wheat straw, which has time to undergo some decomposition before rice is grown. There may also be allelopathic effects associated with straw incorporation. Farmers with limited mechanization may also find incorporation of straw or other crop residues difficult to achieve. Using straw as a mulch may be a good alternative as at least one experiment with rice-wheat has shown increased yields with this practice.

A field experiment to evaluate alternative crop residue management practices was established at Bhairahawa, Nepal. The experiment was designed as a RCBD with 4 replications and 5 treatments: absolute control, NPK fertilizer only, straw incorporation plus NPK fertilizer, straw incorporation with 20 kg N/ha plus NPK fertilizer, and straw as a mulch plus NPK fertilizer. Wheat straw (1.5 t/ha) was applied before the rice crop and rice straw (3.0 t/ha) was applied before the wheat crop. NPK fertilizer was applied at recommended rates.

Results

In the first year, incorporating wheat straw, significantly increased rice yield relative to the control and NPK fertilizer treatments. This result indicates that straw contributes an added benefit to the crop above NPK, possibly by supplying micronutrients or by positively changing N dynamics and availability in the paddy. Incorporating extra N with straw did not significantly affect rice yield but applying straw as a mulch increased yield over all other treatments.

The reason(s) for the mulch effect is(are) are not completely resolved; possibilities include lowering of floodwater pH and reduced ammonia volatilization in the early stages of rice growth, suppression of weeds, and maintaining soil wetter in the latter part of the season when drought stress may occur. Nitrogen analysis of the first year rice grain and straw are currently underway to determine whether there were any treatment differences in plant N uptake.

We hypothesized that wheat yields might be improved by the rice mulch through weed control and soil moisture conservation. However data from the first year wheat; showed the straw mulch to be equally as beneficial as incorporated straw or only fertilizer, as compared to the control. A second wheat crop is currently in the field.

Measurements of floodwater pH at 40 days after transplanting in the second year rice crop are shown below. The mulch treatment lowered floodwater pH by one pH unit, which would substantially reduce ammonia volatilization. Given the effect of straw incorporation on yield, it seems likely that this treatment also lowered floodwater pH earlier in the season (measurements not made). The mulch treatment appears to have a persistent effect on flood-water pH, which is notable because top dressing of rice with urea usually occurs at 25 and 50 days after transplanting. However this difference in pH did not confer any extra benefit by the mulch treatment in the second year. Despite this result mulching with straw may provide a simple technology to solve one of the major problems in paddy rice production. Collaborative efforts are underway with boro (winter) rice in Bangladesh, to investigate further the role of mulch in lowering the floodwater thereby improving nitrogen use efficiency.

(iii) Alternative Cropping Systems

a) Crop Rotations: More complex crop rotations than rice and wheat may increase yields of the cereals by improving nutrient supply and reducing pest and pathogen pressures. Integrating legumes into the rice-wheat rotation is particularly desirable from both soil quality and human nutrition perspectives. An experiment where a legume crop replaces wheat (lentil) or is grown between rice and wheat as a green manure (crotalaria) or for grain (cowpea) was initiated with the 1998-99 wheat season at the Bhairahawa research station in Nepal. Mustard was also included as a non-legume crop replacement for wheat. The replacement crops are grown for both one and two years.

Data through rice of the second cycle have been gathered. No significant impacts of replacement or break crops have been recorded, except in the second rice crop after the crotalaria green manure. As is typical after a green manure, rice yields increased by 1.25 t/ha (30%). Pathogen data have been recorded from the plots but were not available for this report. Soils from the experiment are currently undergoing nutrient analysis.

b) Mungbean Relay: Mungbean is an increasingly popular, high value cash crop in Shankarchandra, a village in Chuadanga district, Bangladesh. Mungbean is normally planted after wheat harvest; however sowing after March 15th usually leads to reduced seed yield. Relay seeding mungbean into standing wheat could achieve more timely establishment. Initial experiments were conducted on farm fields in Chuadanga district and at the Joydebpur research station in 1998 to evaluate the productivity of wheat and mungbean when mungbean is relayed into wheat at 15 and 7 days before wheat harvest and at wheat harvest. There were no adverse impacts on wheat production, but as expected mungbean yields decreased with later relay planting dates, while above-ground biomass showed a reverse trend with planting dates.

