ICRISAT Center Research Articles

INTEGRATED NUTRIENT MANAGEMENT USING DEOILED JATROPHA CAKE FOR SUSTAINED AND ECONOMIC FOOD PRODUCTION

With growing environmental and energy concerns, Jatropha plantations are promoted in degraded/waste lands for the biodiesel production. Nutrient rich nonedible deoiled seed cake, a by-product of Jatropha left out after oil extraction was evaluated at the ICRISAT centre at Patancheru, India as an environment friendly source of nutrients for rainy season maize and soybean followed by postrainy chickpea in rainfed systems. Deoiled cake as partial (50%) or full replacement of recommended basal nitrogen (N) was found superior in terms of increased crop yield over the equivalent chemical fertilizers treatments. Highest yield and net returns under full replacement of basal N for maize, while under 50% basal N replacement in case of soybean and chickpea crops were recorded by 8 to 27% in grain yield and 10 to 28% in straw yield. Deoiled Jatropha cake as a full replacement of N dose in maize also recorded higher N uptake and use efficiency in maize than chemical N source treatment along with increased organic C and nutrient contents in post-harvest soil samples. This study revealed the benefits of Jatropha deoiled seed cake as a good source of plant nutrients and soil organic C in the semi-arid tropics in addition to enhanced C sequestration under Jatropha plantation on degraded waste lands.

Nitrogen response and water use efficiency of sweet sorghum cultivars

Sweet sorghum [Sorghum bicolor (L.) Moench] is a biofuel crop, which can be grown under tropical rainfed conditions without sacrificing food and fodder security. Three sweet sorghum cultivars (CSH 22 SS, NTJ 2 and ICSV 93046) with two row spacings (60 and 45cm) and six nitrogen levels (0, 30, 60, 90, 120, and 150kgha−1) were grown on Vertisols during three post rainy (November to April) seasons at the ICRISAT center farm in Patancheru, India. The results showed that the row spacings (60 or 45cm) had no influence on performance of the cultivars. Sweet sorghum hybrid CSH 22 SS produced the highest green stalk yield (45.4Mgha−1) and grain yield (2.33Mgha−1) compared to NTJ 2 (32.66Mgha−1 and 1.70Mgha−1) and ICSV 93046 (38.44Mgha−1 and 2.03Mgha−1). Net economic return from CSH 22 SS (US$ 681ha−1) was also significantly higher than that from NTJ 2 (US$ 415ha−1) and ICSV 93046 (US$ 539ha−1). All cultivars responded to applied N up to 150kgha−1; however beyond 90kgha−1N rate, the increase in yield was insignificant. Estimated N use efficiency (NUE) values indicated that 90kgNha−1 was an optimum N level for sweet sorghum crop. Simulated soil water balance components revealed that reduction in total transpiration due to water stress was 20 to 45% compared to the no-stress. In case of water use efficiency, CSH 22 SS showed the highest economic returns per unit volume of water input. Based on these results, it is concluded that sweet sorghum hybrid CSH 22 SS at 90kgNha−1 is the best remunerative combination for maximizing yield, economic returns and resource use efficiency.

Hydrological behavior of Alfisols and Vertisols in the semi-arid zone: Implications for soil and water management

Understanding of the hydrological behavior of soils is a prerequisite for developing appropriate soil and water management practices. Such information for Alfisols and Vertisols, the two major soils in the semi-arid tropics (SATs), is scanty especially from a long-term perspective. In this paper, we describe and discuss results from long-term (from 1976 to 2010) hydrological studies conducted on small agricultural watersheds on Vertisols and Alfisols at the ICRISAT Center, Patancheru, India. The hydrological behavior of soils are characterized in terms of runoff volume, peak runoff rate, number of runoff events, soil loss, sediment concentration and deep drainage loss under different rainfall, crop cover and soil moisture conditions to aid in developing effective soil and water management practices. We also provide details on the effects of annual and monthly rainfall on the hydrological behavior of these soils in different rainfall regions. The results show that Alfisols and Vertisols in the SATs have very contrasting hydrological behavior. Several findings emerging from our studies, are rather unexpected. For example, the sandy Alfisols with higher saturated hydrological conductivity generated higher runoff compared to the clayey Vertisols with extremely low saturated hydraulic conductivity. The undesirable early season runoff from Alfisols is higher than from Vertisols. The contribution of 1–2 big storms to annual runoff and soil loss was high on both soils. The contrasting hydrological behavior of these two soils is due to differences in soil characteristics such as crusting, sealing and low structural stability in Alfisols; and the presence of cracks during the early season and formation of micro-cracks during rainless periods in Vertisols. The results suggest that the information from the long-term hydrological studies is useful for determining appropriate soil and water management practices and strategies in different rainfall regions.

