Piara Singh

Influence of water-deficits on phenology, growth and dry-matter allocation in chickpea (Cicer arietinum)☆

Abstract Quantitative understanding of the response of phenology and crop growth to environmental factors is required to build yield-prediction models. Field experiments were conducted to study the influence of water-deficits on phenology, growth and dry-matter allocation in chickpea ( Cicer arietinum L., cv. JG 74). The crop was subjected to increasing intensities of water deficits during both vegetative and reproductive phases by applying gradient irrigations. Durations of emergence to flowering ( e-fl ), flowering to beginning of pod-fill ( fl-bpf ), and beginning of pod-fill to physiological maturity ( bpf - PM) were inversely correlated with normalized evapotranspiration-deficit ( E t -deficit) experienced by the crop during a growth period. In terms of thermal time (base temperature=8°C, ceiling temperature = 30°C), the durations of e-fl, fl-bpf , and bpf-pm phases decreased by 4.5, 3.1, and 3.8°Cd for each mm kPa −1 of normalized E t -deficit, respectively. Water-deficits prior to flowering decreased canopy development, light interception, and dry-matter production to the maximum extent compared with stress after flowering. Water-deficit prior to pod-initiation did not influence the allocation of dry-matter between leaves and branches, but water-deficit during the reproductive phase increased allocation to the reproductive organs. Normalized E t -deficit of 1 mm kPa −1 increased allocation to the pods by 0.75% of the biomass produced after pod-initiation and to the seeds by 0.52% of the biomass produced after bpf . It is concluded from this study that we need to consider the influence of water stress on phenology, growth and dry-matter allocation in chickpea in addition to other environmental factors affecting these processes.

Modeling growth and yield of chickpea (Cicer arietinum L.)

Abstract A chickpea (Cicer arietinum L.) growth and development model ( chikpgro ) has been developed from the hedgerowversion of the groundnut model pnutgro . Changes were made in various subroutines determining vegetative and reproductive development, crop growth and partitioning of assimilates to component plant organs to simulate chickpea crop growth under water-limiting and nonlimiting situations. Using the experimental data of the 1984 and 1986 seasons, the model was calibrated for cultivar-specific parameters of cvs. Annigeri and JG 74 and also for soil parameters determining water balance of the root-zone. The model was validated against data from the 1985, 1987, 1992 and 1993 seasons. The model predicted flowering, pod initiation, beginning of seed growth and physiological maturity within ± 5 days of the observed values, except under extreme wet situations when the actual seed growth and physiological maturity of chickpea occurred later than the simulated dates. Leaf area index, total dry matter production (TDM) and its partitioning to various plant organs under irrigated and water-stressed conditions were also predicted satisfactorily by the model. Soil moisture changes in the rooting-zone of chickpea were also predicted accurately. Predicted TDM and seed yields of cvs. Annigeri and JG 74 at harvest were significantly correlated with the observed data (r2 = 0.89 and RMSE = 0.34 t/ha for TDM; r2 = 0.82 and RMSE = 0.14 t/ha for seed). These results show that chikpgro can be used to predict potential and water-limited yields of chickpea in the Indian plateau. Future work requires inclusion of a soil fertility submodel and model testing over a wide range of environments.

Evaluation of the groundnut model PNUTGRO for crop response to water availability, sowing dates, and seasons

Field experiments were conducted during the 1987, 1991 and 1992 rainy seasons at Patancheru (latitude 17°32′N; longitude 78°16′E; elevation 545 m), Andhra Pradesh, India, to collect data to test and validate the hedgerow version of the groundnut model PNUTGRO for predicting phenological development, light interception, canopy growth, dry matter production, pod and seed yields of groundnut (Arachis hypogaea L.) as influenced by row spacing and plant population. The model was calibrated using the crop growth and phenology data of groundnut (cv. Robut 33-1) obtained from the 1987 and 1991 rainy season experiments. In these experiments groundnut was grown at plant populations ranging from 5 to 45 plants/m2 with and without irrigation. Changes were made in the cultivar-specific coefficients related to the light penetration into the crop canopy and dry matter production. The model was validated against independent data obtained from a 1992 rainy season experiment. In 1992, groundnut was grown at plant populations ranging from 10 to 40 plants/m2 and at row spacings of 20, 30 and 60 cm. The model predicted the occurrence of vegetative and reproductive stages, canopy development, total dry matter production and its partitioning to pods and seed accurately. Maximum leaf area index observed during the season was significantly correlated with simulated values (r2 = 0.95). In spite of some incidence of diseases and pests, the correlation between simulated and observed pod yield was significant (r2 = 0.61). It is concluded from this study that the hedgerow version of the groundnut model PNUTGRO can be used to quantify groundnut growth and yields as influenced by plant population and row spacing.

Influence of water deficit on transpiration and radiation use efficiency of chickpea (Cicer arietinum L.)

