Effect of Mycorrhizal Infection on Phosphorus Efficiency of Maize (Zea mays L.) Cultivars

Phosphorus is considered as one of the least available plant nutrients found in the rhizosphere. The large variation in phosphorus acquisition efficiency of different crop cultivars provides opportunities for screening cultivars that perform well on low phosphorus soil for sustainable agriculture. To assess phosphorus efficiency of maize cultivars viz.: Paras and JH 3459, a field experiment was conducted for 2 years at Indian Institute of Technology, Kharagpur, India on sandy loam soil, having pH 5.1, organic carbon 4.1 g kg^?1 soil and as low as 11.2 kg ha^?1 available phosphorus. Phosphorus was applied at a rate of 0 (low) and 400 kg ha^?1 (high) with and without the application of fungicide Benomyl at 500 kg ha^?1 for eradication of arbuscular mycorrhiza. Maize plants were harvested at 24, 48, and 74 days after sowing and final harvest was taken at maturity. In low phosphorus soil without Benomyl, cv. Paras produced 29, 18, and 69 %, while cv. JH 3459 produced 19, 9, and 57 % of their maximum shoot dry weight at 24, 48, and 74 days after sowing, respectively during the first year and the trend was same during the second year. The results indicate that relative shoot dry weight varies with growth stages and therefore, grain yield should be used to assess phosphorus efficiency. At maturity, maize cv. Paras produced 91 and 80 % while JH 3459 produced 71 and 60 % of their maximum grain yield during the first and second year respectively, proving that cv. Paras was more phosphorus efficient than cv. JH 3459. Root growth of both the cultivars was restricted under phosphorus deficiency conditions; however, cv. Paras produced 1.4–2.6 times more root length than cv. JH 3459 at different growth stages. Cultivar Paras had lower phosphorus influx than cv. JH 3459, but it was more phosphorus efficient because of more roots, lower internal phosphorus requirement and higher root length/shoot dry weight ratio. Application of Benomyl was completely effective in suppressing arbuscular mycorrhiza infections up to 48 days after sowing. Its effect started diminishing thereafter and some infection occurred, which however was significantly less than that observed in untreated plots. Thus, the yield difference between Benomyl treated and untreated plots can be attributed to arbuscular mycorrhiza. In low phosphorus soil, Benomyl application reduced the growth of cultivars by 12–45 % and the maximum reduction of growth was at 48 days after sowing. However, in high P soil, Benomyl application had no significant effect on dry matter yield of the cultivars.     

Effect of Nitrogen Fertilizer on Grain Yield and Nitrogen Use Efficiency in Corn (Zea mays L.) Hybrids Under Irrigated Conditions

In order to study the effect of nitrogen rates on grain yield and nitrogen use efficiency of corn (Zea mays L.) hybrids, a field experiment was conducted in south-western Iran during 2011–2012. The experiment was split-plot with RCBD arrangement in three replications. Main plots consisted of four nitrogen rates (0, 90, 180 and 260 kg N ha^?1) and four corn hybrids (Sc.704, Sc.640, Mobeen and DKC6589) were placed in sub-plots. Results indicated that the effect of nitrogen, hybrids and their interaction on corn grain yield was significant. Increase in nitrogen rates from 0 to 90, 180 and 260 kg N ha^?1 increased the mean grain yield studied hybrids by 42.6, 55 and 58 %, respectively. DKC6589 hybrid and Mobeen had the highest and lowest grain yield among studied hybrids. Higher grain yield in DKC6589 was due to higher number of grains per ear and 100-grain weight. The results of step-wise regression coefficients also indicated that number of grains had the maximum contribution in grain yield. As compared to grain yield of Mobeen and Sc.640 hybrids at the levels of 180 and 260 kg N ha^?1, DKC6589 hybrid yield was more in the treatment of no nitrogen. The maximum grain yield was obtained in DKC6589 hybrid and 180 kg N ha^?1. Increase of nitrogen up to 260 kg N ha^?1 led to the significant increase in grain yield of 640 hybrid, but in other hybrids, increase of nitrogen up to more than 180 kg N ha^?1, slightly decreased the grain yield. There was genetic variation for nitrogen use efficiency. It is possible to select hybrids with higher nitrogen use efficiency to reduce the fertilization. Positive and significant relation between grain yield and nitrogen use efficiency was marked. DKC6589 hybrids as compared to other hybrids had more nitrogen use efficiency and agronomic nitrogen use efficiency in lower amount of fertilizer. Generally, it seemed that DKC6589 hybrid had all ideal traits of implantation in the region as the potential of its grain yield was very high.     

