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.     

REVIEWS

Over a wide range of conditions fine fuel re-accumulation after fire in eucalypt forests is well described by equations of the form X_t = X_ss (l-e^?kt)

where X_t is the weight (t ha^?1) of litter accumulated at time t(yr), X_ss is the weight of accumulated litter under steady-state conditions, and k is a decomposition rate constant (yr^?1). Decomposition constants ranged from 0.11 to 0.31 yr^?1, and steady- state litter accumulations varied between 11.1 and 29.4 t ha^?1.

In many types of eucalypt forest, litter re-accumulates to dangerous (from a fire control point of view) weights in 3–6 years, thus severely limiting the period during which prescribed burning provides protection from wildfire. The rapid rate of litter re-accumulation is mostly due to a marked decrease in the total amount of litter decomposing (relative to rates of litter input), rather than to any fire-induced reduction in the rate of decomposition. The implications of these findings for fire management in eucalypt forests are briefly discussed.

More quantitative information on the relationships between fuel mass (and other fuel characteristics) and fire behaviour under high to very high fire danger conditions is required to enable better evaluation of the effectiveness of low intensity prescribed burning for fire control. The ecological impacts of prescribed burning regimes, which also need to be considered when devising burning programs, are briefly discussed.     

Eucalyptus growth in relation to combined nitrogen and phosphorus fertiliser and soil chemistry in Tasmania

Two experiments were established to determine the early nutrient requirements for plantations of Eucalyptus globulus (Nabowla site) and E. nitens (Westfield site) in Tasmania, Australia. Nitrogen (N) and phosphorus (P) were broadcast together, 2 and 26 months after planting, at cumulative rates of up to 1200 kg N ha^?1 600 kg P ha^?1. Soil chemistry was characterised at each site in three profiles, and in all plots at the Westfield site. Nabowla has a relatively infertile, poorly structured soil, low in N and P, and receives about 800 mm of rainfall per annum. Growth was very poor without fertiliser, but trees responded rapidly and strongly to added NP. Stem volume increased directly with the rate of applied fertiliser, with no evidence that the response had peaked at the highest rate. Even at the highest rate of NP fertiliser, however, productivity was relatively low (mean annual increment about 15 m ha^?1 y^?1). Establishment of plantations on such sites is unlikely to be economically viable, with or without fertiliser, but fertile ex-pasture sites that are otherwise similar should be considered. Westfield has a relatively fertile, well-structured soil, and receives 1400–1500 mm of rainfall per annum. Response to NP fertiliser was delayed at this site, with first responses measured 33 months after planting. The response in stem volume was sigmoidal in relation to fertiliser rate, with a plateau at an application rate of 400 kg N ha^?1 and 200 kg P ha^?1. This rate of fertiliser is expected to increase mean annual increment from 20 (without fertiliser) to 25 m ha^?1 y^?1. Splitting applications of fertiliser at the highest rate did not alter the growth response.

Although high rates of N and P fertiliser may be required to maximise growth of eucalypt plantations in Tasmania on ex-forest sites, rates required during the first few years might be lower than those reported here if the timing and placement of fertiliser is optimised. Soil chemical analyses were indicative of N and P requirements, and about a third of the variation in growth across the Westfield site was accounted for by natural variability in initial concentrations of total P and exchangeable K in surface soil.     

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.     

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.     

Weed control among planted and direct-seeded Eucalyptus,Acacia and Casuarina with the herbicides diphenamid,oryzalin, clopyralid and fluazifop-butyl

In a glasshouse pot trial, applications of the pre-emergence herbicide oryzalin at rates equivalent to 4 and 8 kg a.i. ha^?1 were toxic to germinating seeds of Eucalyptus maculata, Casuarina glauca and Acacia saligna. The pre-emergence herbicide diphenamid was toxic at rates of 7 and 14 kg a.i. ha^?1 to germinating C. glauca and A. saligna, but not to E. maculata.

Both oryzalin and diphenamid were selective at these rates when applied over newly-planted seedlings of Eucalyptus melliodora, Casuarina cunninghamiana and Acacia baileyana on a former pasture site. Diphenamid gave greater pre-emergence control of grass weeds, while oryzalin was more effective against the broad-leaved weeds. Overall, the most satisfactory long-term weed control and tree response was achieved with oryzalin.

The post-emergence herbicides fluazifop-butyl at 0.6 and 1.2 kg a.e. ha^?1 and clopyralid at 0.25 and 0.5 kg a.e. ha^?1, were mostly selective to the planted seedlings on the former pasture site, but they gave unsatisfactory weed control, probably because of a combination of poor timing of application and a herbicide-tolerant weed flora.     

