Nutrient dynamics of foliar litter in reciprocal decomposition in tropical and subtropical forests

In order to explore the release of nutrients and the effects of global warming on the decomposition rate of forest litter, an experiment is designed to reciprocally decompose forest foliar litter in two sites across climatic zones: Mt. Jianfengling in Hainan Province in the tropics and Mt. Dinghushan in Guangdong Province in the subtropics. The two sites have similar altitudes, soil types, annual mean rainfall and seasonality of dry and wet. The main difference between these two sites is the annual mean temperature with the difference of 3.7°C. Foliar litters of 10 native dominant tree species have been collected respectively from the two sites and divided into single-species litter and mixed litter. They are decomposed reciprocally in the two sites. The results indicate that litter decomposes in the tropical site 1.36–3.06 times more rapidly than in the subtropical site. Apparent Q ₁₀, calculated on the basis of the temperature difference between the two sites, ranges from 3.7 to 7.5. The return amount of N, P and C will increase by 32.42, 1.033 and 741.1 kg/hm², respectively in Mt. Dinghushan in the first year’s litter decomposition under the prevailing temperature condition. Only in Mt. Dinghushan is the correlation between decomposition rate constant and initial litter quality high and significant in the ratio of lignin to N, lignin, the ratio of lignin to P, HLQ and C. This is not the case at Mt. Jianfengling. __________ Translated from Journal of Beijing Forestry University, 2005, 27(1): 24–32 [译自: 北京林业大学学报, 2005, 27(1): 24–32]     

Microbial properties of soils as affected by cropping and nutrient management practices in several long-term manurial experiments in the semi-arid tropics of India

Microorganisms play a critical role in nutrient transformation, soil health and for sustaining the productivity of soils. Effects of long-term cropping, fertilization, manuring and their integration on microbial community were studied in soil samples from five long-term fertilizer experiments under various rainfed production systems in the semi-arid tropics (SAT) of India. Microbial population counts were analyzed by dilution plating and were in turn compared with different parameters such as soil treatments, soil type, soil microbial biomass C, soil organic C, rainfall and soil pH. The counts were high in treatments where combinations of organic and inorganic fertilizers were applied compared to control. Vertisols showed larger organic carbon levels than Alfisols. Fungal population was higher in acidic soils and in treatments under continuous inorganic fertilization treatments whereas a high number of bacteria were found in integrated use of organic and inorganic fertilizers. At most of the locations soil organic C and microbial biomass C showed significant positive (p ≤ 0.05) correlation with microbial populations. Thus, results suggest that even under arid and semi-arid tropical conditions, regular addition of nutrients in an integrated manner could improve soil organic carbon and microbial population counts. For each production system, better carbon sequestration management practices were identified.     

Variation in protein and nitrate content of vegetative growth of winged beans

Abstract

The 68 winged bean (Psophocarpus tetragonolobus) accessions evaluated showed considerable variability In protein and nitrate % and vigor of second year vegetative growth. Protein content of vegetative growth ranged from 11 to 32% with a mean of 22%. Nitrate content ranged from 0.01 to 1.02%. The 3 Psophocarpus scandens accessions evaluated tended to have about the same protein %, lower nitrate % and greater vegetative growth than P. tetragonolobus.     

云南热区山地经济林培育的新思路

从生态系统管理和生态经济学的观点出发 ,提出了发展云南热区经济林产业应遵循的原则 ,应采取的树种及其品种选择、构建“乔灌草”结合的复层多种混交经济林、建立“种养加”相结合的高效产业链、建立中心苗圃和种质资源圃与试验示范地的技术措施 ,以及建立水资源管理与肥料支持系统、采取生物多样性保护和土壤肥力可持续利用的管理保护措施。以其新的思路供培育热区山地经济林参考     

A review of potato propagation by means of seed, as distinct from clonal propagation by tubers

Summary The vast majority of cultivated potatoes are vegetatively propagated, outbred autotretraploids. Disease problems dominate the maintenance of vegetative stocks. There have been recent proposals to propagate the crop by sexual seed in order to evade some of those disease problems. Some success has been achieved but controlled crosses are necessary to avoid inbreeding depression and seed propagation is not as cheap or simple as had been hoped. The idea has evoked wide interest throughout the tropics and has had some (and increasing) practical impact on China, India and Vietnam. There is a strong tendency to use ‘tuberlets’ borne on crowded nursery plants rather than to grow true seedlings. Some seedling families have looked locally attractive but it is not always realised that to use them implies the abandonment of about half the genetic variation, a heavy price to pay for disease avoidance. There is emerging recognition that vegetative and seed propagation are complementary rather than competitive and that good breeding programmes will therefore serve both. This review concentrates upon genetic/plant breeding aspects of propagation by seed, a subject hitherto largely neglected in the literature.     

The effects of alley cropping withLeucaena leucocephala and of different management practices on the productivity of maize and soil chemical properties in lowland coastal Kenya

The effects of leucaena hedgerows, mulching with leucaena foliage (0,50 and 100% of harvested foliage), cowpea intercropping and adition of dairy cattle slurry (55 t ha^–1 per maize crop) on the yield of maize from a sandy soil were assessed. The four-year results from five maize crops are reported.Except in the first year, yields of maize grain and stover were significantly reduced by 30% in the presence of leucaena hedgerows. Use of leucaena mulch eliminated this effect; application of all the harvested leucaena mulch (100%) increased the total maize grain yield of the five crops by 44% over sole maize. Hedgerow and mulching management required an additional 36 mandays labour ha^–1 which was more than compensated by the increased maize yields. Furthermore leucaena hedgerows substantially depressed the growth of weeds between cropping seasons.Intercropping with cowpea significantly depressed yields of maize grain and stover when both crops were sown together, but not in later seasons when cowpea was sown four weeks after the maize. Application of slurry increased the total yields of maize grain and stover by 35 and 37%, respectively. The grain yield of maize in leucaena hedgerow treatments fertilized with slurry did not respond to application of more than 50% of leucaena foliage, which suggested that half of the foliage could be spared for feeding to livestock. The cumulative yield of maize grain from the highest yielding organic system was 85% of the yield from the fertilizer treatment.The study, which is continuing, demonstrates that large increases in agricultural productivity are possible through the intercropping of maize with woody forage and grain legumes and the integration of dairy cattle production into the system. It thus shows the importance of exploiting crop/livestock interactions.