The Effects of Plant Population Density on the Growth and Chemical Composition of Lablab purpureus Grown for Fodder Production in a Semi-Arid Region

Lablab purpureus was grown in two 6-month field experiments in the Savannah region of Africa, with high rainfall and hot temperatures in the first 2 months, followed by low rainfall and cool temperatures until harvesting in January. The experiments evaluated the effects of plant population density (PPD), using rows at 70-, 110- and 150-cm intervals, on the yield and nutritive value of the crop, and the effect of an interim harvest on response to PPD. Lablab yield ha⁻¹ was increased to a greater extent by an increase in PPD from 110 to 70 cm interrow spacing than by an increase from 150 to 110 cm, and yield plant⁻¹ decreased as PPD increased to a greater extent for double-harvested than for single-harvested plants. This suggested that high PPD in the early stages of growth is important to promote high crop yields in this environment, probably because it mitigates drought effects in autumn. The effects of PPD on herbage composition were small and suggested that plant maturity had not been greatly affected by density. It is concluded that the maintenance of plant cover in the early stages of growth is important for high yields in the Savannah region, which can be achieved by an interrow spacing of no more than 70 cm and avoidance of an interim harvest.     

Shoot and Root Production and Nitrogen Uptake in Barley, with and without Nitrogen Fertilization

Two barley crops, one fertilized with 120 kg N ha⁻¹ (B120) and the other without nitrogen fertilization (BO), were cultivated for the second year on the same plot. In 1981 the growth and nitrogen content of the whole plant, above- and below-ground parts were measured by sampling every second week. Production was calculated as the difference between annual maximum and minimum amounts of biomass found above- and below-ground. Nitrogen uptake was estimated as the sum of the peak amounts of nitrogen present in the roots and shoots. The amount and concentration of nitrogen in partly decomposed plant debris in the soil was estimated simultaneously with the biomass.
Total net production in B120 was 1004 g m⁻² of which the roots constituted 16%. The unfertilized barley produced 558 g m⁻² of which 23% were produced below-ground. The maximum amount of living roots found in B120 was 160 g ash-free dry mass m⁻² and 128 g m⁻² in BO.
In the fertilized treatment 15 g N m⁻² (21% in roots) was taken up by the plant, compared to 5.8 g N m⁻² (28% in roots) in the unfertilized crop.     

Growth dynamics of winter wheat in the field with daily fertilization and irrigation

In a field experiment with fertilized and irrigated winter wheat the above-ground crop was sampled once a week. Phenological development, plant density and canopy height were recorded and the green surface areas of leaves, stems and ears were measured. Soil mineral nitrogen was sampled and the field climate monitored. There were four treatments. The daily irrigated/fertilized (IF) and daily irrigated (I) treatments were both irrigated by a drip-tube system. Liquid fertilizer was applied to IF following a logistic function according to calculated plant uptake. A total of 200 kg N ha⁻¹ was applied. Treatment I, control (C) and drought (D) were all fertilized once in spring with 200 kg N ha⁻¹. In treatment D transparent screens were used to divert rainwater. Dry matter production ranged between 1400 in D and 2352 g m⁻² in IF. The corresponding amount of nitrogen uptake ranged between 15.8 and 24.6 g m⁻². After harvest, soil mineral nitrogen was lowest in IF.
An increase in the availability of nitrogen and water enhanced total biomass production as well as grain yield and leaf area. The daily supply of nitrogen according to crop demand delayed nitrogen uptake and increased total uptake. The results suggest that when the nitrogen is supplied in accordance with crop demand, the efficiency with which the applied fertilizer is utilized increases and the risk for nitrogen leaching decreases.     