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.     

Influence of soil pH on the germination and survival of Eucalyptus regnans F.Muell. in southern Tasmania

Alkaline soil conditions present in localised areas shortly after slash burning of a logging coupe in southern Tasmania were found to reduce both germination of Eucalyptus regnans seed and survival of young seedlings. In vitro studies showed that high pH conditions could interfere with the germination of E. regnans seed at otherwise conducive temperatures although the influence of elevated pH on seed viability was reduced at temperatures sufficiently low to maintain seed dormancy. The transition to a detrimental effect appeared to be in the pH range 8.4 to 9.0.

Field and glasshouse trials showed that some of the surface soils could be sufficiently alkaline to have a detrimental effect on seedling establishment, especially where seed was sown very soon after burning although observed effects may not have been due to pH alone. Such soils would nevertheless represent only a small proportion of the total sowing area, with toxicity being limited to a period of a few months following burning.

Although elevation of soil pH by fire is well known, it appears that this as a factor contributing to seedling mortality has been overlooked.     

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.     

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.     

The effect of tree spacing on the production of flowers in Eucalyptus nitens

The effect of spacing on the production of flowers and capsules in Eucalyptus nitens was studied in two spacing trials located in northern Tasmania. Tree density in these trials ranged from 468 to 4216 stems ha^?1. Reproductive structures were collected in litter traps and these data were used to calculate reproductive output on a per tree and per hectare basis. Between 8735 (5-y-old site, 1333 stems ha”¹) to 234098 (13-y-old site, 1082 stems ha”¹) flowers were produced per hectare over a single flowering season at these two study sites at the planting densities expected of a pulpwood plantation. This represented 8 and 211 flowers per tree respectively. As tree density decreased, the production of flowers and capsules increased on both a per-tree and per-hectare basis. It is estimated that the number of flowers per hectare is likely to be anywhere between between 1.4 and 10-fold greater under the spacing expected in sawlog regimes (250 trees ha^?1). This difference in reproductive output between plantations of E. nitens that use different spacing regimes is one of the many factors that need to be considered in assessing the risk of wilding establishment or hybridisation with adjacent native eucalypts.     

Book Review

The effects of three prescribed low intensity fires varying from means of 80 to 209 kWm^?1 within six years on invertebrates in litter/upper soil were assessed. The 8.6 year study was based on 88 934 arthropod specimens, representing 35 ordinal or lower level taxa contained in 3520 pitfall trap samples from a site burnt three times in spring and an unburnt control site within a 30.7 ha area.

The three fires had no discernible effect on total taxa, total non-insects, Araneae (spiders), Acarina (mites), Collembola (springtails), total insects and Formicidae (ants), although activity of the Coleoptera (beetles) decreased significantly after the second and third fires while that of the Diptera (flies) increased over the same period. However, as Coleoptera and Diptera activity on the unburnt control site decreased and increased respectively over the same period, it is uncertain whether the changes in activity were due to the fires or other non fire-related environmental factors. Futhermore, these changes in activity resulted from one or two of the spring fires only, and not all three, further questioning whether the fires were the contributing causal factors.

Three prescribed low-intensity fires in spring appear therefore, not to impact adversely on the activity of major forest litter arthropod groups, although the situation of the Coleoptera and Diptera is less clear due to similar activity on the unburnt control site in both cases. This therefore suggests that any fuel reduction burning in spring be conducted at intervals of not less than three years in order to minimize any impact on litter arthropods. Where a period of drought has occurred, burning should be delayed until the drought period has ended.     

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.     

Screening Diverse Rice (Oryza sativa L) Genotypes for Manganese Efficiency

Soil manganese (Mn) deficiency limits the growth and crop yield. Growing Mn efficient cultivars i.e. the cultivars with high yield at low Mn supply would represent a long term solution and sustainable approach to crop production. To evaluate Mn efficiency of 38 diverse rice genotypes, field experiment was conducted during kharif seasons using Mn deficient (2.20?mg?kg^?1) soil. Typic Ustrochrepts loamy sand soil, treated with 0?kg Mn?ha^?1 (no Mn, low level) and 20?kg Mn?ha^?1 supplemented with two foliar sprays@ 0.5?% MnSO₄ (high level). The relative grain yield i.e. Mn efficiency index varied from 100 to 84?% and relative grain Mn uptake i.e. Mn efficiency from 80 to 53?% among the genotypes and the cultivar PR116 was having highest Mn efficiency index as well as efficiency. On the basis of grain yield and Mn efficiency, genotypes were classified as efficient and responsive (PR116, 3047, PAU201, 3131, 3125, HKR127, 3106, 3129, 3128, 3100 and 3138), efficient and nonresponsive (PR120, PR113, 3126, 3033, 3132, 3056, 3130, 3036, 3109, 3124, 3101 and 3136), inefficient and responsive (3127, PR115, 3133, 3134 and 3142), and inefficient and nonresponsive (PR114, PR118, 3137, PR111, 3108, PUSA44, 3135, 3139, 3140 and 3141). From a practical point of view, genotypes that produce high grain yield at a low level of Mn and respond well to Mn additions are the most desirable because they are able to express their high yield potential in a wide range of Mn availability.     