Despite the potential for fitting mungbean into this system, mungbean yields have been very low. Possible explanations for the poor yields are micronutrient (boron) deficiency or selection of an inappropriate mungbean variety. With these possibilities in mind, the mungbean experiments at Joydebpur and Chuadanga were repeated in 1999 with and without micronutrient treatments. Micronutrients had not effect and again yields at both sites were very low (Joydebpur - 0.060 t/ha; Chuadanga - 0.22 t/ha).

Observations from these experiments and mungbean breeding trials at Joydebpur suggest that the currently recommended indeterminant, long duration varieties may not be appropriate for this application. Shifting to determinant, shorter duration varieties might help to increase productivity. One possibility is the 60-day variety, with 2 ton/ha yield potential, developed by the Asian Vegetable Research and Development Center (AVRDC), now that it has resistance to yellow mosaic virus. Efforts are underway to foster more collaboration with scientists at the Pulse Research Center at Ishurdi, Bangladesh.

II. Soil Acidity

Acid soils are found mainly in the eastern part of the Indo-Gangetic Plain, i.e. in West Bengal, Bangladesh and the mid-hills region of Nepal, where cropping is intensive and monsoonal precipitation is high. In many of these soils, organic matter is also quite low, resulting in poor buffering capacity and low nutrient contents. Liming of soils is not practiced. In a previous experiment at Dinajpur, application of 3 t lime/ha increased wheat yields by 33%, most likely because of increased P availability at higher pH’s. However, micronutrient availability (B, Zn, Cu, Mn) will be reduced at higher pH, potentially inducing micronutrient deficiencies. For example we demonstrated that liming increased sterility and reduced wheat yields by exacerbating an existing soil B deficiency at Sipaghat in Nepal. Given that the micronutrient status of many soils in the Dinajpur area is poor, research was initiated to investigate the effect of liming soil on the productivity of rice and wheat and to determine whether there are interactions between liming and micronutrient availability.

Effects of Liming and Interactions with Micronutrients

Two experiments were initiated in Dinajpur district in northwest Bangladesh in the 1999 rice season. One was on-farm (Birgani thanna) and one was on the research station at Nashipur. The soils at these sites range in pH from 4.9 to 5.1 and lime was added at 1.1 t/ha to raise soil pH to 5.6-5.8. An "overliming" treatment at 2.2 t/ha was also included to determine whether this would induce any micronutrient deficiencies. Zinc availability is known to be marginal in the area and we have previously identified Zn deficiency in wheat. Lime was applied prior to transplanting rice to ensure adequate reaction time before the following wheat crop. Flooding during the rice season causes soil pH to rise to about 7, so lime is not expected to alter soil pH in the rice paddy. Both experiments included 3 lime levels (0,1.1, and 2.2 t/ha) and a basic suite of nutrient treatments; N, NKS, NPKS, and NPKSMg. The on-farm experiment had an additional treatment, NPKSMgZnB, where Zn and B were soil applied prior to planting. Plots on station were split, with half receiving foliar applications of micronutrients and half not. There were 3 replications of each treatment in each experiment. BR-32 rice, which is susceptible to micronutrient deficiencies, was transplanted in these experiments and Kanchan is the wheat variety.

Results

A strong response to liming was seen at both sites and liming did not induce any micronutrient deficiencies. Yield was increased up to 27% and by 10% with liming on the farm and research station, respectively. A response to P (0.56 t/ha, 14%), but not K,S, or Mg was observed on the farm. Interactions between nutrient sources and lime were observed on the research station but not on the farm. Without lime, yield responses to P and K or S were found but not Mg; the combined response was 1.2 t/ha or 28%. An 8% yield response to K or S and no response to P or Mg was found at the low lime rate. An 8% yield increase, attributable to P, was found at the high lime rate. Soil pH and nutrient content after rice harvest and lime analysis are pending.