Physiological Indices,Phenological Characteristics and Trait Evaluation of Canola Genotypes Response to Different Planting Dates

To manage planting date based on optimal compatibility to the environmental condition a split plot experiment based Randomized Complete Block Design with three replications was carried out. Four planting dates (November 6th and 21st, December 6th and 21st) in main plots and four genotypes (Hyola401, PP401, RGS003 and Option500) in subplots were studied. According to analysis of variance results, grain yield, yield components and biological yield were significantly affected by planting date, genotypes and interaction effect. The first planting date (November 6th) had maximum grain yield (2611.6 t ha^?1) and after it another planting date showed decrease in amount (13.74, 31.36 and 41.97 % respectively). First planting date was superior in physiological index as compared to the other planting dates. Hyola401 hybrid, due to the fact that it had a higher leaf area index (3.51), total dry matter (1248.91 g m^?2), crop growth rate (21 g m^?2 day^?1), net assimilation rate (7 g m^?2 day^?1), relative growth rate (0.064 g g^?1 day^?1) and maximum grain yield, was seen to be the most adaptable genotype. Hyola401 hybrid at first planting date germinated in shortest time (5.8 day) had the highest flowering duration (24.0 day) and long days to ripening (154.0 day). Finally according to the results of the present work, sowing of Hyola401 hybrid on 6th November was recommended as suitable planting date.     

Efficient Nitrogen and Water Management for the Soybean–Wheat System of Madhya Pradesh,Central India,Assessed Using APSIM Model

A series of long-term simulations were carried out to investigate alternative management practices to increase grain yields of soybean and wheat by optimizing sowing dates, nitrogen (N) and water requirements, along with complimenting farmyard manure (FYM) as a N source in the soybean–wheat cropping system of Madhya Pradesh. The APSIM simulation study showed that the mean soybean yield ranged from 1.0 to 1.6 t ha^?1 for the different dates of sowing. The average wheat grain yield was 3.2–3.9 t ha^?1, whereas, the crop sown on 15 November gave the highest yield. In this region, there is a potential to increase soybean and wheat yields by 0.6 and 2.2 t ha^?1, respectively. Among the various irrigation practices simulated, five irrigations of 60 mm at 20 days interval was the best option for wheat. Application of 16 t FYM ha^?1 to soybean produced 50 % higher wheat yield than the same amount of FYM applied to wheat. The wheat yield obtained from inorganic application of N was at par with that obtained from the application of integrated and organic sources. However, the amount of N loss from the integrated use of fertilizer N was lower than that from the current recommended practice for the region. Application of FYM alone or in combination with inorganic fertilizer maintained higher soil organic carbon concentration as compared to the application of inorganic fertilizer alone. Thus, the model provided a mean of evaluating alternative crop N and water management options for effectively managing the soybean–wheat cropping system.     

Mechanisms of Differential Manganese Uptake Efficiency in Winter Cereals at Generative Phase