Information on the relationship between biomass production, radiation use and water use of chickpea (Cicer arietinum L.) is essential to estimate biomass production in different water regimes. Experiments were conducted during three post-rainy seasons on a Vertisol (a typic pallustert) to study the effect of water deficits on radiation use, radiation use efficiency (RUE), transpiration and transpiration efficiency (TE) of chickpea. Different levels of soil water availability were created, either by having irrigated and non-irrigated plots or using a line source. Biomass production was linearly related to both cumulative intercepted solar radiation and transpiration in both well watered and water deficit treatments. Soil water availability did not affect RUE (total dry matter produced per unit of solar radiation interception) when at least 30% of extractable soil water (ESW) was present in the rooting zone, but below 30% ESW, RUE decreased linearly with the decrease in soil water content. RUE was also significantly correlated (R2 = 0.61, P < 0.01) with the ratio of actual to potential transpiration (T/Tp) and it declined curvilinearly with the decrease in T/Tp. TE decreased with the increase in saturation deficit (SD) of air. Normalization of TE with SD gave a conservative value of 4.8 g kPa kg−1. To estimate biomass production of chickpea in different environments, we need to account for the effect of plant water deficits on RUE in a radiation-based model and the effect of SD on TE in a transpiration-based model.

Evaluation of the groundnut model PNUTGRO for crop response to plant population and row spacing

Field experiments were conducted during the 1987, 1991 and 1992 rainy seasons at Patancheru, Andhra Pradesh, to collect data to test and validate the hedgerow version of the groundnut model PNUTGRO for predicting phenological development, light interception, canopy growth, DM production, pod and seed yields of groundnuts as influenced by row spacing and plant population. The model was calibrated using the crop growth and phenology data of groundnut cv. Robut 33-1 obtained from the 1987 and 1991 rainy season experiments. Groundnuts were grown at plant populations ranging from 5 to 45 plants/sq m with and without irrigation. Changes were made in the cultivar-specific coefficients related to the light penetration into the crop canopy and DM production. The model was validated against independent data obtained from a 1992 rainy season experiment. In 1992, groundnuts were grown at plant populations ranging from 10 to 40 plants/sq m and at row spacings of 20, 30 and 60 cm. The model predicted the occurrence of vegetative and reproductive stages, canopy development, total DM production and its partitioning to pods and seed accurately. Maximum LAI observed during the season was significantly correlated with simulated values (sq r = 0.95). In spite of some incidence of diseases and pests, the correlation between simulated and observed pod yield was significant (sq r = 0.61). It is concluded that the hedgerow version of the groundnut model PNUTGRO can be used to quantify groundnut growth and yields as influenced by plant population and row spacing

Control of Water Use by Pearl Millet (Pennisetum typhoides)

At Hyderabad, India, stands of pearl millet were grown after the monsoon (a) with no irrigation after establishment and (b) with irrigation as needed to avoid stress. Increases of dry matter and leaf area were determined by regular harvesting. The interception of radiation by the foliage, uptake of water from the soil and stomatal conductance were monitored. Before anthesis at 42 days after sowing (DAS), the rate of dry matter production and the transpiration rate in the unirrigated stand were about 80% of the corresponding rates for the irrigated control, mainly because of a smaller stomatal conductance from 30 DAS. After anthesis, the unirrigated stand grew little and used only 10% of the water transpired by the control. This large difference was partitioned between loss of leaf area and smaller stomatal conductance in the ratio of approximately 2:1. Radiation intercepted by foliage in the irrigated stand produced 2.0 g of dry matter per MJ compared with 2.5 g MJ−1 for the same variety growing in the monsoon, a difference consistent with a smaller stomatal conductance in drier air

Soybean–chickpea rotation on Vertic Inceptisols: I. Effect of soil depth and landform on light interception, water balance and crop yields

During 1995-1997 a field study was conducted at the ICRISAT Centre, Patancheru, Andhra Pradesh, India, on a Vertic Inceptisol watershed to study the effect of two soil depths, shallow (<50 cm soil depth) and medium-deep (=50 cm soil depth), and two landform treatments, flat and broadbed-and-furrow (BBF) systems, on productivity and resource-use efficiency of a soyabeans-chickpeas rotation. Soyabeans grown on flat landform on medium-deep soil had a higher leaf area index and more light interception compared with the soyabeans grown on the BBF landform. This resulted in an increase in mean seed yield for the flat landform (2.12 t/ha) compared with the BBF landform (1.87 t/ha). However, the landform treatments on shallow soil did not affect soyabean yields. The soyabean yield was higher on the medium-deep soil (1.76 t/ha) than on the shallow soil (1.55 t/ha) during 1995-1996, but were not different during 1996-1997. In both years chickpea yields and total system productivity (soyabean + chickpea yields) were greater on medium-deep soil than on the shallow soil. Total run-off was higher on the flat landform (25% of seasonal rainfall) than on the BBF landform (20% of seasonal rainfall). This concomitantly increased profile water content (10-30 mm) of both soils in BBF compared with the flat landform treatment during 1995-1996, but not during 1996-1997. Deep drainage was higher in the BBF landform than in flat, especially for the shallow soil. Across landforms and soil depths, water use (evapotranspiration) by soyabeans-chickpeas rotation during 1996-1997 ranged from 496 to 563 mm, which accounted for 54-61% of the rainfall. These results indicate that while the BBF system is useful in decreasing run-off and increasing infiltration of rainfall on Vertic Inceptisols, there is a need to increase light use by soyabeans on BBF during the rainy season to increase its productivity. A watershed-based farming system needs to be adopted to capture significant amount of rain water lost as run-off and deep drainage. The stored water can be used for supplemental irrigation to increase productivity of soyabean-based systems leading to overall increases in resource-use efficiency, crop productivity and sustainability.

