Tropical India Research Articles

On-farm Experiments as a Diagnostic Method: Constraints to Nitrogen Fertilizer Use on Sorghum in Semi-arid Tropical India

SUMMARYOn-farm diagnostic experiments were used to study constraints to nitrogen fertilizer use, define recommendation domains, and test fertilizer management techniques for two sorghum cropping systems in semi-arid tropical India. In the post-rainy season sorghum cropping system, nitrogen fertilizer use remains negligible because crop response is poor when sorghum is planted after the end of the monsoon, as is traditional. An earlier planting date would introduce high risks. In the dependable rainfall region, nitrogen fertilizer use on hybrid sorghum could be enhanced by tailoring recommendations to broad farmer-designated soil groups, and by educational programmes on the use of complex fertilizers. Additional research on fertilizer efficiencies on shallow Vertisols is needed. Diagnostic experiments proved a useful, relatively rapid and low cost method of research when complemented by farm management and on-station research data.

A New Species of Portulaca from Kenya and Somalia

Summary. Portulaca decorticans sp. nov. is described as new. It is restricted to granitic outcrops in northern Kenya and southern Somalia. Portulaca can be divided very conveniently into species with non-articulated stems, usually alternate leaves and strictly axillary hairs and scales and those with articulated stems, strictly opposite leaves and with either a complete nodal whorl of hairs and scales (the stipules of many authors) or with no appendages. The latter group is, except for one aggressive weed, restricted to Australia and Africa plus those areas of Asia with well-known African affinities: tropical Arabia, southern India and Sri Lanka. It includes about 20 rather well-defined species that will be the subject of another account (Gilbert & West in prep.). The former group, found world-wide but with a major centre of diversity in the New World, poses much more intractable problems, even on a local, strictly African, scale. Both Peter (1932, 1938) and von Poellnitz (1934, 1940) worked extensively on the group and described a number of new species from Africa, mostly based on Tanzanian collections. Examination of all their types in Berlin, most of which survived the Second World War, and available herbarium material strongly suggests that a significant proportion of their taxa may well not merit recognition. It is also clear that there are further groups of specimens that might represent undescribed species. The variation is most complex in the area from central Kenya to central Tanzania and it is clear that the situation there can only be satisfactorily clarified by examining the genus in the field-herbarium material gives very little feel for the group because of the difficulty of dealing with often fragmentary specimens with very poorly preserved flowers. However there is one group of specimens from northern Kenya that stand out as representing a species quite distinct from anything described to date. As it is known from three separate localities on or very near to the border with Ethiopia, it must surely also occur in southern Ethiopia and should thus be mentioned in the account of the family for the Flora of Ethiopia. It is therefore formally described below.

Water-soluble, exchangeable and nonexchangeable potassium in six soil series from tropical India

SUMMARYSix soil series differed in water-soluble, exchangeable and nonexchangeable K. Significant positive relationships were observed between exchangeable K and water-soluble K. A highly significant positive relationship was found between the K saturation of the cation exchange complex and water-soluble K in the individual soil series, and when the six series were pooled; K saturation, therefore, may predict water-soluble K in a range of tropical soils. Potassium desorbed in 35 min by electroultrafiltration (EUF) may serve as a measure of exchangeable K in predominantly kaolinitic tropical soils. In soils with appreciable amounts of mica, longer K extraction by EUF (up to 70 min) may indicate the reserves of nonexchangeable K.