Plant species as well as cultivars of the same species differ in their Mn efficiency. This paper studied the differential Mn efficiency in relation to Mn dynamics in the rhizosphere and root shoot relations of one durum wheat (cultivar PDW 291), four bread wheat varieties (cv. PBW 509, PBW 636, DBW 17 and PBW 550) and one triticale (cv. TL 2908). The six cultivars were grown in pots under two Mn treatments: (i) 0 mg Mn kg^?1 soil (i.e. soil with 1.54 mg kg^?1 of DTPA-extractable Mn) and (ii) 50 mg Mn kg^?1 soil. Plants were harvested at tillering and 45 days post tillering to record root length (RL), shoot dry weight (SDW), Mn uptake and soil parameters. Under Mn deficiency conditions, PBW 550 produced 47 % of its maximum RL and 58 % of its maximum SDW, whereas PDW 291 produced only 13 and 35 %, respectively. PBW 550 and PDW 291 showed highest and lowest RL/SDW ratio, root surface area and Mn uptake, respectively. Greater Mn concentration difference between bulk soil and root surface in PBW 550 and TL 2908 resulted into 1.4 times higher Mn influx as compared to durum cultivar. It seemed triticale cv. has adaptations to low nutrient availability as indicated by its lowest relative shoot growth rate and highest relative root growth rate.     

Effect of Nitrogen and Defoliation on Assimilate Redistribution and Grain Yield of Maize (Zea mays L.) Under Subtropical Conditions

In order to study the effects of nitrogen levels and defoliation on grain yield, yield components, and assimilate redistribution in maize (single cross 704), a field experiment was conducted in south-west of Iran in 2010–2011. The experiment was split-plot in the form of randomized complete block design with three replications. Main plots consisted of four nitrogen rates (0, 80, 160 and 240 kg N ha^?1) and elimination of some physiological resources including defoliation of upper and lower leaves of the canopy at anthesis stage and control (un-manipulated) were placed in sub-plots. Results indicated that the effect of nitrogen fertilizers and defoliation on grain yield was significant (P < 1 %), but the effect of nitrogen and defoliation interaction on this trait was not. The lowest and the highest grain yield belonged to 0 and 240 kg N ha^?1, respectively. As compared to the un-manipulated treatment, grain yield was 22.2 and 4.2 % lower in defoliation of upper and lower leaves, respectively. Grain yield reduction in defoliation of upper leaves was due to significant reduction of the number of grains and their weight. As the nitrogen rates increased to 160 and 240 kg ha^?1, stem assimilate redistribution increased and somewhat compensated for the effect of defoliation of lower leaves of the maize on its grain yield.     

Bio-efficacy of Herbicides on Performance of Mustard, <Emphasis Type="Italic">Brassica juncea</Emphasis> (L.) and Population Dynamics of Agriculturally Important Bacteria

The bio-efficacy of different herbicide treatments on the performance of mustard crop and its effect on population dynamics of beneficial soil microorganisms like Azotobacter (aerobic and free-living nitrogen fixing bacteria), Bacillus and Pseudomonas (phosphate solubilisation and biocontrol agents) were studied. Higher doses of pendimethalin (@1.0 kg ha^?1) and isoproturon (@1.0 kg ha^?1) had toxic effect on the germination (13.33 and 17.33 m^?2) and emergence of mustard crop and resulted in significantly lower plant population. These treatments resulted in reduction of plant population to the tune of 47.92 and 31.48 % at 30 days after sowing (DAS) and 47.06 and 27.96 % at harvest. Weed free treatment recorded significantly higher seed yield (2781 kg ha^?1) which was about 99 % more than the weedy check. The increase in seed yield with different herbicides was to the tune of 27–73 % over weedy check, except pendimethalin @1.0 kg ha^?1 as pre-emergence (PE). The weedy check plot showed highest population of Azotobacter, Bacillus, and Pseudomonas throughout the observation period. However, among different herbicide treatments, the highest population of Azotobacter and Bacillus was observed with pendimethalin 0.5 kg ha^?1 as PE and that of Pseudomonas with isoproturon 1.0 kg ha^?1 30 DAS at harvest stage.     