Cover Crops for Saline Soils

A 3-year study was conducted in the Central Valley of California to evaluate 125 prospective winter-growing cover crops for growth and nitrogen productivity in saline soils. Soil saturation paste electrical conductivities (ECes) in the surface 15 cm averaged 7 dS  m⁻¹ at fall planting and 5.3 dS m⁻¹ at spring harvest dates of each experiment. Species evaluated varied substantially in plant height. In general, the tallest plants were the Brassica species, which consistently grew to over 1.4 m. Annual grasses (barley, rye, triticale and wheat) averaged about 1.0–1.3 m in each year. Of the legume species screened, heights were greatest for Hedysarum coronarium , Trifolium alexandrium , Vicia spp., and Medicago polymorpha and truncatula , averaging 59, 47, 39, 38 and 37 cm, respectively, over all experiments. About one third of the species screened produced crop cover in excess of 90 % in each year. Groups of plants with consistently high crop cover percentages included various species/accessions of Brassica , Hedysarum , annual grasses, cool-season annual medics, Medicago polymorpha and Medicago truncatula , and two annual clovers, Trifolium alexandrium cv 'Multicut' and rose clover, Trifolium hirtum cv 'Hykon.' Total above-ground plant dry weights were highest for Brassica spp., which produced twice as much biomass as the annual grass species, and roughly four times as much dry matter as any of the legume species. Hedysarum , Lana and Namoi woolypod vetch, purple vetch, berseem clover, and several of the annual medic species consistently had the highest biomass among the legumes.     

Optimum Seed Rate and Nitrogen Fertilizer Requirement of Rice Under Semi-deepwater Ecosystem

The effect of varying seed rates (100–1000 seeds m⁻²) and nitrogen fertilizer (0–60 kg N ha_-1) applied either in a single basal dose or in splits was investigated on a tall elongating, photosensitive rice variety, Nalini, under semi-deepwater conditions (0–100cm) during 1993 and 1994 at Cuttack, India. Seedling emergence was higher in 1993 (53.9 %) than in 1994 (44.1 %) and it increased proportionately with increasing seed rate, Increase in the number of tillers and panicles m⁻² at higher seed rates was associated with a corresponding decrease in panicle weight. Regression analysis indicated a decrease of 0.91–1.28g in panicle weight for an increase of 100 panicles m⁻². The grain yield of rice was significantly higher at 400 seeds m⁻² in 1993 and at 600 seeds m⁻² in 1994 than at low seed rates but further increase in seed rate did not increase the yield. Application of N fertilizer increased the panicle number and thereby grain yield significantly. The effect of basal and split applied N at active or maximum tillering stages as well as between 30 and 60 kg N ha⁻¹ was not significant on the grain yield. The results suggest that a basal dose of 30kg N ha⁻¹ and seeding density of 400–600 seeds m⁻², resulting in 40–50 % seedling emergence and 150–200 panicles m⁻², each with 2.0–2.5 g weight, may be adequate for optimum productivity of rice under semideepwater conditions.     

Soybean Yield and Yield Components in Two Planting Patterns

Soybean [Glycine max (L.) Merr.] plant density for maximum yield in Japan is usually from 16 to 25 plants m⁻². The objective of this study was to compare yield and yield components, especially node number between square- and zigzag- (an equilateral triangle-planting pattern or plants in the row offset from each other) planting patterns within a range of plant populations (16, 20 and 25 plants m⁻²).
Field experiments with cultivar Enrei (Maturity Group VII) were conducted in the field at Niigata University on a loamy sand soil in 1991, 1992 and 1993.
Yield increased as density decreased in 1991 and as density increased in 1992 and 1993. This result seemed to be due to adverse weather conditions during seed filling in 1991. Yield tended to be higher in zigzag- than in square-planting patterns except at 20 plants m⁻². Seed number m⁻² due to increased yield was highly correlated with branch node number. The yield increase was caused by an increase in total node number, especially branch node number m⁻² (about 60 % contribution at 16 plants m⁻² and about 40 % contribution at 25 plants m⁻²).     