III. Soil Degradation

A. Physical

Puddling of soils for rice production destroys soil aggregates and creates pans that can restrict root penetration. Although puddling is generally considered beneficial for rice, the poor soil structure that it creates interferes with the timely establishment of wheat and often leads to poor crop stands and growth. There is also interest in direct seeding of rice because of projected labor shortages for transplanting. These factors led us to implement tillage experiments to improve the soil environment for wheat and to include different plant establishment techniques for both rice and wheat.

(i) Tillage Experiment 1

This experiment is a split-split plot design with three replications. It consists of two tillage practices prior to rice (deep and normal), two rice crop establishment techniques (puddling and transplanting, and direct seeding with rotovator/drill attachments to a Chinese tractor) and two wheat establishment techniques applied to each rice plot (surface seeding without tillage, and Chinese rotovator/seed drill). The deep tillage consists of deep ripping (50 cm deep on 50 cm centers) followed by two passes with a cultivator. Normal tillage consists of two passes with the cultivator. The experiment is established at NARC research stations at Bhairahawa and Khumaltar. Because weed pressure is a likely constraint with direct seeding, a 3m deep strip across each plot is left unweeded to assess crop loss if no control measures were used (Bhairahawa site only).

Results - Bhairahawa

NT = normal tillage; DT = deep tillage; TPR = transplanted rice; DSR = direct seeded rice;

CSD = wheat planted by Chinese Seed drill; SS = surface seeding of wheat

* No previous wheat tillage treatments

2 see complete statistical analysis

1 values followed by the same letter are significantly different at p < 0.5

 

At Bhairahawa, no significant effects of tillage and crop establishment methods on rice yields have been found to date. Surface seeding of wheat immediately after the first rice crop almost doubled crop yields compared to the conventional tillage/drill establishment treatment. This was because rainfall delayed land preparation and conventional wheat planting by 40 days. However, no effect of the rice tillage treatments was seen in the first wheat crop. In contrast to the first year, yields of the second wheat crop were not significantly affected by establishment technique but were significantly higher (p<0.005) with the deep tillage treatment.

In contrast to expectations, weed pressure was not significantly higher with direct seeded rice, probably because plots were flooded most of the time. Fewer weeds were present in surface seeded wheat than with the conventional practice. Wheat yields in the weedy check (no weeding) were reduced by an average of 2.9% with surface seeding and 10.8% with conventional practice.

Results-Khumaltar

The experiment was begun with the 1997-98 wheat season with deep tillage prior to seeding, then again prior to rice. There were no significant effects of tillage or establishment method on yield (mean 2.9 t/ha) with the first wheat crop. However, surface seeding suppressed both grassy and broadleaf weeds and gave more tillers per plant. Also, deep tillage gave greater plant biomass. Possibly these differences did not translate into yield differences because of late planting (Nov 29). Similarly, there were no effects of the treatments on rice yield (mean 6.1 t/ha) in 1998. The experiment has continued through to the present, but data is not available because of several management changes. We anticipate retrieving the data in the near future.

(ii) Tillage Experiment 2

This experiment at Khumaltar, Nepal was carried out for 2 years as part of the PhD thesis research of Medha Devare. It explored the effects of deep tillage, water management in rice (grown as paddy or "upland" crop), intercopping rice with blackgram, and solarization on productivity of rice and wheat. The experiment began with the 1997 rice crop and several problems led to low yields of rice in the unflooded and intercrop treatments.

Following the rice crop a deep tillage treatment (same as tillage experiment 1) was done prior to wheat. This treatment significantly (p<0.05) increased wheat yield from an average of 3.0 t/ha to 4.7 t/ha. The design of the experiment was then modified for the second rice-wheat cycle to include sub-plots which were solarized and a deep tillage treatment was again imposed prior to rice.

