Changes in Soil Properties under Two Different Management Systems in the Western Amazon

Upland soils in the Amazon basin are often highly weathered and therefore possess low plant-available nutrient contents. Soil fertility is principally maintained by geochemical, biochemical, and biogeochemical processes. Within these processes, the soil microbial biomass is responsible for many of the cycles and transformations of nutrients in soils. The aim of this work was to evaluate the changes in soil fertility, in the form of nitrogen (N) and microbial activity, as indicators of the dynamic of carbon (C) with two extractants [irradiation extraction (IE) and IRGA methods], N, and phosphorus (P) in an upland soil area containing a dystrophic Yellow Latosol (Xanthic Ferralsol) in the western Amazon (Brazil) with succession of two plant covers (citrus or pasture) and management. The study was carried out in two chronosequences: primary forest followed by citrus plantations and primary forest followed by pasture. The results showed that pasture has greater capacity to accumulate organic C and total N than either primary forest or citrus plantation. Removing forest to introduce pasture or citrus plantations influences the soil fertility and microbial biomass of C, N, and P in the soil. Under the edaphoclimatic conditions, the irradiation extraction and IRGA methods all proved efficient in determining the soil microbial C activity. In addition, regardless of the depth of soil, the predominant N form is ammonium (NH₄ ⁺).     

Straw coverage alleviates seasonal variability of the topsoil microbial biomass and activity

Straw coverage on soil surface is a well-known practice for conserving soil and water. Seasonal variability of microbial biomass carbon (MBC) and basal respiration (BR) in surface soil (0–5 cm) was compared between conventional straw removal (SR) and straw coverage (SC) in a maize (Zea mays L.) field experiment, Northeast China. The straw coverage treatment significantly increased microbial energy, carbon and nutrient sources (soil C and N contents) and improved soil physical environment (moisture and porosity), and thus stimulated MBC and BR across the growth season of maize, as compared to the straw removal treatment. MBC and BR showed similar seasonal trends in soil temperature, with maximum values in summer. In both study years, the straw coverage treatment reduced seasonal variation of soil temperature, therefore it significantly moderated seasonal variability of MBC and BR. Our results demonstrate that straw coverage contributes to stabilizing soil microbial characteristics in season.     

低湿耕地玉米分层配比施肥的研究

试验结果表明,玉米分层配比施肥,完全可以代替玉米种肥、追肥相结合施肥法,增产效果明显。特别是N、P、K全肥分层配比施用好于N、P肥分层配比施用,在低湿地有推广价值。     

Evaluation of pentoxifylline and Basal Medium Eagle supplemented to diluent on cryopreserved goat spermatozoa

This study investigated the effect of pentoxifylline (PTX) and Basal Medium Eagle (BME) on frozen–thawed goat spermatozoa. Immediately after initial examination of ejaculated semen, samples were pooled and reexamined for quality. Then, samples were divided into eight equal aliquots and diluted with a basic tris-extender containing PTX (3, 6, 9 mM) and BME (5 mM) to reach a final concentration of 25 × 10⁹ and frozen. After 24 hr, the samples were individually thawed at 37°C for 30 s and evaluated for different characteristics. Obtained post-thaw results from Computer-Assisted Sperm Analysis indicate using of 3 and 6 mM PTX led significantly to an improvement in total motility, progressive motility and velocity characteristics of spermatozoa, except the beat/cross frequency (BCF) which indicated statistically no differences (p > .05) among control and treatments. Diluents prepared with BME (5 mM) and PTX alone (3 and 6 mM) improved significantly the membrane integrity–functionality, acrosome integrity and also hyaluronidase activity. Regarding recovery rate, the results showed significantly (p < .05) higher values for diluents containing 3 and 6 mM PTX compared to other groups. Malondialdehyde concentration exhibited also a significant difference (p < .05) in diluents supplemented with 5 mM BME, 3, 6 and 9 mM PTX, and mixture of 3 mM PTX and 5 mM BME which illustrate a similarity for active mitochondria, apoptotic-like and dead spermatozoa. Finally, the ratio of sperm chromatin dispersion stained spermatozoa presented significant differences (p < .05) among treatments in which the diluents added PTX alone demonstrated significantly lower values than control and extenders containing the mixtures of BME and PTX. In conclusion, the observation in this study indicates using of 3 and 6 mM PTX and BME alone may improve significantly (p < .05) the quality of cryopreserved goat spermatozoa.     

四季萝卜追肥数量研究

本研究运用三元二次旋转回归设计进行四季萝卜（ＲａｐｈａｎｕｓｓａｔｉｖｕｓＬ．ｖａｒ．ｒａｄｉｃｕｌｕｓ）的追肥研究。研究结果表明：在低肥力地块上种植四季萝卜，追肥对产量形成有重要作用．氮、磷、钾单独施用均有提高产量的作用，配合施用时，它们彼此间对产量形成有交互作用．氮肥施用过量，不利于磷、钾增产作用发挥，增施磷肥，对氮的增产作用有所促进。为获得较好的产量，追肥适宜的用量分别是Ｎ４９４．７０ｋｇ／ｈｍ２，Ｐ２Ｏ５３１１．８５ｋｇ／ｈｍ２，Ｋ２Ｏ３１７．４０ｋｇ／ｈｍ２。     

Effect of nitrogen application during ripening period on photosynthesis and dry matter production and its impact on yield and yield components of semidwarf iniica rice varieties under water culture conditions