Effect of Foliar Applications of Glycinebetaine on Stress Tolerance, Growth, and Yield of Spring Cereals and Summer Turnip Rape in Finland

Crop losses caused by environmental stresses might be reduced by applying osmoprotectans to crop canopies. Glycinebetaine is endogenously accumulated by some halophytes under stress conditions and represents such a compound. Glycinebetaine was applied exogenously to barley ( Hordeum vulgare L.), oat ( Avena sativa L.), spring wheat ( Triticum aestwum L.), and summer turnip rape ( Brassica rapa ssp. oleifera DC.) canopies and its optimal concentration was monitored in the greenhouse. In field experiments the response of crop plants to betaine applications was assessed by measuring accumulation of above ground biomass, leaf area index (LAI), leaf chlorophyll, and yield. The optimum betaine concentration producing advantageous effects on growth and crop physiology in turnip rape was close to 0.1 M and for wheat 0.3 M. Such concentrations promoted accumulation of betaine similar to that of halophytes under stress conditions [ca. 200 μmol (g DM)⁻¹]. In the 1993 field experiment peak LAIs were recorded in irrigated wheat and barley treated with 17.5 kg ha⁻¹ betaine applied at 300 1 ha⁻¹. Green leaf area was slightly more persistent in wheat treated twice with 1 kg ha⁻¹ betaine applied at 200 1 ha⁻¹ in 1994, although it was not associated with increased grain yield. Our results indicated that betaine has no actual potential in Finland for the principal grain crops but further studies are needed in stress prone environments to assess the potential of betaine treatments for preventing crop failures.     

Effect of 1-Naphthaleneacetic Acid Concentrations and the Number of its Applications on the Yield Components, Yield and Fibre Properties of Egyptian Cotton (Gossypium barbadense L.)

Field experiments were performed in two successive seasons at the Experimental Station, Faculty of Agriculture, Cairo University, Giza, Egypt, on the Egyptian cotton cultivar Giza 75 ( Gossypium barbadense L.). Cotton plants were sprayed with the growth regulator 1-naphthaleneace acid (NAA) once (at 90 days), or twice (at 90 and 105 days) or thrice (90, 105 and 120 days) after sowing, during the square initiation and boiling stage at the concentrations of 5, 10, 15, 20 or 25 p.p.m. The volume of solution was the same for all treatments. 9601 ha⁻¹. The control plants were sprayed with water only. The effect of the previous treatments on yield components, cotton yield and fibre properties was studied.
The application of NAA increased the number of opened bolls plant⁻¹, boll weight, seed index, seed cotton yield plant⁻¹ and seed cotton and lint yields ha⁻¹. The most significant effects were obtained with the 15 and 20 p.p.m. concentrations. Lint percentage, fibre length parameters and micronaire value were not significantly affected by NAA. Flat bundle strength was significantly affected by NAA but with no definite trend. The application of NAA twice or thrice tended to give the best results on yield components and cotton yield compared with one application. The results of this study suggested that 20 p.p.m. of NAA gave the best figures when applied twice on the Egyptian cotton plants.     

Effects of Salinity and Mixed Ammonium and Nitrate Nutrition on the Growth and Nitrogen Utilization of Barley

The absorption and utilization of nitrogen (N) by plants are affected by salinity and the form of N in the root medium. A hydroponic study was conducted under controlled conditions to investigate growth and N uptake by barley ( Hordeum vulgare L.) supplied with five different NH₄⁺-N/NO₃⁻-N ratios at electrical conductivity of 0 and 8 dS m⁻¹. The five NH₄⁺-N/NO₃-N ratios were 0/100, 25/75, 50/50, 75/25 and 100/0, each giving a total N supply of 100 mg N l⁻¹ in the root medium. A mixed N supply of NH₄⁺ and NO₃⁻ resulted in greater accumulation of N in plants than either NO₃⁻ or NH₄⁺ as the sole N source. Plants produced a significantly higher dry matter yield when grown with mixed N nutrition than with NH₄⁺ or NO₃⁻ alone. Total dry matter production and root and shoot N contents decreased with increasing salinity in the root medium. The interaction between salinity and N nutrition was found to be significant for all the variables. A significant positive correlation (r=0.97) was found between nitrogen level in the plant shoot and its dry matter yield.     