Influence of Osmotic Adjustment on the Growth, Stomatal Conductance and Light Interception of Contrasting Sorghum Lines in a Harsh Environment

Two drought resistant lines of sorghum, IS 13441 and IS 1347, with a high capacity for osmotic adjustment and two susceptible lines, IS 12739 and IS 12744, were subjected to drought in the field during a summer season in the semi-arid tropics in India. During this season there is little rain, air temperatures reach 42°C, and pan evaporation rates may reach 20 mm d-1 providing a harsh environment for crop growth. Most of the osmotic adjustment occurred within 3 weeks after withholding water and at high predawn leaf water potentials, i.e. at values above - 1.0 MPa. As a result, resistant lines were able to maintain a positive turgor to lower leaf water potentials (- 2.8 MPa) than susceptible lines (- 2.0 MPa). Nevertheless, dry matter production was negligible in both resistant and susceptible lines when predawn leaf water potentials fell to - 0.55 MPa. Furthermore, throughout the drought period the leaf area of all water-stressed plants was similar when expressed relative to the control regardless of the level of osmotic adjustment. Resistant lines had similar stomatal response to leaf water potential as susceptible lines. Large changes occurred in stomatal conductance and leaf rolling soon after withholding water while there was considerable osmotic adjustment in the leaves. Leaf rolling coincided with a reduction in the ability of the plant to utilise radiation. Therefore, even if osmotic adjustment had delayed leaf rolling, the gain in productivity would be small. On the basis of these turgor related processes it can be concluded that there would be little advantage in selecting for plants with a higher capacity for osmotic adjustment in this harsh environment.

Leaf emergence on main stem in the peanut cultivars-observations under the irrigated field conditions in semi-arid tropical India.

Leaf emergence on main stem in the peanut cultivars-observations under the irrigated field conditions in semi-arid tropical India.

A modified contour bunding system for Alfisols of the semi-arid tropics

Contour bunding is the most widely practised soil conservation measure on Alfisols of the semiarid tropics in India. The conventional contour bund system allows water to stagnate for long periods in extensive areas along the bunds that affects crop yields in these areas. Crop yields from sorghum/pigeon pea intercrop and pearl millet/pigeon pea intercrop at different distances from the bunds were measured to demonstrate the effects of bunding. The effects of eroded sediment deposition on the infiltration behavior of the zone near the bunds are also discussed. A modified contour bunding system with gated outlets is described. Contour bunds with gated outlets were found to ensure adequate control of runoff and soil loss. Crops grown in the fields bunded by gated outlets yielded better than those grown in fields surrounded by conventional bunds. The water balance of the ponded areas near the bunds is presented for both the modified and conventional contour bunding systems.

Acute renal failure due to viperine snake bite as seen in tropical western India.

A wide spectrum of clinicopathological changes have been described in 50 cases of ARF following viperine snake bite studied prospectively over a 15-year period. Disseminated intravascular coagulation (DIC) was seen in 24/50 cases (Russel's viper bite in 62% and Ecchis carinatus bite in 42% of subjects). Histological examination of renal tissue obtained 1.5 days to 8 weeks after the bite revealed proliferative glomerular changes in 17 cases. These were characterized by ballooning of the capillaries, thickening and splitting of glomerular basement membrane (GMB), fibrin thrombi in the capillaries, and mesangial cell proliferation most prominently seen in Ecchis carinatus bites resulting in ARF.

Man and Forests: A Case-study from the Dry Tropics of India

The present study analyses the energy-budget of ‘village ecosystems’ in a dry tropical environment. These systems depend to a great extent on the surrounding natural forest/savanna ecosystems. Accordingly the objectives of the study were to quantify (i) the energy efficiency of rain-fed agriculture at the ecosystem level, and (ii) the indirect impact of agricultural activity on the surrounding forest/savanna ecosystems.Agronomic output from farming is not sufficient to meet the food-energy requirements of the villagers, hence 27.0 to 51.0% of the requirement is met from outside markets. Operation of the agro-ecosystems involved requires a considerable amount of subsidy from the surrounding forest/savanna ecosystems in terms of fodder and fuel-wood. About 81 to 100% of the fuel needs, and 80–87% of the fodder needs, are met from the natural forest/savanna ecosystems. Thus, for each unit of energy obtained in agronomic yield (including milk), 3.1 units of energy are expended from the surrounding natural ecosystems in the form of fodder and fuel-wood.The erratic and ill-distributed nature of monsoon rains results in moisture deficit which affects the crop production in dry-land farming, causing partial or total failure of the crops. For achieving increased and stable agronomic production under rain-fed conditions, improved dry-land farming techniques have to be applied. Some of these techniques are: (1) introduction of crops and varieties that would be capable of maturing in a period of 90–100 days, and adequate use of appropriate fertilizers; (2) planned rain-water management including storage of surface runoff; and (3) practices of intercropping with crops of longer duration than those currently grown, having slow growth-rates in the early part of their life-cycles.