With puddling, tillage had no effect on rice yields. Yields in the non-puddled plots were comparable to those in puddled plots with deep tillage, but were reduced by 1.6 - 1.7 t/ha (30 - 54%) with normal tillage. Solarization increased rice yields by an average of 43% to a high of 8.0 t/ha. Results from this experiment are complicated by differences in depth to water table across the site. Soil-plant-water relationships are being analyzed in order to more fully interpret the data. In addition root morphology, pathogen incidence and economic factors will be addressed in a dissertation currently underway.

1 NS = non-solarized; S = solarized

Another Ph.D. thesis was started during summer 1999 at the same site as Tillage Experiment 2, in order to address the influence of tillage and crop establishment on water relations as well as productivity in rice-wheat. This work is being done by Andrew McDonald and involves three types of tillage before rice: shallow (conventional); deep tillage by subsoiler; and deep tillage plus moldboard plowing. Within each tillage regime, rice was either transplanted after puddling or direct seeded into unpuddled soil. Imposing the treatments perpendicular to the natural hydrologic gradient, mentioned above, allowed for additional comparison of relative lowland and upland areas commonly found in the mid hills of Nepal. In addition to yields and weed pressure, seepage and percolation rates were monitored throughout the rice season. Impacts of the rice tillage-crop establishment treatments are currently being measured during the wheat season.

B. Biological

Soil biology is an under researched area of soil science. Our knowledge of micro-flora and faunal species and communities, their functions, and how to manipulate this soil biological ecosystem for the benefit of crop production is limited to a few situations. In a simple crop rotation like rice and wheat, it is likely that populations of organisms that are detrimental to root health have built up in the soil with consequent negative impacts on crop yield. To evaluate this hypothesis, we have carried out surveys of soil borne pathogens and a large number of diagnostic solarization trials.

Our initial work started with solarization, the heating of soil by covering it with clear plastic, to determine the extent to which soil biology/soil borne pathogens limit yields of rice and wheat, or conversely the yield gains that could be realized if these "soil biological" problems could be overcome. We first demonstrated the effects of soil solarization at research centers, then on farmer fields. Solarization impacts on increasing rice yields ranged from 0.5 to 3.0 t/ha (15 to 70% increase over the control); while wheat yields following solarization were 0.4 to 0.7 t/ha higher than wheat from nonsolarized plots. In general the results demonstrate that yield potential is almost always increased, but not always achieved with solarization, because of increased insect pressure or lodging.

1. Mechanisms of Solarization Response

Nepal

Given the positive results with solarization, subsequent studies focussed more on determining the specific constraints overcome by solarization. One experiment on the NARC station at Bhairahawa, Nepal compared the effects of residual solarization in wheat with several chemical treatments having differing pathogen targets. Main plots included solarization before rice and Furadan, a soil insecticide/ nematicide before wheat. Seed treatment with and without Vitavax formed the subplots; and sprays with and without Tilt, to control foliar diseases, are the sub-sub plot treatments.

*, **, *** indicates statistical significance at the p < 0.05. 0.01 and 0.001 levels, respectively

No statistically significant interactions measured

The 1998-99 wheat results show equal yield benefits (17% increase) with solarization and Furadan, suggesting that constraints to production in this case were dominated by soil biology factors. Vitavax seed treatment had positive effects on seedling emergence and negative effects on Helminthosporium leaf blight, but the lack of an impact on yield implies that pressure from seedborne pathogens was less than other factors. Clean and healthy seeds from the research station may have had a significant contribution. Tilt spray was effective in reducing post-infection pathogenic fungi and gave similar yields to the solarized and Furadan treatments. Overall the results point to soilborne pathogenic fungi and nematodes (controlled by Furadan) as the constraint factors involved during wheat 98-99.