Interactive Effects of Salinity and Biological Nitrogen Fixation on Chickpea (Cicer arietinum L.) Growth

The effect of salinity on the nodulation, N-fixation and plant growth of selected chickpea- Rhizobium symbionts was studied- Eighteen chickpea rhizobial strains were evaluated for their growth in a broth culture at salinity levels of 0 to 20 dS m⁻¹ of NaCl + Na₂SO₄. Variability in response was high. Salinity generally reduced the lag phase and/or slowed the log phase of multiplication of Rhizobium. Nine chickpea genotypes were also evaluated for salt tolerance during germination and early seedling growth in Petri dishes at five salinity levels (0–32 dS m⁻¹). Chickpea genotypes ILC-205 and ILC-1919 were the most salt-tolerant genotypes. The selected rhizobial strains and chickpea cultivars were combined in a pot experiment aimed at investigating the interactive effect of salinity (3, 6 and 9 dS m⁻¹) and N source (symbiosis vs. inorganic N) on plant growth. Symbiotic plants were more sensitive to salinity than plants fed mineral N. Significant reductions in nodule dry weight (59.8 %) and N fixation (63.5 %) were evident even at the lowest salinity level of 3 dS m-¹. Although nodules were observed in inoculated plants grown at 6 dS m-¹, N-fixation was completely inhibited. The findings indicate that symbiosis is more salt-sensitive than both Rhizobium and the host plant, probably due to a breakdown in one of the processes involved in symbiotic-N fixation. Improvement of salinity tolerance in field grown chickpea may be achieved by application of sufficient amounts of mineral nitrogen.     

The Effect of Planting Date and Plant Density on Potassium and Magnesium Uptake and Harvest by Brussels Sprouts

The effects of planting date and plant density on potassium (K) and magnesium (Mg) uptake and harvest by Brussels sprouts ( Brassica oleracea var. gemmifera ) were studied in field experiments. Crop potassium concentration generally decreased towards harvest, but the pattern in potassium concentration during crop growth differed between planting dates. Plant density in the range of 2.7–4.4 plants m⁻² had no effect on crop potassium concentration. The amount of potassium in the crop at harvest decreased with a delay in planting, but was not influenced by plant density. Mainly depending on the planting date, around 100–200 kg potassium ha⁻¹, or approximately 40–50 % of the potassium in the crop at harvest, is removed from the field with the product. Averaged over treatments and years, potassium concentration in the (fresh) product was 5.2 kg ton⁻¹. The amount of magnesium in the crop at harvest decreased with a delay in planting. Depending on the planting date, uptake at harvest was 10–17 kg magnesium ha⁻¹. Plant density had no effect on this amount. On average per ton (fresh) product, 0.20 kg of magnesium was removed from the field.     

Yield and Resource Use Optimization in Late Transplanted Mint (Mentha arvensis) under Subtropical Conditions

A field experiment was conducted during 1994 and 1995 at Lucknow (26.5°N, 80.5°E, 120 m above mean sea level) to optimize planting density and fertilizer-N application for high essential oil yield of late transplanted mint ( Mentha arvensis ). The treatments studied were 2.5, 2.0 and 1.66 × 10⁵ mint seedlings ha⁻¹ and 0, 80, 160 and 240 kg N ha⁻¹. Under 3 months delayed planting conditions using 2-month-old seedlings, the high planting density of 2.5 × 10⁵ plants ha⁻¹combined with 160 kg N ha⁻¹ gave significantly higher herb and essential oil yields compared with those of lower planting densities (2 and 1.66 × 10⁵ plants ha⁻¹) and all other rates of N application. It is demonstrated that a transplanted mini crop, yielding essential oil at a level of 164 kg ha⁻¹, is feasible after the harvest of rabi cereal, oil seed or legume crops in the north Indian plains.     