Institutional credit for Green Revolution areas under semi-arid tropics in India

Institutional credit for Green Revolution areas under semi-arid tropics in India

Effect on yield and juice quality of sugarcane following rice

Sugarcane is usually grown after paddy in tropical and subtropical India; this rotation is adopted when sugarcane is planted in October (autumn planting). Soil puddling is required for paddy, but puddling disturbs the soil structure and impedes development of roots beyond the puddled layer. Adverse effects on growth and yield of sugarcane are therefore expected, but contrary to such expectations, sustained or increased yields of cane after paddy have been observed (Alvarez & Snyder, 1984; Anon. 1984; Snyder el al. 1986). It appears that certain other soil factors overcome the harmful effects of adverse soil physical conditions. Therefore, the present study was undertaken to investigate such factors.

Energy input-output studies of some crop sequences based on short-duration sugarcane in relation to the conventional sugarcane system in tropical India

In India, sugar-rich short-duration (8 months) sugarcane varieties are being evolved for crop intensification through multiple cropping systems, with the objective of increasing sugar and agricultural output. Such systems require greater quantities of inputs and thus are energy intensive. A favourable energy balance is essential for sustaining productivity. In this study, energy use through various inputs to cropping systems based on short-duration sugarcane has been assessed and energy output-input ratios worked out. Multiple cropping systems based on short-duration sugarcane (with three to four crops per cropping cycle of 2 years) required about 40% more energy input than the conventional system of two sugarcane crops (one plant + one ratoon). In particular, energy inputs through fertilizers and labour were higher. Systems based on short-duration sugarcane gave a 14–27% higher energy output than the conventional system. Energy output-input ratios were slightly less in these systems than in the conventional one.

Market Impacts of Technological Change for Sorghum in Indian Near‐Subsistence Agriculture

AbstractEvaluating market impacts of technological change for near‐subsistence crops like sorghum in semiarid tropical India is complicated because of diversified agricuiture, geographically isolated markets, and therefore feedbacks through prices, and producer‐demander income links for such products. Dynamic simulations with a multicommodity market model suggest that increased sorghum productivity would have spillover effects on other markets, increase the welfare of sorghum consumers, and probably lower the sorghum price. Contrary to speculations of some experts, the output gain probably would be greater than the pure productivity effect despite the price decline because of induced input allocations favoring sorghum production.

Patterns of diel oxygen change in ponds of tropical India

Patterns of diel oxygen change in ponds of tropical India

Critical limits of deficiency and toxicity of zinc in paddy in a typic Ustipsamment

Abstract A pot culture experiment was conducted to establish the critical limits of deficiency and toxicity of Zn in a Typic Ustipsamment from tropical India. Critical limits of Zn deficiency and toxicity were 0.39, and 12 μg/g with DTPA‐TEA‐CaCl2, 2.2 and 26 μg/g with EDTA‐(NH4)2Co3 and 0.78 and 12 μg/g with HC1 (0.05 N), respectively. Critical concentrations in the rice plants associated with deficiency and toxicity were 16 and 190 μg/g.