Before rice 1999, the soil again was solarized. Fungal populations and rice root nematode infection on rice roots were sampled before and after solarization. Pathogenicity tests are currently ongoing to quantify the impact of solarization on pathogenic fungi. As for the rice root nematode, solarization reduced its populations from 49 /g rice root to 9 /g rice root; however, in the soil, the previous Furadan treatment (before wheat 1998-99) seemed to have a residual effect. Rice root nematodes in the control soils were 80/L versus 28 /L in the Furadan treatment and 10 /L in the solarized plots. Unfortunately yield data are not available for reporting at this time. Another crop cycle with wheat is currently ongoing.

 

Bangladesh

 

Two experiments were undertaken in Bangladesh to evaluate the effects of Vitavax seed treatment and/or solarizing rice nurseries. (i) Treatments included combinations of: ± solarized seedlings and ± Vitavax treated seeds which were placed inside ± solarized main plots. This experiment was carried out on a farmer field at Chuadanga.

Results

Yields from the solarized main beds were not that much different from the unsolarized plots, suggesting that either solarization was not effective or that insect damage/lodging occurred in the solarized plots, thereby reducing yields. As such it is difficult to evaluate the specific production constraints (if any) operating in the main fields at this site

However in comparing the results from seedling solarization and seed treatment, we find that Vitavax applied to rice seed without any solarizations increased rice yields by 0.57 t/ha (14%) relative to the complete control. Solarized seedling treatments without Vitavax performed similarly to Vitavax alone, implying the two treatments were addressing the same production constraint, soilborne pathogens. It should be noted that BRRI scientists do not recommend seed treatment for rice. However the results from this experiment indicate that either Vitavax or nursery solarization has a significant advantage for farmers.

In addition to the previous experiment, a trial was undertaken on-station at Nashipur, Bangladesh to evaluate the impact of rice seedling bed solarization. (ii) Treatments included ± solarized seedlings and ± solarized main beds.

On average seedling bed solarization at this site increased yields by 0.28 t/ha (7% over the control). Solarizing main beds had a much bigger impact than seedling solarization, possibly because a micronutrient deficiency existed with this variety (BR32). Nevertheless, the impacts of solarized seedling beds may vary from site to site. We recognize that field scale solarization is not a practical nor an environmentally sound practice to advocate to rice -wheat farmers. However potential practical applications for solarization at the farm level could be for rice seedling nurseries or vegetable production. Future efforts will concentrate on evaluating solarized rice seedling beds as well as Vitavax seed treatment, using farmer participatory approaches in the Dinajpur and Joydebpur areas.

Research work for a Ph.D. thesis by Jon Padgham has just started in Bangladesh. The objectives of the planned research are (i) to further our understanding of causes for the dramatic effects of soil solarization on rice and wheat productivity and (ii) to evaluate the role of production and use of residues from cowpea and mungbean on soil biological constraints to rice and wheat productivity. The research will develop and use in vitro simulated solarization together with seedling bioassays to screen the impacts of solarization on a range of soils. Mechanisms of the solarization effect will then be investigated in "good" and "bad" soils. Finally, the impact of introducing cowpea and mungbean into the rice-wheat system on soil borne pathogens will be evaluated and compared with solarization using in vitro and field approaches.

2. Pathology Surveys

Pathology surveys were initiated in Dinajpur and Gazipur districts, Bangladesh and Rupandehi and Naldung districts, Nepal to evaluate the prevalence of soilborne pathogens in rice-wheat fields. "Normal/Good" and "Declining/Poor" rice-wheat fields were identified based on farmer observations. All sites were geo-referenced for later use with GIS. Plant roots and soils were sampled during 1998 rice, 1998-99 wheat and 1999 rice.

Despite the best efforts of all participants in these initial surveys, it became clear that additional training in methodology and identification was necessary. Hands-on workshops were conducted in September 1999 by Drs. George Abawi and Tim Widmer at Joydebpur, Bangladesh and Rampur, Nepal. A procedures manual was developed by Drs. Abawi and Widmer and distributed to the participants.

.