Abstract

A water culture pot experiment was conducted to analyze the effects of N application during the ripening period (RP) on photosynthesis, dry matter production, and its impact on grain ripening and yield in two semidwarf indica type varieties viz. Gui Zhao 2 (GZ) and BR3 (BR) compared with a japonica type variety Koganemasari (KO) under four N rates viz. 0 (N₀), 10 (N₁₀), 20 (N₂₀), and 40 (N₄₀) mg L^?1. Results showed that N application enabled to maintain a higher leaf area and delay leaf senescence in both indica and japonica type varieties but the decrease in the rate, of leaf area was higher in the former than in the latter and the rate was reduced with increasing N rates. Flag leaf photosynthesis and SPAD values of N treated plants were higher throughout the RP, showing the presence of a significant correlation either for each variety or all the varieties together. Higher photosynthetic rate was supported by higher leaf chlorophyll (SPAD value basis) content, stomatai conductance, and N concentration in leaf blades. Top dry matter content increased with increasing N rates mainly due to mean leaf area rather than NAR except for BR during RP but it was higher in KO than in GZ and BR. Reduction of shoot weight due to translocation of dry matter to panicles during RP was suppressed by N rates both in GZ and BR while shoot weight increased in the N-treated plants in KO. The dependency of KO on current photosynthates for panicle weight was found to be almost hundred percent while the contribution of stored carbohydrates in shoot before heading to panicle weight in GZ and BR was in the range of 4-27 and 33-54%, respectively and the rest was contributed by current photosynthates. The percentage increased with increasing N rates. Percentage of ripened grains (PRG) increased with increasing N rates in GZ and BR due to the increase in dry matter production and in the photosynthetic rates of apex leaves, despite the larger spikelet number and larger hull size. However, KO showed almost no variation although it had the highest PRG among the varieties. Brown rice yield followed the same pattern as that of PRG in GZ and BR and the highest yield was produced by BR followed by GZ and KO. These results suggest that N application during RP was more effective in increasing yield in the semidwarf indica type varieties than in the japonica type variety.     

Growth and yield studies of potato development in a semi-arid region. 3. Effect of water stress and amounts of nitrogen top dressing on physiological indices and on tuber yield and quality of several cultivars

Summary The response of five potato cultivars (Alpha, Cardinal, Désirée, Spunta and Up-to-Date) to a range of amounts of irrigation nitrogen top dressing (N.t.) in a rainless region was studied by means of the line-source sprinkler method. The irrigation-to-evaporation ratio,K _p, ranged from 0.14 to 1.27 and N.t. from 12 kg/ha to 201 kg/ha, respectively. In all cultivars, the yield increased linearly up toK _p=1.0; at higher ratios there was a yield decline in all cultivars except for Cardinal, in which the yield function flattened off. Spunta was the highest yielding cultivar (16t/ha) in the dry range (K _p=0.14; N.t.=12 kg/ha). Désirée was the highest yielding cultivar (64 t/ha) in the wet range (K _p=1.0; N.t.=201 kg/ha), and Alpha was the lowest yielding cultivar in both the dry and wet range (9 and 46 t/ha, respectively). Leaf permeability, leaf water potential and photosynthesis rate decreased, and tuber dry matter percentage increased with decreasingK _p: these indices also varied with plant age, and among cultivars. Yields were adversely affected when soil water potential at the 30-cm depth dropped below −0.4 bar. Contributon from the Agricultural Research Organization, The Volcani Center, Bet Dagan, Israel. No E-811, 1983 Series.     

糖厂酒精废液作追肥对甘蔗生长及产量的影响

以糖厂酒精废液为追肥(淋施)在甘蔗上进行了施用试验。结果表明,酒精废液在甘蔗生产上作早期追肥对甘蔗的分蘖、生长和提高甘蔗产量有明显的效果。以每667 m2施酒精废液4 t加尿素20 kg和施酒精废液3 t加尿素20 kg效果较好,理论产量分别达6 279.4 kg/667m2和6 065.3 kg/667m2,从节约生产成本和劳动力的角度出发,推荐施酒精废液3 t加尿素20 kg作追肥。     

吡虫啉拌种控制全生育期小麦蚜虫有效剂量评价

本文对吡虫啉拌种控制全生育期小麦蚜虫有效剂量进行了研究。结果表明,仅用吡虫啉拌种就可在小麦整个生育期将小麦蚜虫控制在防治指标之下,表现出超高效、持效的控制效果。1 kg种子用1.0~4.8 g吡虫啉（有效成分）拌种,从播种至灌浆末期,防治效果在95%以上,至乳熟期（收获期）防治效果仍高达74.49%~96.61%;千粒重比未拌种区增加了26.51%~36.55%。综合以上试验结果,吡虫啉拌种控制全生育期小麦蚜虫的经济、有效剂量为有效成分1.0~2.0 g/kg种子,最佳剂量为1.5 g/kg种子。     

Rain forest recovery from dieback,Queensland, Australia

We present a detailed account of a dieback episode in tropical rain forest. The dieback episode took place from 1977 to 1989 within a 0.5 ha long-term demography plot monitored for stem growth and mortality from 1975 to 2005. In total 770 m² of rain forest was affected causing 13 trees >10 cm diameter at breast height (dbh) to die, and others to sicken. The dead trees came from four families, though 14 families were represented in the area. Trees of the family Elaeocarpaceae suffered significantly higher mortality. Larger trees were significantly more likely to die than small trees, but smaller trees were more likely to recover. Recruitment to >10 cm dbh size class after dieback was greater in areas that had been affected, and in 2005 stem density and basal area were higher than in 1977, before the dieback episode started. There were no significant trends in biodiversity change between affected and non-affected parts of the plot. Dieback may have dramatic effects at onset but over the medium term its impact appears to be less serious. Longer term monitoring will permit re-evaluation of this observation in the future.