Growth and Yield Response of Lentil Cultivars to Phosphorus, Zinc and Biofertilizers

A field experiment was conducted to study the growth and yield responses of lentil cultivars to phosphorus, zinc and biofertilizer application on a sandy loam soil during the winter seasons of 1989–90 and 1990–91 at the farm of Division of Agronomy, Indian Agricultural Research Institute, New Delhi, India. The two lentil cultivars used in the study were Microsperma (JL 1) and Macrosperma (Lens 4076) and the biofertilizers were Rhizobium and VAM fungi. Results showed that higher values of LAI, root nodulation, yield attributes (number of pods plant⁻¹, number of grains pod⁻¹ and grain yield plant⁻¹), grain yield and harvest index were obtained from JL 1 whereas plant height and 1000 grain weight were higher in Lens 4076. Application of 17.2 kg Pha⁻¹ as single superphosphate (SSP) along with 5 kg Znha⁻¹ as zinc sulphate resulted in marked improvement in growth and yield attributes, grain yield and harvest index when compared with the 17.2 kg P as rock phosphate (with and without Zn) and the control treatments. Combined inoculation of Rhizobium and VAM fungi resulted in improved growth and yield attributes, grain yield and harvest index when compared with inoculation of either of the inocula at a time.     

Intra-specific Variation for Salt Tolerance in Linseed (Linum usitatissimum L.)

Thirty-six accessions of linseed ( Linum usitatissimum L.) were screened for salt tolerance at the seedling stage after 2 weeks growth in solution culture salinized with 150mol m⁻³ NaCL Considerable variation in salt tolerance was observed in this set of germplasm. Two salt-tolerant accessions, T-5(69-S9)B and LS-2 and two salt-sensitive accessions P-70 and Aver-Rer-Seic, selected at the seedling stage, were grown to maturity in sand culture salinized with 0 (control), 70, 140, and 210 mol m⁻³ NaCl. Both the salt-tolerant accessions exceeded the two salt-sensitive accessions in biomass production, seed yield, and yield components, but the accessions did not differ significantly in seed oil content in the salt treatments. The tolerant accessions accumulated greater amounts of Na⁺ in the shoots and less in the roots compared with the salt-sensitive accessions. The shoot K⁺, K: Na ratios, and K⁺ versus Na⁺ selectivity were lower in the salt-tolerant accessions compared with the salt-sensitive accessions; the reverse was true for their roots. Contributions of Na⁺ and Ca²⁺ to osmotic adjustment were much higher in the two salt-tolerant accessions than in the salt-sensitive ones.
It has been established that there is a great deal of variation for salt tolerance in linseed. The degree of salt tolerance of this crop does not vary during ontogeny. The physiological basis of salt tolerance of this species appears to be associated with the inclusion of Na⁺ in the shoots.     

Effect of Sowing Season and Seeding Rate on the Morphological Traits and Yields in Pea Cultivars of Differing Leaf Types

Determination of optimal N-fertilization rates, N_OR , for crop production that minimize risk of environmental degradation require accurate application of a response model. Several models are available to describe crop yield response to N fertilization. The objective of this work was to compare the relative accuracy of a quadratic, f(N _Q), a modified Mitscherlich, and tanh( N ) models on 48 data sets. Data were collected from a Tara silt loam (fine-silty, mixed, frigid Pachic Udic Haploboroll) over a 6-year period using two maize ( Zea mays L.) hybrids and four tillage treatments, mouldboard plough, chisel plough, ridge tillage and no-tillage. In about one-third of the cases, all models performed about equally well. Generally, the tanh( N ) and modified Mitscherlich models gave better fit between N rate and grain yield data. The N_OR, ranged from about 140 to 170 kg ha⁻¹ for the modified Mitscherlich model, 136 to 184 kg ha⁻¹ for the tanh( N) function, and 124 to 173 kg ha⁻¹ using the f(N _Q) model. Estimated grain yields at these rates ranged between 6.58 ± 1.30 to 7.59 ± 1.69 Mg ha⁻¹ for the 90-day Minnesota maturity rated (MR) hybrid and between 7.52 ± 2.40 to 8.72 ± 1.70 Mg ha⁻¹ for the 95-day MR hybrid.     