Breeding for disease resistance and yield in pearl millet

We describe a program at ICRISAT, India, for breeding pearl millet for disease-resistance and high grain yield. Large-scale, reliable techniques for screening in the field for downy mildew, ergot and smut have been developed and are routinely being used. Since downy mildew is economically important, all breeding material passes through the downy mildew-screening nursery and resistant varieties and hybrids have been bred. Synthetic varieties have been produced which are also resistant to smut and are agronomically good. Variability from African germplasm material, particularly for disease resistance, head volume, and seed size, has been exploited in crosses with Indian material. African parent-age occurs in nearly all of the advanced breeding products of the ICRISAT program. Recurrent selection has been used to produce open-pollinated varieties, one of which (WC-C75) is the first to be released in India where it already occupies a considerable hectarage. Conventional pedigree breeding has been used to produce synthetic parents, pollinators and seed parents. Several new seed parents have been released, and this broadens the genetic base of the hybrid crop which previously relied heavily on a single malesterile line.

Soybean–chickpea rotation on Vertic Inceptisols II. Long-term simulation of water balance and crop yields

A field study was conducted on a Vertic Inceptisol during 1995-1997 seasons at the ICRISAT Centre, Patancheru, India, to study the effect of two landforms (broadbed-and-furrow (BBF) and flat) and two soil depths (shallow and medium-deep) on crop yield and water balance of a soyabean-chickpea rotation. Using two seasons experimental data, a soyabean-chickpea sequencing model was evaluated and used to extrapolate the results over 22 years of historical weather records. The simulation results showed that in 70% of years total runoff for BBF was >35 mm (range 35-190 mm) compared with >60 mm (range 60-260 mm) for flat on the shallow soil. In contrast on the medium-deep soil it was >70 mm (range 70-280 mm) for BBF compared with >80 mm (range 80-320 mm) for the flat landform. The decrease in runoff on BBF resulted in a concomitant increase in deep drainage for both soils. In 70% of years, deep drainage was >60 mm (range 60-390 mm) for the shallow soil and ranged from 10 to 280 mm for the medium-deep soil. In 70% of years, the simulated soyabean yields were >2.2 t/ha (range 2.2-3.0 t/ha) and were not influenced by landform or soil depth. In the low rainfall years, yields were marginally higher for the BBF than for the flat landform, especially on the shallow soil. Simulated chickpea yields were higher for the medium-deep soil than for the shallow soil. In most years, marginally higher chickpea yields were simulated for the BBF than for the flat landform on both soil types. In 70% of years, the chickpea yields were >0.5 t/ha (range 0.5-1.5 t/ha) for the shallow soil, and >0.8 t/ha (range 0.8-1.96 t/ha) for the medium-deep soil. Total productivity of a soyabean-chickpea rotation was >3.0 t/ha (range 3.0-4.15 t/ha) for the shallow soil and >3.45 t/ha (range 3.45-4.7 t/ha) for the medium-deep soil in 70% of years. These results showed that in most years BBF increased rainfall infiltration into the soil and had marginal effect on yields of soyabeans and chickpeas. Crop yields on Vertic Inceptisols can be further increased and sustained by adopting appropriate rain water management practices for exploiting surface runoff and deep drainage water as supplemental irrigation to crops in a watershed setting.

Integrated watershed management for increasing productivity and water-use efficiency in semi-arid tropical India.

Poverty, food insecurity, and malnutrition are pervasive in the semi-arid tropics (SAT) of South Asia, including India. In rural areas, most of the poor make their livelihoods on the use of natural resources, which are degraded and inefficiently used. This is because of the inadequate traditional management practices of managing agriculture as well as the fact that resulting crop yields are much below the expected potential yields. ICRISAT in the early 1970s initiated research on watersheds for integrated use of land, water, and crop management technologies for increasing crop production through efficient use of natural resources, especially rainfall that is highly variable in the SAT and is the main cause of year-to-year variation in crop production in India. Improved watershed management on Vertisols more than doubled crop productivity, and rainfall-use efficiency increased from 35% to 70% when compared with traditional technology. After many years of implementing and evaluating these improved technologies in on-farm situations, many lessons were learned and they formed part of the integrated watershed management model currently being pursued by ICRISAT in community watersheds in rural settings. This watershed model is more holistic and puts rural communities and their collective actions at center stage for implementing improved watershed technologies with technical backstopping and convergence by consortium partners. We describe here the achievements made in enhancing crop productivity and rainfall-use efficiency by implementing improved technologies in on-farm community watersheds in India.