New early-maturing germplasm lines for utilization in chickpea improvement

Early-maturity helps chickpea to avoid terminal heat and drought and increases its adaptation especially in the sub-tropics. Breeding for early-maturing, high-yielding and broad-based cultivars requires diverse sources of early-maturity. Twenty-eight early-maturing chickpea germplasm lines representing wide geographical diversity were identified using core collection approach and evaluated with four control cultivars in five environments for 7 qualitative and 16 quantitative traits at ICRISAT Center, Patancheru, India. Significant genotypic variance was observed for days to flowering and maturity in all the environments indicating scope for selection. Genotypes × environment interactions were significant for days to flowering and maturity and eight other agronomic traits. ICC 16641, ICC 16644, ICC 11040, ICC 11180, and ICC 12424 were very early-maturing, similar to or earlier than control cultivars Harigantars and ICCV 2. The early-maturing accessions produced on average 22.8% more seed yield than the mean of four control cultivars in the test environments. ICC 14648, ICC 16641 and ICC 16644 had higher 100-seed weight than control cultivars, Annigeri and ICCV 2. Cluster analysis delineated three clusters, which differed significantly for all the traits. First cluster comprised three controls, ICCV 96029, Harigantars, ICCV 2 and two germplasm lines, ICC 16644 and ICC 16641, second cluster comprised 13 germplasm lines and control cultivar Annigeri, and third cluster comprised 13 germplasm lines. Maturity was main basis of delineation of the first cluster from others. Plot yield and its associated traits were the main basis for delineation of the second cluster from the others. Identification of these diverse early-maturing lines would be useful in breeding broad-based, early-maturing and high-yielding cultivars.

Variability for Drought Resistance Related Traits in the Mini Core Collection of Peanut

Peanut (Arachis hypogaea L.) productivity is low in the semiarid tropics mainly because of drought caused by low and erratic rainfall. Identification of genotypes that have a greater ability to use limited available water is important to enhance productivity of the crop. Water‐use efficiency (WUE) is correlated with specific leaf area (SLA) and soil plant analysis development (SPAD) chlorophyll meter reading (SCMR) and both have been suggested as surrogate traits for selecting for WUE in peanut. The present study was conducted to: (i) identify genotypes with high WUE using SLA or SCMR and (ii) evaluate relationship between and relative stability of SCMR and SLA in these genotypes. The 184 mini core entries, consisting of 37 fastigiata, 58 vulgaris, 85 hypogaea, two peruviana, and one each of aequitoriana and hirsuta and four control cultivars, M 13, Gangapuri, ICGS 44 and ICGS 76 were evaluated for SLA, SCMR, and 19 vegetative, reproductive, and quality traits in the 2001 rainy and 2001–2002 postrainy seasons at ICRISAT Center. Data were analyzed by REML analysis. Seasons were significant for all traits. Variances due to genotypes were significant for SCMR and SLA at 60 and 80 d after sowing (DAS) and other traits except pods per plant, yield per plant, haulm yield per plot, and protein and oil contents. The genotype × season interactions were significant for both SCMR and SLA at 80 DAS only and for all other quantitative traits except number of primary branches, and pod width. The SCMR values at different stages and seasons were more positively correlated with each other than the correlation of SLA values together. SCMR and SLA were negatively correlated. SCMR values were more strongly correlated with pod yield and other economic traits such as 100‐seed weight at both 60 and 80 DAS than SLA. On the basis of higher heritability and lower proportion of genotype × season interaction variance to phenotypic variance, SCMR appeared to be more stable than SLA. On the basis of SLA and SCMR values compared with the control cultivar, five vulgaris and 13 hypogaea accessions were selected. These accessions and control cultivars were grouped by scores of the first 15 principal components (PCs). The clustering by UPGMA method indicated that the selected accessions were diverse from the control cultivars and can be used in the peanut improvement programs to develop cultivars with a broad genetic base.