Effect of Organic Sources of Nutrients on Tuber Bulking Rate,Grades and Specific Gravity of Potato Tubers

A field experiment was conducted during 2008–2009 and 2009–2010 to investigate the effect of organic sources of nutrients on tuber bulking rate, grades and specific gravity of potato tubers. The experiment consisted 24 treatment combinations with 8 treatment in popcorn [control, recommended dose of fertilizers (N₁₂₀P₂₅K₃₅ kg ha^?1), farmyard manure equivalent to 120 kg N ha^?1, leaf compost equivalent to 120 kg N ha^?1, vermicompost equivalent to 120 kg N ha^?1, farmyard manure equivalent to 90 kg N ha^?1, leaf compost equivalent to 90 kg N ha^?1 vermicompost equivalent to 90 kg N ha^?1 in succeeding crop of potato, three treatments [control, farmyard manure equivalent to 60 kg N ha^?1 and farmyard manure equivalent to 90 kg N ha^?1] were superimposed on the different treatments of pop corn. It was found that the application of farmyard manure equivalent to120 kg N ha^?1 to pop corn and farmyard manure equivalent in 90 kg N ha^?1 in potato gave the highest values of tuber bulking rate, specific gravity, number of large–sized (A–grade) and medium–sized tubers (B–grade) and total tuber yield followed by vermicompost equivalent to to 120 kg N ha^?1. Farmyard manure equivalent to 90 kg N ha^?1 to potato also recorded the higher bulking rate, tuber yield, specific gravity and a number of large sized tubers (A– grade and B–grade) as compared to the farmyard manure equivalent to 60 kg N ha^?1. The available N, P, and K in soil also improved with the application of organic manures.     

Study of Optimum Time Span for Distinguishing Rumex spinosus in Wheat Crop Through Spectral Reflectance Characteristics

Using the inherent spatial and temporal variability within a field to manage farm operations is called precision agriculture. This is a site-specific approach which can reduce input costs and results in higher crop productivity, profitability and lesser environmental pollution. Remote sensing provides a means for the development of weed maps by detecting the location of weeds within an agricultural field, so that site-specific/need based herbicide can be applied. Reductions in herbicide use as a result of this practice reduce management costs for farmers and promote environmental friendliness. The results revealed a decreasing trend in the number of tillers, effective tillers, number of grains per ear, 1,000-grain weight and grain yield of wheat with increasing population densities of Rumex spinosus (from 3 to 12 plants m^?2). Highest grain yield of wheat (5.75 tonnes ha^?1) was recorded under solid stand of wheat and lowest grain yield was recorded in treatments having 12 plants of R. spinosus. Higher radiance ratio and NDVI values were recorded in solid stand or pure wheat treatment and minimum under solid weed plots. It was observed that by using radiance ratio and NDVI, pure wheat can be distinguished from pure populations of R. spinosus after 30 DAS. It remains distinguished upto 120 DAS. Different levels of Rumex populations can be discriminated amongst themselves from 60 DAS onwards.     

Growth,Physiology and Biochemical Responses of Two Different <Emphasis Type="Italic">Brassica</Emphasis> Species to Elevated CO<Subscript>2</Subscript>

In an open top chamber study, two contrasting Brassica cultivars from two different species were grown under two distinct levels of CO₂ concentration, 550 µmol mol^?1 (elevated) and 390 µmol mol^?1 (ambient). CO₂ enrichment showed significant increase in growth, leaf area and dry matter production in both the species. The continuous higher rate of photosynthesis (36.2 % in RH-30 and 27.3 % in Pusa Gold) under elevated CO₂ condition attributed to the increased generation of foliage and enhancement in stem and root growth which is also evidenced by higher net assimilation and relative growth rate. The increase was highest at flowering stage with a concomitant increase in net photosynthetic rate but showed reduction in respiration rate and stomatal conductance. The increase in net photosynthesis further resulted in higher accumulation of sugars, non-structural carbohydrates and starch in leaves in elevated CO₂ grown plants. Larger accumulation of biomass was observed in root as compared to other plant parts. However, the species specific differences were reflected in the accumulation of biomass, grain yield and gas exchange phenomena, wherein the greater response was invariably found in RH-30 (Brassica juncea) as compared to Pusa Gold (Brassica campestris). The present study may prove beneficial to understand crop responses to future climatic conditions and suggest efficient adaptive strategies from crop management perspectives.     