Results from surveys show that on average in Bangladesh, there are twice as many identifiable parasitic nematodes in wheat (643/100g soil) as in rice (386/ 100g soil). Of the wheat parasitic nematodes, Meloidogyne (root-knot nematode) dominate (72%), followed by Tylenchorynchus (15%; stunt nematode). In the rice soils of Dinajpur, 53% of the total counts were Tylenchorynchus with only 16% as Hirschmaniella. (rice root nematode). Nematode counts from the Nepali sites are substantially lower than the Bangladesh sites (0.3-1.9/100g soil). Hirschmaniella dominated the counts, especially in heavier textured soils. The unexpected low nematode counts in Nepal may be due to sampling time, extraction techniques or other factors. Optimal sampling time for rice root nematode is at maximum tillering; however most of the Nepal and Bangladesh samples have been taken at late flowering.

Fungi isolated from discolored crop root segments revealed Fusarium on 45-64%; Bipolaris sorokiana on 8-18% and Curvalaria on 6-26% of the wheat roots collected from Gazipur and Dinajpur, Bangladesh. Rice roots were about equally infected with Curvalaria (16%), Fusarium (11%) and Phoma (12%). Discolored/unhealthy wheat roots collected from 37 farms in the terai of Nepal were cultured into three groups: Fusarium spp. (38%), Bipolaris sorokiniana (11%) and Curvalaria (5%). Similarly in the mid-hills, 56% were Fusarium spp., followed by Curvalaria at 10% frequency. Rice roots were dominated by Chetomium (62%) at one site in Naldung and Curvalaria (44%) at Sipaghat. Otherwise Fusarium and Alternaria were found in all samples, ranging in frequency from 21-46% (Fusarium) and 12-37% (Alternaria). Pathogenicity tests are being performed on isolates brought to Cornell, especially the Fusarium which seems to be ubiquitous, but not always pathogenic.

IV. Socio-Economic Activities

Two representative villages were selected in rice-wheat areas of Bangladesh (Sankarchandra, and Jagdal). Initially Participatory Rural Appraisals (PRA) were conducted in an effort to foster multi-disciplinary, multi-institutional interactions and to gather basic information from these villages. Subsequently more detailed diagnostic surveys were carried out during both rice and wheat seasons to further characterize farmer practices, socioeconomic conditions and perceived constraints.

Two villages in northwest Bangladesh (Jagdal and Haldibari in Dinajpur and Rangpur districts, respectively) have been selected for detailed studies. Biophysical and socio-economic surveys have provided baseline characterizations of the villages and a series of food systems and human nutrition surveys are nearing completion. These data bases will be utilized in economic analyses linking household decision making processes to food security and income generation opportunities (PhD thesis of Kaaffe Billah) and food systems analyses linking soil fertility to food quality and household nutrition and health (PhD thesis of Anne Marie Mayer).

A more classical economic analysis has just been completed for Sankarchandra village in Chuadanga, Bangladesh. Resource productivity functions were constructed for transplanted aman (T. aman) and boro rice as well as wheat. For T. aman, insecticide expenses, use of manure, irrigation and tenure status had significant contributions on rice production. Not surprisingly, tenure status had a negative effect on T. aman cultivation, indicating tenant farmers were less productive than owner farmers. For boro rice, labor, power tiller use, insecticides , seed and farm size significantly effected productivity. Farm size had a negative effect, in that larger farms had lower marginal productivity than smaller farms. Wheat productivity was determined by more than 10 different variables, except power tiller use. Labor was found to have a negative impact on wheat production, which implied that farmers needed to reduce labor use to make wheat production more profitable. Perhaps the power tiller could help in reducing the excess labor.

A survey and analysis of 50 farmers in Dinajpur/Rangpur were recently completed for 1998-99 wheat to quantify the economic and agronomic gains to farmer using the Chinese power tiller-cum-seeder (CPTS). This improved technology is already available to farmers and is a excellent option for reducing the turn-around-time (TAT) between rice and wheat, a major constraint to good wheat yields. A comparison of 25 farmers using CPTS with 25 using the conventional country plow showed that TAT was reduced from 7-12 days to 1 day with CPTS. Seeding rates (148 vs. 210 kg/ha) and irrigation (2 vs 3) were also reduced with CPTS. Due to better and more consistent seed placement, CPTS farmers obtained 20% higher yields than conventional farmers. As a result of all these factors, CPTS farmers obtained an additional Tk 5860 (~$ 114) in gross margin.