Sediment flow behaviour from small agricultural watersheds

Runoff, soil loss, sediment concentration, and particle size distribution of sediment eroded by runoff events were measured between 1976 and 2000 from 5 small agricultural watersheds on Vertisols at ICRISAT Center, Patancheru, India. The effects of storm size and land management system on total soil loss and size distribution of sediment during runoff are discussed. At the beginning of runoff events, the clay content of the eroded material was greater than that of the top soil but as the process of runoff continued, the clay content of the sediment tended to decrease. Generally smaller storms produced eroded material with higher clay content than did the bigger storms. Large differences in particle size distribution between the land management treatments were observed for small and medium runoff events, however, these differences were small during big runoff events. The particle size distributions of sediments eroded by big storms were comparable to the size distribution of cultivated top soil of the watersheds. The peak sediment concentration for most of the storms, generally preceded or occurred simultaneously with peak runoff rates. At about the peak runoff rate of most runoff events, the texture of the eroded soil was similar to the cultivated top soil of the watershed. Land management systems not only had significant effect on runoff and soil loss but also on the particle size distribution of eroded materials.

Sediment flow behaviour from small agricultural watersheds

Runoff, soil loss, sediment concentration, and particle size distribution of sediment eroded by runoff events were measured between 1976 and 2000 from 5 small agricultural watersheds on Vertisols at ICRISAT Center, Patancheru, India. The effects of storm size and land management system on total soil loss and size distribution of sediment during runoff are discussed. At the beginning of runoff events, the clay content of the eroded material was greater than that of the top soil but as the process of runoff continued, the clay content of the sediment tended to decrease. Generally smaller storms produced eroded material with higher clay content than did the bigger storms. Large differences in particle size distribution between the land management treatments were observed for small and medium runoff events, however, these differences were small during big runoff events. The particle size distributions of sediments eroded by big storms were comparable to the size distribution of cultivated top soil of the watersheds. The peak sediment concentration for most of the storms, generally preceded or occurred simultaneously with peak runoff rates. At about the peak runoff rate of most runoff events, the texture of the eroded soil was similar to the cultivated top soil of the watershed. Land management systems not only had significant effect on runoff and soil loss but also on the particle size distribution of eroded materials.

Predicting growth and development of pigeonpea: biomass accumulation and partitioning

Examining physiological relationships that quantify the processes of interception of radiation and biomass accumulation and partitioning provide one avenue for understanding limits to pigeonpea productivity. The radiation extinction coefficient ( k), radiation use efficiency (RUE), partitioning of biomass between leaf and stem before flowering, and the rate of linear increase in harvest index (HI) during pod-filling were determined for nine cultivars in water and nutrient non-limiting conditions at ICRISAT Centre, Patancheru, India. The nine cultivars comprised three each from the cultivar duration classes extra-short (100 days to maturity), short (115 days) and medium (170 days). Values of k and RUE were consistent across duration groups, with mean values of 0.53 and ca. 0.9 g MJ −1, respectively. RUE remained at its maximum value almost until maturity. Partitioning between leaf and stem prior to flowering was also consistent across groups, in the ratio of 1:1.03 to 1:1.14. The rate of linear increase in HI and final HI varied across groups, with lower rates of partitioning to grain and final HI in the later maturing groups. When adjusted for fallen leaf, the HI increase was ca. 0.08, 0.075 and 0.04 per day, and maximum HI was ca. 0.35, 0.32 and 0.19 for extra-short, short and medium-duration groups, respectively. The association of lower HI increase with indeterminate growth provides a convenient framework to simulate concurrent reproductive and vegetative growth during pod-filling.

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

In rainfed agriculture, climatic variability has profound effects on the performance of management systems in improvements of productivity and use of natural resources. A field study was conducted on a Vertic Inceptisol during 1995–1997 seasons at the ICRISAT Center, Patancheru, India, to study the effect of two landforms, i.e., broadbed-and-furrow (BBF) and flat, and two soil depths (shallow and medium-deep) on crop yield and water balance of a soybean–chickpea rotation. Using two seasons experimental data, a soybean–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 greater than 35 mm (range 35–190 mm) compared to greater than 60 mm (range 60–260 mm) for flat on the shallow soil. In contrast on the medium-deep soil it was greater than 70 mm (range 70–280 mm) for BBF compared to greater than 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 greater than 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 soybean yields were greater than 2200 kg ha −1 (range 2200–3000 kg ha −1) 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 greater than 500 kg ha −1 (range 500–1500 kg ha −1) for the shallow soil, and greater than 800 kg ha −1 (range 800–1960 kg ha −1) for the medium-deep soil. Total productivity of soybean–chickpea rotation was greater than 3000 kg ha −1 (range 3000–4150 kg ha −1) for the shallow soil and greater than 3450 kg ha −1 (range 3450–4700 kg ha −1) for the medium-deep soil in 70% of years. These results showed that in most years BBF, landform increased rainfall infiltration into the soil and had marginal effect on yields of soybean and chickpea. 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.