Effect of In situ Recycling of Sugarcane Crop Residues on Soil Enzyme Activities Under Soybean–Maize System

An investigation was carried out by conducting a field experiment at the farm of the Mahatma Phule Krishi Vidyapeeth (MPKV), Rahuri. The significant grain yield of soybean (37.5 q ha^?1) and maize (49 q ha^?1) were observed in the treatment receiving 100 % recommended doses of Nitrogen, Phosphorus and Potassium (NPK) + in situ compost of crop residues, pressmud compost (T₆). After harvest of maize dehydrogenase activity, acid phosphatase, β-glucosidase and urease were significantly improved in T₇ treatment as compared to other treatments. However, fluorescein diacetate activity and alkaline phosphatase were significantly greater in T₆ treatment in post-harvest soil samples of maize. In the post-harvest soil of maize the bacterial and actinomycetes population were greater in the treatment receiving in situ decomposition of sugarcane crop residues + 100 % recommended dose of NPK (T₃). The fungal population after harvest of maize was found maximum in treatment T₇. The total organic carbon was significantly correlated with dehydrogenase (r = 0.65, P < 0.01), fluorescein diacetate (r = 0.71, P < 0.01), acid phosphatase (r = 0.66, P < 0.01), β-glucosidase (r = 0.65, P < 0.01), and urease (r = 0.57, P < 0.01). There was a significant correlation (r = 0.77, P < 0.01) between TOC and soybean yield, and between total organic carbon and maize yield (r = 0.98, P < 0.01). The result suggest that in situ recycling of sugarcane crop residues and the industrial wastes with suitable interventions like use of bioinoculum, phosphatic fertilizer and urea may help for improving better crop productivity and soil biological activities.     

Effects of Resource Conservation Practices on Productivity,Profitability and Energy Budgeting in Maize–Wheat Cropping System of Indian Sub-Himalayas

Resource conservation issues have drawn the attention of scientists to devise innovative tillage and crop establishment techniques for higher productivity in small holder farming systems in the tropics but relatively less attention has been given in rainfed sloping lands of the Indian sub-Himalayan (sub-temperate) regions. To investigate these issues, an experiment was conducted on resource conservation practices under rainfed conditions for 5 years (June 2007–May 2012) at Dehradun, Uttarakhand in the Indian Himalayan region. Four treatments, 1. 100:60:40 kg N:P₂O₅:K₂O + conventional tillage (CT) + chemical weeding + PANICUM vegetation strip (T₁); 2. FYM (5 t ha^?1) + minimum tillage (MT) + 1 weed mulch (30 DAS) @ 0.52 t ha^?1 + PALMAROSA vegetation strip (T₂); 3. FYM (5 t ha^?1) + vermi-compost (1.0 t ha^?1) + MT + 2 weed mulch (25 and 50 DAS) @ 1.47 t ha^?1 + PALMAROSA vegetation strip (T₃) and 4. FYM (5 t ha^?1) + vermi-compost (1.0 t ha^?1) + poultry manure (2.5 t ha^?1) + MT + 3 weed mulch (20, 40 and 60 DAS) @ 2.18 t ha^?1 + PALMAROSA vegetation strip (T₄). The results showed that resource conservation treatments (T₄, T₃ and T₂) had significant (P ≤ 0.05) multiple benefits as compared to traditional agriculture treatments (T₁). T₁ gives the highest yield of maize whereas T₄ gives highest yield of wheat. For the maize–wheat cropping system, mean wheat equivalent yield (WEY) was ~16 % higher in T₄ than T₁. Mean runoff was ~30 % lesser and mean soil loss was ~34 % lesser in T₄ as compared with T₁. Similarly, mean soil moisture conservation for rainfed wheat was ~31 % higher in T₄ than T₁. Mean carbon retention potential increased by ~53 % which subsequently increased mean soil quality index (SQI) by ~25 %. Mean energy productivity increased by ~70 % and mean energy intensiveness decreased by ~56 % in T₄ than T₁. Treatment T₁ (2,560 MJ^?1) emerged to be the most energy intensive system as compared to T₄ (1,113 MJ Rs.^?1). On an average, T₄ had 7 % higher net returns than T₁ and in terms of net returns per tonne of soil loss, T₄ was the best treatment (Rs. 4,907). Therefore, resource conservation system (PALMAROSA as a vegetation strip along with organic amendments, FYM, vermi-compost, poultry manure and weed mulch under minimum tillage) had significant positive impact on yield, resource conservation and energy saving and may be introduced as a substitute of conventional system in the Indian sub-Himalayas and under similar climatic and edaphic conditions.     