Breaking Uniculm Growth Habit of Spring Cereals at High Latitudes by Crop Management. II. Tillering, Grain yield and Yield Components

Long days at high latitudes inhibit tillering of cereals and hence seeding rates of 500–700 seeds m⁻² are commonly used for spring wheat, barley and oats in Finland. Costs could be reduced by using a lower seeding rate in combination with crop management to produce more head-bearing tillers m⁻². This study was designed to assess possibilities of breaking the uniculm growth habit of spring cereals by (1) lowering the seeding rate from 600 to 300 seeds m⁻² and (2) manipulating tiller growth with early mechanical treatments to the crop (rolling, cutting) or chemical applications (foliar urea, CCC and GA). A low seeding rate and early application of foliar CCC at high latitudes, under good moisture conditions prior to heading, promoted 20% more head-bearing tillers and 6% higher grain yield than standard management practices. However, cultivars differed in their response to CCC. The advantageous effects of CCC at a low seeding rate were attributed to increase, over the controls, in contribution of head-bearing tillers to grain yield in wheat (cultivar Heta ), but more grains per head in oats (cultivar Veli ). Varietal recommendations for use of low seeding rate in combination with early CCC spraying should be examined further.     

Effects of Seeding Rate on Growth Duration and Accumulation and Partitioning of Dry matter in Oats

Crop management influences considerably the three components of grain yield, growth duration, growth rate, and harvest index (HI). Effects of seeding rate on these yield components in oats ( Avena sativa L.) was assessed in field experiments at the Viikki Experimental Farm, University of Helsinki, Finland (60°13'N) in 1991 and 1992. Three Finnish oat genotypes were evaluated; a long-strawed landrace cultivar, a moderately long-strawed modern cultivar, and a semi-dwarf breeding line. The following traits were measured: grain yield, days from sowing to yellow ripeness, number of tillers on main shoot, phytomass, vegetative phytomass, and their growth rates (PGR and VGR, respectively), panicle weight and its filling rate (PFR), HI, leaf area index (LAI), and at intervals, dry-matter accumulation in leaves and straw.
Increases in seeding rate significantly decreased growth duration and PGR of individual plants but increased PGR on a ground area basis. Seeding rate did not, however, affect HI. When seeding rate was increased from 200 seeds m⁻² to 500 seeds m⁻², reductions in vegetative phytomass, panicle weight, VGR, and PFR for individual plants ranged between 20 and 40 %, depending on genotype. At ≥600 seeds m⁻² differences in these components between seeding rates were modest. However, PGR, VGR, and PFR per unit ground area increased with increasing seeding rates up to 600–700 seeds m⁻². Moreover, the higher the seeding rate, the higher the peak LAI (2.7 maximum) and the earlier the canopy closure. Hence, our results showed that a seeding rate of 600–700 seeds m⁻², which resulted in uniculm growth habit, is advantageous in terms of grain yield at high latitudes due to higher biomass accumulation and subsequently greater interception of PAR.     

Einfluß des Lichtangebotes auf das Wachstum und die biologische Stickstoff-Fixierung von Weißklee (Trifolium repens L.)