Leaf phosphorus and sorghum yield under rainfed cropping of a Vertisol

Little attention has been devoted to the calibration of plant P tests for sorghum, especially under rainfed cropping although information is needed for developing an efficient P management strategy for increasing crop productivity. A field experiment was conducted for three years (1987–1989) to study the response of sorghum to fertilizer P (0, 10, 20 and 40 kg P ha-1) on a Vertisol, low in extractable P, at the ICRISAT Center, Patancheru (near Hyderabad), India. One sorghum crop was grown each year during the rainy season (June–September). Leaf tissue samples consisting of newest, fully-developed leaf, were collected at 50% flowering stage of the crop, for establishing relationship between leaf P concentration and grain yield. During the three years,sorghum grain yield and leaf P concentration increased in response to P application up to 40 kg P ha-1 and the leaf P concentration was linearly related to grain yield (r2 varied from 0.724 to 0.993). The critical leaf P concentration at 90% of the maximum grain yield was found to be about 0.25% P. Phosphorus content in the grain was not significantly correlated to yield.

Identification of new sources of resistance to rust and late leaf spot in peanut∗

Abstract A total of 979 germplasm accessions was screened for resistance to rust and late leaf spot in preliminary field trials at ICRISAT Center, Patancheru, India during 1989–1990. Selected genotypes were further evaluated in separate advanced screening trials conducted with erect bunch [Spanish (var. vulgaris) and Valencia (var. fastigiata)], spreading bunch [Virginia bunch (var. hypogaea)], and runner [Virginia runner (var. hypogaea)] types during 1991–1993. Thirty‐eight genotypes (21 erect bunch, 5 spreading bunch, and 12 runner) were identified as resistant to rust, and seven (five erect bunch and two runner) to late leaf spot. Four genotypes (ICG Nos 6843, 10890,11567, and 12112) showed resistance to both rust and late leaf spot; ICG 10881 and ICG 11567 belong to the Spanish bunch group. Two genotypes [BPZ 691 and 259–2 (Red)] showed high level of resistance to late leaf spot, but were only moderately resistant to rust. The characteristic features of these sources of resistance are described, and t...

Nitrogen Requirements at Different Growth Stages of Short‐duration Pigeonpea (Cajanus cajan L. Millsp)1

AbstractThe response to N fertilization of a short‐duration pigeonpea genotype, ICPL 87, was studied in the field to assess the scope for genetically improving symbiotic N2 fixation by pigeonpea. The field study was undertaken during 1985, 1986 and 1987 growing seasons on Vertisol and Alfisol at ICRISAT Center (peninsular India), Inceptisol at Gwalior (central India) and Entisol at Hisar (northern India) in as non‐limiting environmental conditions as possible. Nitrogen fertilizer was applied to the soil at various growth stages to determine when N becomes most limiting. There was a significant response in grain yield to fertilizer N applied at flowering in Vertisol but not in Alfisol, Inceptisol or Entisol. This suggests that biological N2 fixation by short‐duration pigeonpea was not adequate to meet N requirements of the crop grown in Vertisol but that it was probably adequate in the other three soil types. These results are discussed in relation to the nodulation and acetylene reductase activity of pigeonpea and also N mineralization potential of different soils. It can be concluded that there is a need for genetic improvement of N2 fixing ability of short‐duration pigeonpea grown on heavy textured soils such as Vertisols.

Flowering of pigeonpea ( Cajanus cajan) in Kenya: Responses of early-maturing genotypes to location and date of sowing