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.     

Wood properties of Eucalyptus globulus at three sites in Western Australia: effects of fertiliser and plantation stocking

Wood properties of 10-year-old trees in Eucalyptus globulus plantations at three sites in Western Australia were examined. Silvicultural treatments applied at age two years were stocking (unthinned, 1250 stems ha^–1; thinned to 600 stems ha^–1 or 300 stems ha^–1) and nitrogen fertiliser application (0 or 250 kg ha^–1 elemental nitrogen) in factorial combination. The three sites differed markedly in their annual rainfall (620–1100 mm), open-pan evaporation and soil water-holding capacity. Wood cores were collected at breast height from a total of 263 trees (~15 trees for each site-by-treatment combination), and radial samples prepared for analysis by SilviScan to produce radial profiles of air-dry density and microfibril angle (MFA) and modulus of elasticity (MOE), and by radial near infrared (NIR) surface scanning to produce radial profiles of NIR-predicted Kraft pulp yield (KPY) and cellulose content (CC). Sampling interval was 0.025 mm for density and 5 mm for the other properties. For wood property mean values (i.e. wood property averages of each pith-to-cambium sample), sites differed significantly only in air-dry density. The Boyup Brook site, which had low annual rainfall, the lowest climate wetness index and soil water-storage capacity and the slowest diameter growth, had the highest mean wood density (648 kg m^–3), while Scott River, with the highest rainfall, had mean density that was 10% lower. The Wellstead site (low rainfall but highest soil water-storage capacity) was intermediate for density. The only other significant differences for mean wood properties were caused by fertiliser addition, which reduced NIR-predicted KPY from 54.6% (without fertiliser) to 54.1% and predicted CC from 43.7% to 43.1%. Clear radial trends were evident for all wood properties. Density, MOE, KPY and CC all increased from pith to the cambium, while MFA declined. From the innermost (pith) 10% to the outermost (cambial) 10% of the radius, density increased on average by 21%, MOE by 103%, KPY by 9% and cellulose by 11%, while MFA declined by 47%. NIR calibrations developed using the SilviScan and NIR spectral data explained 71% of variance in MOE for an independent set of radial wood samples of E. globulus from Victoria, but less than 50% of variance for density and MFA. Implications for paper pulp and veneer manufacture are briefly considered.     

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.     

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.     

Merchantability of Pinus radiata in relation to previous land use

An integrated thinning operation was carried out in 21-year-old radiata pine stands in the central tablelands of New South Wales to examine the effect of previous land use and associated problems of poor tree form on recovery of merchantable timber. The areas thinned were contiguous sections of plantation which had different types of land use prior to plantation establishment; native forest, cleared grazing land (pasture) and cleared land initially grazed and subsequently cultivated and cropped (cultivated pasture). Total volumes of harvested trees (to 8 cm small end diameter) were estimated (assuming no poor tree form) from regressions relating volume to stem diameter. This estimate was compared with the actual volume of saw logs and pulp wood recovered on site and with merchantable yields predicted using a locally derived Forestry Commission equation.

On-site yields of saw logs plus pulp wood were 143 m³ ha^?1 from the ex-native forest site, 191 m³ ha^?1 from the ex-cultivated pasture site and 210 m³ ha^?1 from the ex-pasture site. This represented a total recovery of more than 90% of the total stem volume to 8 cm small end diameter from ex-native forest and ex-pasture trees compared with 73% from the ex-cultivated pasture trees.

Of the trees harvested, 45% from the ex-native forest site had stem defects compared with 65% from the ex-pasture site and 88% from the ex-cultivated pasture site. These defects reduced the average saw log volume per tree by at least 50% in trees greater than 35 cm DBHOB. In contrast, the yield of pulpwood was similar for deformed and non-deformed trees because some logs which did not meet saw log specifications were down-graded to pulp logs.