Effects of Tillage and Residue Management Practices on Soil and Root Parameters in Soybean (<Emphasis Type="Italic">Glycine max</Emphasis>)–Wheat (<Emphasis Type="Italic">Triticum aestivum</Emphasis>) Cropping System

A field study was conducted during 2009–2011 to investigate the effect of tillage, crop establishment and residue management practices on soil and root parameters in soybean-wheat cropping system. The experiment was conducted with 4 main plot treatments of tillage and crop establishment techniques as conventional tillage-flat (CT-F), zero tillage-flat (ZT-F), conventional tillage-bed (CT-B) and zero tillage-bed (ZT-B); and 4 sub plot treatments of residue application as control, wheat residue (3 t ha^?1), soybean residue (3 t ha^?1) and soybean + wheat residue (3 t ha^?1 each). The infiltration rate was significantly higher with ZT-F (1.22 cm h^?1) and wheat + soybean residue application (1.16 cm h^?1). ZT-F and ZT-B recorded higher mean weight diameter and geometric mean diameter at 0–10 cm than that of CT-F and CT-B. The percentage of micro-aggregate was higher with CT-F and CT-B at all depths while the macro-aggregate was high with ZT-F and ZT-B up to 30 cm soil depth. The microbial biomass carbon in ZT-F and ZT-B was 216.3 and 214.6 µg g^?1 of soil, respectively which was significantly higher than that of CT-F and CT-B. The wheat + soybean residue application recorded 19.6 % higher MBC than the control. Among the tillage treatments, ZT-F performed well with regard to root length density as 2.38 and 1.11 cm cm^?3, root surface area as 0.67 and 0.36 cm² cm^?3, root volume density as 19.22 and 8.26 × 10^?3 cm³ cm^?3 and average root diameter as 1.06 and 0.81 mm by soybean and wheat, respectively. Similarly, wheat + soybean residue also performed better than the no residue treatment.     

BOOK REVIEWS

After clearfeliing and removal of sawlogs and waste wood from a 33-year-old crop of radiata pine, a site on the central tablelands of New South Wales contained an estimated 222 kg ha ' of nitrogen in above-ground litter and logging slash, and 8746 kg ha^?1 in the soil. Broadcast burning of the litter and slash removed 139 kg ha^?1 of nitrogen, but had no measurable effect on the organic matter content of the soil. Hand raking removed 212 kg ha^?1 of nitrogen from the litter and slash, as well as approximately 1 cm of topsoil, containing at least 124 kg ha^?1 nitrogen.

It was concluded that on this site the commonly used technique of windrow raking of logging slash and litter before replanting was likely to have a greater effect on site nutrient capital than broadcast burning. Neither practice had an appreciable impact on total site reserves of nitrogen, since very large quantities are contained in the mineral soil. However, since little is known of the availability of these soil reserves to the replanted crop, it would be prudent to modify existing techniques so as to minimise their impact on the above-ground nutrient capital. It is suggested that a raking operation which removed only the woody debris would probably allow sufficient access for replanting, and would leave most of the nutrient-rich fine litter and topsoil intact.     