Influence of light quantity on growth and biological nitrogen fixation of white clover ( Trifolium repens L.)
The influence of photon irradiance (E_p; 100 to 500 μmol m⁻² s⁻¹) and of the photoperiod (16 or 11 h) on growth and nitrogenase activity of nodulated white clover plants was studied in growth chambers at two nitrate levels (1.0 and 7.5 mM NO₃⁻).
Total dry mass production, the root proportion and nitrogenase activity increased with increasing E_p and photoperiod. Nitrogenase activity generally increased proportionally to root mass. Only at low E_p (100 μmol m⁻² s⁻¹) and under a short photoperiod (11 h) was the specific nitrogenase activity per unit root mass reduced. An abrupt change in E_p led to a rapid and parallel change in nitrogenase activity and relative growth rate.
A higher NO₃⁻ concentration in the nutrient solution (7.5 mM) led to a marked decrease in specific nitrogenase activity, but increased growth between 200 and 500 μmol m⁻² s⁻¹ during early development only. At 100 μmol m⁻² s⁻¹, there was no growth response to nitrate, although its effect on nitrogenase activity was more marked than at a higher E_p.
The results show that with changing light quantity, biological nitrogen fixation of white clover adapts to the existing demand for nitrogen and does not limit growth except during early development, even when light supply is low.     

Relationship Between Ion Accumulation and Growth in Two Spring Wheat Lines Differing in Salt Tolerance at Different Growth Stages

A salt-tolerant line, S24, of spring wheat was compared with a salt-sensitive line, Yecora Rojo, in sand cultures at four different growth stages, i.e. germination, seedling, tillering and booting, under greenhouse conditions. The NaCl treatments used were 0 or 125 mol m⁻³ in full strength Hoagland's nutrient solution. S24 exceeded Yecora Rojo in biomass or grain yield at the tillering and booting stages, but these lines did not differ at the initial growth stages, i.e. germination and seedling. The growth performance of the two lines at different growth stages was positively related to the pattern of accumulation of cations and anions. The superiority of S24 to Yecora Rojo at the two later growth stages was related to its relatively low accumulation of Na⁺ or Cl⁻ and high accumulation of K⁺ in leaves. The former line also maintained higher leaf K/Na ratios, Ca/Na ratios, K versus Na selectivities and Ca versus Na selectivities than the latter particularly at the tillering and booting stages. Salt tolerance in spring wheat, in this study, is found to be age-dependent. The booting stage has been found as one of the most appropriate growth stages where maximum differentiation in salt-tolerant and salt-sensitive lines occurred. As is evident from previous studies with spring wheat, in the present study there is a positive correlation between partial exclusion of Na⁺ or Cl⁻¹ from the tissues and maintenance of high tissue K/Na and Ca/Na ratios, and K versus Na and Ca versus Na selectivities, and salt tolerance of this crop.     

Influence Of Tillage On Soil Aeration

Air- porosity of soil can be altered by tillage. Therefore, it plays a significant role in protecting plants against deficient aeration during critical periods of their life cycle. The effect of five tillage treatments (mouldboard, cultivator, rotary tiller, wedge and zero tillage) and three mulch treatments (paddy straw, rice husk and bare) on the soil oxygen diffusion rate (ODR) during the various growth phases of peanut crop ( Arachis Hypogaea L.) were investigated on a lateritic sandy loam soil (utilsol). These experiments were conducted for two consecutive seasons. ODR values were higher in tilled plots. Among tillage treatments, the highest ODR was recorded under mouldboard (60.51 × 10^-8 g cm^-2 min^-1), followed closely by cultivator (57.65 × 10^-8g cm^-2 min^-1), and it was lowest under rotary tiller (46.29 × 10^-8 g cm^-2 min^-1). During the later growth stages and also in lower soil depths, the differences between the values of ODR narrowed down. Among mulch treatments, plots with rice husk (53.98 × 10^-8 g cm^-2 min^-1), had the higher ODR values. Bulk density was lower, whereas total and aeration porosity were higher, under mouldboard and cultivator. Soil temperatures were also higher under mouldboard and cultivator tilled plots.