V. Related Activities

A. Additional Surveys - Weeds and insects have been identified by the NARS as additional constraints to increased rice-wheat production in S. Asia. Quantifying the magnitude and geographical extent of these constraints as well as identifying possible connections with soil management practices is an important goal of Cornell’s program.

(i) Weeds: a survey was undertaken in 9 districts of Nepal, with special attention to the incidence of Phalaris minor. Results from the survey were summarized in the 1998-99 Annual report. In addition a 65 page report was completed and published by NARC and the SM-CRSP in May 1999 (see Publications). Copies were distributed to the RWC Facilitation unit and to NARS groups in Bangladesh, India and Pakistan.

Additional weed data were collected in 1999 in Rauthat and Parsa districts of the eastern Terai region, to provide baseline information for long term monitoring farms in the Parwanipur area, one of four research sites in Nepal. On 49 farmer plots, the dominant wheat weeds were consistently Chenopodium album, Polypogon fugox and Polygonum plebijum. Phalaris minor was found on 12 out of 49 plots, but at low to medium populations (4 -32% of sampling quadrate).

A new tillage management strategy recently developed by CIMMYT-Mexico (bed-planting) is particularly effective at controlling P. minor . Future efforts will focus on adapting bed-planting to the environmental and management constraints of S. Asian farmers.

ii) Insects: surveys were carried out in Bangladesh where farmers routinely use pesticides in rice (2-3 sprays) but not in wheat. Based on two years survey data, shoot fly, wire worm and stem borer were found to be the dominant insect pests identified in wheat across 7 districts of Bangladesh. However infestation rates by these insects were quite low ranging from 0 to 7.8%.

Earlier survey results suggested that wire worm infestation might be associated with FYM/dung use. A study to evaluate different levels of FYM on wire worm incidence was conducted during the1998-99 wheat season. No significant effects were found between FYM and untreated plots, presumably because of low wire worm population levels.

Rice insect pests were surveyed at 10 farms in each of 5 districts of Bangladesh during the 1999 panicle initiation phase. On average green leaf hopper, grasshopper, and leaf roller dominated at all sites in sufficiently high numbers (62, 21 and 18/20 sweeps, respectively). Weak negative relationships between spiders and grasshoppers as well as between damsel flies and leaf rollers were also observed. No associations between soil management practices and rice pest incidence were found.

B. Technology Adoption

(i) Information Systems - The rapidly, expanding technology of Geographical Information Systems (GIS) can be used to determine extrapolation areas of natural and human resources, to evaluate relationships between variables and, when coupled with crop modeling, to evaluate alternative management or production scenarios.

Bangladesh and Nepal GIS groups currently have adequate hardware and software to do GIS work. Quite a few maps have been constructed in Bangladesh, but are currently unavailable for display. Data obtained from the various soil, pathology, insect, weed, sterility surveys and experiments are being shared with the respective GIS groups for making maps.

(ii) Farmer demonstrations - Based on positive feedback from 1997-98 demonstrations in Bangladesh and Nepal, new areas were targeted to illustrate use of a drill attachment for the Chinese hand tractor (CHT) and wheat surface seeding technologies. Forty-one farmers from Chuadanga, Bangladesh participated in trials comparing the CHT drill with normal land preparation and planting. On average use of the CHT drill increased wheat yields by 16-22% over normal practice. A cost-benefit analysis on three of the farms also demonstrated a Taka 7029 (~$140) advantage to the CHT over normal practice.