Biomass and nutrient distribution in relation Pine in relation to previous land use I. Biomass

Above-ground biomass data are compared for 21-year-old radiata pine stands on three sites which had different types of land use prior to plantation establishment. The three sites, previously under native forest, grazed pasture and a pasture site subsequently used for crop production (cultivated) formed a continuous section of plantation in the 1968 age class. Biomass equations were developed for each tree component in relation to stem diameter for each site. There were no significant differences between sites in the coefficients for stemwood and bark, but different coefficients were required to relate stem diameter to the biomass of branches in the dead crown and foliage in the lower live crown. Stands on previously cultivated pasture (pasture followed by crops) accumulated 362,745 kg ha^?1 in the above-ground biomass; 40% and 13% more than the ex-native forest (259,183 kg ha^?1) and ex-pasture (320,055 kg ha^?1) sites, respectively. Trees on the previously cultivated pasture allocated a larger proportion of the total biomass to branches (17.4%) compared with the ex-native forest and ex-pasture trees (11.1%). This is attributed to reduced stocking and enriched soil resulting from different previous land use practices. The high frequency of multi-leadered trees in the ex-cultivated pasture increased the non-merchantable components to 26.7% of the total biomass.     

Phenotypic and Molecular Characterization of Alleles of Grain Quality Genes in Bread Wheat Genotypes

Grain quality is an important determinant of market value of wheat. Identification of the genes that influence grain quality traits and estimation of effects of alleles of these genes can improve the effectiveness of wheat breeding. Sixty-four bread wheat cultivars from six different agro-climatic zones of India and eleven Australian cultivars were analyzed for the prevalence of Puroindoline (Pin) hardness mutations and Storage Protein Activator (SPA) alleles for detecting allelic diversity among these varieties. Most of the Australian genotypes had soft or semi hard textured grains and amplified both Pina and Pinb genes. In Indian genotypes, most of the genotypes had hard grain texture and the null mutation of Pina and the wild type Pinb allele (Pina-D1b/Pinb-D1a) was the most frequent combination in the Indian wheat germplasm. Predominance of Spa gene was observed in both Australian and Indian genotypes and all these genotypes recorded high grain protein content as compared to genotypes which are having null allele for SpaB gene. This study can provide useful information for the improvement of wheat quality in selecting parental lines for crossing to maximize diversity at these loci and enhance the effectiveness of molecular marker assisted crop breeding.     

Long-term estimates of live above-ground tree carbon stocks and net change in managed uneven-aged mixed species forests of sub-tropical Queensland,Australia

Estimates of carbon stocks and their annual change for extensive Australian sub-tropical forests are based on indirect estimates or on data derived from temperate forests. We estimated live above-ground tree carbon (LAC) stocks at landscape level from 355?000 measurements of 94?127 tree stems from 604 permanently monitored plots representing 2.6 million ha of managed uneven-aged mixed-species native forests in sub-tropical Queensland. These plots were established between 1936 and 1998 and re-measured every 2 to 10 years up to 2011. Landscapes were represented by 16 broad vegetation groups growing across a mean annual rainfall range of 500 to 2000 mm. Landscape-mean LAC stocks varied from 20.8 ± 4.3 t C ha^?1 in inland eucalypt woodlands to 146.4 ± 11.1 t C ha^?1 in coastal wet tall open forests. Landscape maximum LAC stock, defined as the mean of maximum LAC stocks over the entire measurement history for a specified landscape under prevailing environmental conditions and disturbance regimes, including sustainable forest management, ranged from 34.0 ± 7.2 t C ha^?1 in inland eucalypt woodlands to 154.9 ± 19.4 t C ha^?1 in coastal wet tall open forests. Annual live above-ground net carbon flux (C-flux) across all forests types ranged from 0.46 to 2.92 t C ha^?1 y^?1 with an overall mean of 0.95 t C ha^?1 y^?1 (n = 2067). Comparison of our results with Intergovernmental Panel on Climate Change (IPCC) estimates shows that in all cases, except for the sub-tropical steppe, the IPCC over-estimated stocks by between 13% and 34%. Conversely, the IPCC estimated C-fluxes were between 14% and 40% less than the Queensland estimates. These results extend statistically valid estimates of landscape LAC stocks and fluxes to the sub-tropical regions of Australia.     