Vertical Motions within the Indian Tropical Middle Atmosphere

Abstract Computations of vertical motions in the middle atmosphere over the Indian tropical region have been made based on the thermodynamic equation with the geostrophic approximation. The authors have used the once weekly rocketsonde temperature and wind data for the tropical station Thumba India, (8°32′N, 76°52′E) for the four summers (1972, 1973, 1975 and 1976) and two winters (1971 and 1972) which are also years of varying monsoon activity. In the tropical middle atmosphere, downward motion (subsidence) is the dominant feature when the motion field is considered in a longer time scale. The trend of fluctuations in vertical motion suggests wave structures in the tropical middle atmosphere. The magnitude of the extreme values of the vertical motion in the stratosphere over the high latitudes is larger, by a factor of 2 or more, than those obtained over the low latitudes (tropics). Whereas the magnitude of the vertical motion in high latitudes is associated with stratospheric warmings during winter, the...

Optimum design of small reservoirs (tanks)

Small reservoirs, called tanks, are a part of traditional water harvesting methods in the semiarid tropics of India and many other countries. Though considerable investment is being planned to construct more of them, no investigation has taken place to discover the most efficient design of these tanks. This paper proposes a nonlinear optimization model to design these tanks. It is, in a sense, ‘appropriate technology’ because a traditional approach is combined with newer techniques to improve irrigation systems without capital intensive or high technology construction methods.

Major quasi-periodic fluctuations in the drought indices

Modified Palmer drought indices for six district areas, two each from arid, semi-arid and dry subhumid climatic regions of tropical India, have been examined for the fluctuations of drought indices series covering a period of 70 years (1901–1970). Power spectrum analysis of the drought indices series revealed statistically significant quasi-periodicities of 3.3, 6.6, 10 and 20 years with regional preferences. The first two of these periods are close to the two modal peaks of the Southern Oscillation suggesting that the oscillations of the drought indices may be connected to the large-scale atmospheric pressure in the Indo-Pacific region. The other two periods 10 and 20 years are close to the 11-year sunspot cycle and the 22-year double sunspot cycle. The influences of solar activity and the Southern Oscillation on the Indian climate seem to be causal features for introducing these quasi-periodic cycles in drought indices fluctuations.

On some Psychodidae (Diptera: Nematocera) from Senegambia

AbstractA small collection of Psychodidae from Senegambia, West Africa, contained the following species: the cosmopolitans Tinearia alternata (Say), Psychoda parthenogenetica (Tonnoir), the tropicopolitan Clogmia albipunctata (Williston), Brunettia albonotata (Brunetti), common in tropical Africa and India, and a new species. Setomima senegambica n.sp., is described and compared with the already known species of the genus.

Periodicity of Cambium and the Formation of Xylem and Phloem in Mimusops elengi L., an Evergreen Member of Tropical India

The periodicity of cambium and the formation of xylem and phloem have been studied in Mimusops elengi L., for three consecutive calendar years (1974 to 1976). It has been found that following the thinning of the crown in April, new leaves emerge in May and this is followed by the initiation of cambial activity in June, after a lapse of 4 weeks from the time of leaf emergence. The cambial activity continues up to mid-November. Xylem formation starts from July and precedes phloem formation which occurs from August to November.

Chemical equilibrium and E value of Zn (ZnE) in inceptisols and entisols of tropical india

The chemical equilibrium and E value for Zn was calculated in 9 soils of Haryana (India) which represented mainly entisol and inceptisols. The rate of isotopic exchange between65Zn and native soil Zn was quite rapid and radioactivity reduced to about 0.2 per cent of initial activity after 3 days but total Zn concentration in soil solution did not decrease. In 5 out of 9 soils equilibrium was established in 2 to 3 days. In typic ustochrepts having high clay content (3,4) equilibrium was attained in two days. In typic udipsamments (2), typic camborthids (8) and aquic vertic ustichrepts (9) it took 3 days to set equilibrium. Typic ustochrepts (5) took 5 days for equilibrium whereas typic ustipssaments (6) and typic camborthids of high O.C. did not attain equilibrium even in 7 days. This indicated that the chemistry and availability of Zn in soil would depend on soil types.