Demonstrations of surface seeding of wheat on 8 farmer fields in Parwanipur, Nepal in 1998-99 gave an average grain yield of 2.2 t/ha from low lying fields that normally lay fallow during winter. Participatory approaches will be used during the 1999-2000 wheat season to extend surface seeding to more farmers in the Parwanipur area. We also plan to evaluate the adoption of surface seeding in the Rupandehi district of Nepal.

C. Human Resource Development

The following training/NARS enhancement opportunities were supported by the SM-CRSP during Project Year 3:

• S.P. Banu (BARI), H.U. Ahmed (BRRI), R.R. Pokhrel (IAAS) and R.P. Upreti (NARC) attended the second Nematology Workshop of the Rice-Wheat Consortium in New Delhi, India April 1999.
• S. Rawat and S. Chaudhary (NARC) attended a specially arranged training at Punjab Agricultural University to upgrade their soil nutrient analysis capabilities. July-August 1999.
• Drs. G. Panaullah, Nur E.-Elahi (BRRI), Mr. M. Saifuzzaman and Mr. A. Rahman (BARI) participated as regional collaborators during the annual project review in Nepal. January 2000.

D. Publications

Duxbury, J.M., I.P. Abrol, R. Gupta, and K.R. Bronson. 2000. Analysis of long-term soil fertility experiments with rice-wheat rotations in South Asia. Rice-Wheat Consortium & SM-CRSP publication. (In press).

Hobbs, P.R., Y.Singh, G.S.Giri, J.G. Lauren and J.M. Duxbury. 2000. Direct seeding and reduced tillage options in the rice-wheat systems of the Indo-Gangetic Plains of South Asia. Proc. Int. Rice Res. Instit. Workshop 'Direct Seeding in Asian Rice Systems.' Bangkok, Thailand. 25-28 January 2000. (In review).

Ranjit, J. N.K. Rajbhandari, R. Belinder, and P.K.K. Kataki. 1999. Mapping Phalaris minor in rice-wheat cropping system of different agroecological regions of Nepal. Nepal Agric. Res. Council and Soil Management CRSP-Cornell Univ. 65p.

Singh, Yadvinder, Bijay Singh, J.G. Lauren, and J.M. Duxbury. 2000. Crop residue management for rice-based cropping systems of the tropics. Adv. Agron. (In review.)

Widmer, T. and G. Abawi. 1999. Procedure manual for rice-wheat sampling and processing in Nepal and Bangladesh. Training tool.

VI. Collaborators

A. Country

C. Other Collaborating Organizations

1 Institute of Agriculture and Animal Science

Seven students have entered the graduate program at Cornell University with at least some funding from the SM-CRSP rice-wheat project. One has graduated, one is writing her thesis, three are currently carrying out thesis research, and two are completing coursework and planning thesis research.

The SM-CRSP rice-wheat project has also agreed to fund four MS degree level students at the Institute of Agriculture and Animal Science (IAAS) at Rampur, Nepal. IAAS is the agricultural college of Tribuhvan University. We expect to maintain from 2-4 students in the MS program for the duration of the project. The two year MS degree program is new and costs to us for fees and student support are about $1250/yr/student. The Institute has agreed to waive overhead costs and fees that it normally charges students who have external support. Three students have been identified for this program and a fourth student will be identified this next academic year. Faculty at IAAS have formalized a multi-disciplinary rice-wheat research group, comprised of 2 pathologists, 3 agronomists and one soil scientist.

VII. Acronym Definitions

BRRI Bangladesh Rice Research Institute

BARI Bangladesh Agriculture Research Institute

CIMMYT International Center for Maize and Wheat

IAAS Institute for Agriculture and Animal Science

IARC International Agricultural Research Centers

ICAR Indian Council of Agricultural Research

ICRISAT International Center for Research in the Semi-Arid Tropics

IGP Indo- Gangetic Plains

IRRI International Rice Research Institute

NARC Nepal Agriculture Research Council

NARS National Agricultural Research Scientists

PAU Punjab Agricultural University, Ludhiana, India

RWC Rice Wheat Consortium