Evaluating Linear and Non-linear Genotype–Environment Interactions in Pearl Millet

The nature of genotype–environment (GE) interactions was investigated for two F₁ hybrids and eight open pollinated varieties (OPVs) of pearl millet for grain yield in 12 environments spread over 2 years (2010 and 2011) across the pearl millet growing belt of Sudan. The joint regression analysis showed significant linear and non-linear GE interactions corresponding to heterogeneity and remainder mean squares. However, the GE interactions of all genotypes except PGO9PM1 were explained by the linear regression model. Six OPVs and hybrid PGO9PM3 showed general adaptation with b ≈ 1.0 and non-significant remainder mean squares. Of these genotypes, while hybrid PMO9PM3 was the highest yielding (917 kg ha⁻¹) farmers could adopt any genotype by trading off between their desirable traits such as mean grain yield, earliness, fodder yield and quality criteria etc. Two varieties (ISC-III and MCNELC), were specifically adapted to below average environments with their mean grain yields non-significantly different from the other six OPVs. The highest yielding hybrid PMO9PM1, on the other hand, showed specific adaptation to favourable environments but also had large remainder mean squares. More complex models such as quadratic, 2-intersecting-straight lines, 3-intersecting-straight lines were fitted which, however, could not account for the large remainder mean squares. A 3-lines model with quadratic component in the higher yielding segment of environments was found adequate showing that the upper threshold value for the hybrid was not reached and it would continue responding to higher yielding environments.

     

Managing wood production from small grower acacia hybrid plantations on eroded soils in central Vietnam

An experiment in a second rotation acacia hybrid (Acacia mangium × A. auriculiformis) clonal plantation in central Vietnam examined factors determining total wood production and its apportionment to sawlog and pulpwood. Growth and stand characteristics were compared with those in nearby plantations owned by small growers. The experimental site was on sloping land damaged and eroded by war and previous land use. The soil was shallow, with 20–30% laterised stones by volume and had lost part of the A horizon. Mean annual increment (MAI, in standing merchantable volume over bark) of the first rotation at age 8.8 years was 17 m³ ha^?1 y^?1. In the second rotation at age 7.6 years it was 20 m³ ha^?1 y^?1. Application of P fertiliser at three rates ranging from 14 to 86 kg ha^?1 increased stem diameter over the second rotation although stand volume response to P was not significant by rotation end. Potassium (14 kg ha^?1) gave no growth response. Growth rate was similar under weed control by herbicide and manual means. MAI increased progressively from 16.5 m³ ha^?1 y^?1 at the hilltop to 25.0 m³ ha^?1 y^?1 at the lowest part of the experiment; slope position influenced growth more than management practices. Key soil properties, pH, N, Bray-1 P and organic C were maintained from the first to the second rotation. With simple management practices including conservation of site organic matter and early stand management, appropriate for local small growers, the second rotation yielded 46% of harvested volume as sawlogs and the balance as pulpwood. Although small growers achieved similar growth rates, their current management regime does not yield sawlogs. They can influence the log categories produced and stand value through changes to stocking rate, stand management and rotation age.     

HIGHER FORESTRY EDUCATION IN AUSTRALIA

The results of three field trials which were established in 1976 to determine the feasibility of increasing wood production of Pinus radiata by fertilisation of thinned stands are described after four years of growth following the fertilisation treatments. The stands of about 20 years of age were producing an average of 14 m³ ha^?1 stem-wood per year.

The extra volume of wood growth resulting from fertilisation averaged 4.2 m³ ha^?1 a¹ for all sites, and 5.9 m³ ha^?1 a^?1 for the two most responsive sites, the latter being 37% over that obtained from unfertilised stands. Fifty per cent of the extra volume was added to the largest one-third of trees in the stands. A dominant tree of diameter (bhob) 27.0 cm in 1976 became 30.7 cm in 1980 if unfertilised and 32.8 cm if fertilised, an increase of 2.1 cm.

The responses obtained were inversely proportional to both the relative growth rates of unfertilised stands following thinning, and to the nitrogen concentration in the foliage of unfertilised trees measured in the year following fertilisation. Some soil/plant relationships have been examined for nitrogen, phosphorus, potassium and sulphur.

Fertilisation at this age appeared to at least ‘break-even’ if costs were amortised at an interest rate of 6%. However, fertilisation may also be a useful means of increasing yields at relatively short notice and allow increased flexibility in harvesting and other forest operations.