The effects of temperature and daylength on durations from sowing to flowering ( f) were studied in six short-duration genotypes of pigeonpea ( Cajanus cajan) which had been classified as extra-early or early to mature at ICRISAT Center (17°N). Plants were grown in seven locations in Kenya covering a wide range of altitudes (50–2000 m) at latitudes ranging from 0° to 4°S. Experiments spanned two seasons, and were conducted in normal field conditions as well as under clear polythene enclosures constructed at six of the sites in order to provide warmer than ambient temperatures. All genotypes were also sown at monthly intervals as well as under an artificially extended daylength, both at Katumani (1°30′S). Mean pre-flowering values of temperature ( T) and photoperiod ( P) varied from 15.6° to 34.0°C and from 12.6 to 15.0 h, respectively. These photothermal conditions resulted in values of f between 53 and 118 d. Rates of progress from sowing to flowering ( 1 f ) were mostly unaffected by but were sometimes slightly responsive to photoperiod, whereas they responded consistently strongly to mean pre-flowering temperature ( T) below and above an optimum value close to 24°C. In the sub-optimal range the effects of T were positive and in the supra-optimal range they were negative, such that 1 f =a + bT and 1 f =a′ − b′T , respectively. The genotype-specific parameters a, b, a′ and b′ from these linear-rate models based on flowering responses in 27 environments were validated with independent data. Predicted values in f in 12 monthly sowings (range 62–99 d) did not differ significantly from those observed, i.e. for practical purposes within Kenya, the flowering responses of genotypes classified as extra-early or early to mature are insensitive to photoperiod. At more extreme latitudes (e.g. in India), and given the slight photoperiod sensitivity of some early-maturing genotypes, longer days can combine with supra-optimal temperatures to delay flowering.

Ergot resistance in sorghum in relation to flowering, inoculation technique and disease development

Ergot is an important disease of sorghum (Sorghum bicolor) in parts of Africa and Asia. Studies were conducted to determine the relationship between flowering biology and ergot infection, and to develop an artificial field‐screening technique to identify ergot resistance in sorghum. Spikelets resisted infection after anthesis, but each day's delay in anthesis after inoculation supported 8‐3% more ergot. The screening technique consisted of three components: trimming of panicles to remove pollinated spikelets before inoculation, a single inoculation of trimmed panicles, and panicle bagging for 7‐10 days. Inoculated panicles were evaluated by a qualitative visual rating method (on a 1‐5 scale) and a quantitative spikelet counting method. Selected accessions from the world collection of sorghum germplasm were screened at Karama Research Station, Rwanda, for two seasons and 12 ergot‐resistant lines were identified. These were also resistant at ICRISAT Centre, India.

Relationship between extracted phosphorus and sorghum yield in a Vertisol and an Alfisol under rainfed cropping

Little attention has been devoted to calibrating the soil tests for P in the field for crops grown under rainfed conditions in different soil types. Field experiments were conducted during the 1990 rainy season (June-September) at the ICRISAT Center, Patancheru (near Hyderabad), India on nearby Vertisol and Alfisol sites having a range in extractable P, for establishing relationships between extractable P and sorghum yield.

Response of sorghum to fertilizer phosphorus and its residual value in a Vertisol

The response of crops to added P in Vertisols is generally less predictable than in other soil types under similar agroclimatic conditions. Very few studies have considered the residual effects of P while studying responses to fresh P applications. Field experiments were conducted for three years to study the response of sorghum to fertilizer P applied at 0, 10, 20 and 40 kg P ha−1, and its residual value in a Vertisol, very low in extractable P (0.4 mg P kg−1 soil), at the ICRISAT Center, Patancheru (near Hyderbad), India. In order to compare the response to fresh and residual P directly in each season, a split-plot design was adopted. One crop of sorghum (cv CSH6) was grown each year during the rainy season (June-September). The phenology of the sorghum crop and its harvest index were greatly affected by P application. The days to 50% flowering and physiological maturity were significantly reduced by P application as well as by the residues of fertilizer P applied in the previous season. In the first year of the experiment, sorghum grain yield increased from 0.14 t (no P added) to 3.48 t ha−1 with P added at the rate of 40 kg P ha−1. Phosphorus applied in the previous year was 58% as effective as fresh P but P applied two years earlier was only 18% as effective as fresh P.

Variation in pathogenicity among single‐oospore isolates of Sclerospora graminicola, the causal organism of downy mildew in pearl millet*

Variation in pathogenicity (virulence and aggressiveness) of various single‐oospore isolates of Sclerospora graminicola, the causal organism of downy mildew in pearl millet, was studied. Oospore isolates were maintained as sporangial progenies on the susceptible pearl millet genotype 7042‐S through asexual generations. Twenty single‐oospore isolates obtained from samples of oospore inocula from three locations (the ICRISAT Centre, Coimbatore, and Hisar) in India, were tested for pathogenicity on 7042‐S. All the isolates were virulent on 7042‐S and they varied considerably, between and within locations, in infection efficiency (11–44% infection). The S. graminicola populations from the ICRISAT Centre and Hisar were significantly more aggressive than those from Coimbatore. Considerable variation was found among the 10 single‐oospore isolates from the ICRISAT Centre in infection efficiency and for latent period on a set of resistant and susceptible genotypes. Seven representative isolates, two each from the ICRISAT Centre (ICOS) and Coimbatore (CBOS), and three from Hisar (HSOS), exhibited variation in infection efficiency, sporangial production capacity, and oospore production rating on the susceptible genotypes 7042‐S and NHB 3. A pathogenic fitness index (PFI) was calculated for these isolates as the product of the reciprocal of the latent period × percentage infected seedlings × log10 sporangia per cm2 leaf area × oospore production rating. Aggressiveness of these isolates, measured as PFI, varied greatly. CBOS‐1 was the least aggressive with a PFI of 8·5 on NHB 3 and 69·6 on 7042‐S; the PFI of the other isolates ranged from 81·1 to 370·5. Downy mildew resistance in three of the five known resistant lines (700651, P7‐4 and 7042‐R) was consistently effective against all 10 ICOS isolates, indicating that the resistance of these three lines is likely to be more stable, at least at the ICRISAT location, than that of the other two resistant lines.

Components of Resistance to an Indian Source of Cercospora Arachidicola in Selected Peanut Lines1

Abstract Cercospora arachidicola Hori is one of the most important foliar pathogens worldwide that limits peanut production in farmers' fields. Earlier screening trials allowed us to identify lines with field resistance to early leafspot. In order to determine the components of resistance of these lines and other lines reported to be resistant elsewhere, 19 peanut genotypes (Arachis hypogaea L.) were evaluated by the detached leaf technique using an isolate of Cercospora arachidicola from the ICRISAT Center in India. Significant differences were observed among genotypes for all components of resistance included in the study. With a few exceptions, early leafspot- resistant genotypes (ICG nos. 8298, 6902, 6284, 1703, 10900, 7878, 9989 and 10920) exhibited longer incubation periods, reduced sporulation, smaller lesion diameters and lower infection frequencies than susceptible lines. Genotypes ICG 8298 and ICG 6902 were the most resistant, while ICG nos. 221, 7827 and 6340 were the most susceptible to early leafspot. A few lines had resistant reactions to some components but susceptibility to others.

Adaptation of Extra Short Duration Pigeonpea to Rainfed Semi-Arid Environments

SummaryThe adaptation of extra short duration (ESD) pigeonpea (Cajanus cajan) genotypes to rainfed environments was studied on Alfisols and Vertisols at the ICRISAT Center between 1987 and 1989. Despite a slightly shorter crop duration, the grain yield of ESD genotypes was twice as large on Alfisols as on Vertisols. On both soil types, the rate of growth and grain yield were better in crops sown on time than in those where sowing was delayed. The population levels necessary to maximize yield varied among genotypes on Alfisols, where the grain yield of several ESD genotypes compared favourably with that of ICPL 87, a standard short duration genotype. However, none of the ESD genotypes yielded more than ICPL 87 on the Vertisols.

Crop growth, water‐use efficiency and carbon isotope discrimination in groundnut (Arachis hypogaea L.) genotypes under end‐of season drought conditions*

SummaryTen groundnut genotypes were grown under adequately irrigated conditions or subjected to drought during the pod filling phase (83–113 days after sowing) in a medium deep Alfisol at the ICRISAT Centre during the 1986–1987 post‐rainy season. Crop growth was measured in both treatments, but transpiration (7) and water‐use efficiency (W) were quantified only in the drought treatment. Leaf samples from both treatments were assayed for discrimination against 13CO2 fixed in leaves (Δ) to examine the relationships between Δ, crop growth, and W under field conditions.The shoot dry matter accumulated during the period of drought (Y) ranged from 72–150 g m‐2 and was closely related to transpiration. This indicates scope for selection of traits and practices to increase T. Water‐use efficiencies ranged from 1.38–2.50 g kg‐1 and were inversely related to Δ in eight out of the 10 genotypes. For the other two genotypes, there was evidence that T was underestimated by field measurements. Water‐use efficiency and transpiration were not correlated suggesting that these two traits might be combined through breeding. Variation between genotypes was greatest for the partitioning of total dry matter to pods (73%), followed by water‐use efficiency (31%) and transpiration (29%). Crop growth rates were negatively related to Δ under irrigated conditions but not under drought.