河南开封土壤养分变化特征及其持续利用途径研究

通过 1 984～ 1 998年河南开封不同土壤耕层有机质与氮磷钾养分分析 ,论述了不同农业利用方式和农田管理措施下不同土壤耕层养分的时空变化特征和硝态氮累积特性 .由于“重氮磷 ,轻有机肥 ,忽视钾素补给” ,土壤养分变化的总趋势以下降 ,钾素耗竭性明显 .土壤养分空间变化较为复杂 ,但不同土壤间耕层养分为普通淡色潮湿雏形土 >底锈干润雏形土 >石灰淡色潮湿雏形土 >灌淤旱耕人为土 >简育干润雏形土 >干润砂质新成土 .硝态氮累积表现为由上至下递减或由上至下递增和相对积累于土体某一深度 .最后研究提出了土壤持续利用的有效技术途径 .     

Soil morphological and chemical properties in homegardens on sandy beach ridges along the east coast of Peninsular Malaysia

The morphological and chemical properties of homegardens in the beach ridges with interspersed swales (BRIS) soils were evaluated in order to find a clue for developing sustainable agricultural management. Field survey and soil sampling were conducted at the homegardens and secondary forests in Sungai Ular Village and in the experimental farm of Malaysian Agriculture Research Institute (MARDI), Cherating Station. Chemical fertilizers including ash, charcoal waste and plant litter were applied to the homegardens in both the inland-ward area (HG-I) and in the shoreline area (HG-S). Manure was applied in HG-I and seafood waste from fish processing was buried in the soils in HG-S. High correlation was found between total carbon (T-C) and cation exchange capacity (CEC), indicating soil organic matter was the determinant factor for CEC in the very sandy BRIS soils. The levels of T-C, total nitrogen (T-N), and CEC at 0–10 cm in HG-I in parallel with increasing ages of homegardens. The soils in 0–10 cm and 20–30 cm showed higher levels of T-C and T-N with higher C/N ratios in HG-I than in HG-S and the MARDI farm. The high levels of exchangeable Ca, Mg, and K in HG-I compared with the MARDI farm, suggesting that improved CEC with increasing soil organic matter in HG-I heighten the retention of basic cations supplied as chemical fertilizer, ash, and manure. The level of available P was higher in HG-S than HG-I, attributed by the seafood waste application in the shoreline area. Thus, on the BRIS, the levels of soil organic matter and nutrients can be sustained by the homegarden management although it cannot be regarded as a closed system compared with those in the other tropical regions because chemical fertilizer was used and a certain amounts of nutrients seemed to leach down beyond plant rooting depth.     

塔里木盆地潮湿冲积新成土形成特点

干旱内陆地区的潮湿冲积新成土主要位于大河两岸的河滩地,它的地下水位高,土壤水分为潮湿状态。受到洪水的影响,虽然盐分已具有表聚,但缺乏盐结皮层。由于不断有新的泥沙沉积物加入,土壤无明显发育,而且其性状受土壤质量地影响。     

Soil Degradation and Soil Productivity Restoration and Maintenance in Hilly Land of Southern China

Soil fertility degeneration and land productivity loss caused by soil erosion are severe problems in hilly land of southern China. A long term field experiment was conducted during 1984 to 1993 to determine soil productivity in a typical degraded hilly area of purple soil (orthic Entisol) in Yanting, Sichuan, China. Results showed that a conservation tillage system with ridge-furrow cropping and seasonal no-tillage increased topsoil depth by 118 mm over the conventional tillage. Soil structure and soil physical, chemical and biological characteristics were also improved when conservation tillage was adopted. In conclusion, this system is suitable conserving soil and water resources and therefore for restoring dry land crop production in degraded hilly land of southern China     

SEASONAL NITROGEN BUDGETS OF MATURE CITRUS TREES ON A SANDY ENTISOL

Approximately 30% of Florida citrus is grown on well-drained Entisols with low nutrient-holding capacity, which are prone to high nitrogen (N) leaching losses. However, increasing application frequency of N-fertilizer via multiple fertigations does not increase crop yield, whereas in agronomic crops, such an approach typically enhances N uptake efficiency. We assessed seasonal tree N tissue concentration dynamics as affected by N rate for mature fourteen-year-old ‘Hamlin’ orange (Citrus sinensis L. Osbeck) trees on either Carrizo citrange (C. sinsensis L. Osbeck X Poncirus trifoliata L. Raf.) or Swingle citrumelo (C. paradisi Macf. X P. trifoliata L. Raf.) rootstocks. Nitrogen was applied as ammonium nitrate in six split fertigation applications with N target values of 179 and 269 kg ha^?1yr^?1. Leaf, twig, and branch bark tissue N concentrations decreased through the spring to minima in May and June. This time period corresponds to a period of high N demand associated with both vegetative and reproductive growth. Tissue N concentrations increased from late spring minimums to fall and winter maximum concentrations. Reduction in branch bark and wood tissue N concentrations may have been due to a redistribution of N to leaf, twig, and fruit tissues in response to low N supply. The majority of the spring N should be supplied prior to May.     

Root biomass and distribution of a <Emphasis Type="Italic">Picea–Abies</Emphasis> stand and a <Emphasis Type="Italic">Larix–Betula</Emphasis> stand in pumiceous Entisols in Japan

Root biomass and root distribution were studied in Entisols derived from the thick deposition of volcanic pumice on Hokkaido Island, Japan, to examine the effect of soil conditions on tree root development. The soil had a thin (<10 cm) A horizon and thick coarse pumiceous gravel layers with low levels of available nutrients and water. Two stands were studied: a Picea glehnii–Abies sachalinensis stand (PA stand) and a Larix kaempferi–Betula platyphylla var. japonica stand (LB stand). The allometric relationships between diameter at breast height (DBH) and aboveground and belowground biomass of these species were obtained to estimate stand biomass. The belowground biomass was small: 30.6 Mg ha₋₁ for the PA stand and 24.3 Mg ha₋₁ for the LB stand. The trunk/root ratios of study stands were 4.8 for the PA stand and 4.3 for the LB stand, which were higher than those from previous studies in boreal and temperate forests. All species developed shallow root systems, and fine roots were spread densely in the shallow A horizon, suggesting that physical obstruction by the pumiceous layers and their low levels of available water and nutrients restricted downward root elongation. The high trunk/root ratios of the trees may also have resulted from the limited available rooting space in the study sites.     

Distribution of inorganic phosphorus fractions in some soil profiles of Zagros forest of Iran

The aim of the present study was to evaluate the status of inorganic phosphorus (P) fractions in ten virgin soil profiles, and to study the relationships between P fractions and soil properties from Kohgyloyeh and Boir Ahmad province, Iran. The soils belonged to Alfisols, Entisols, Mollisols, and Inceptisols. Mean annual precipitation and temperature ranges were 450–850 mm and 12.2–22.4°C, respectively. Inorganic P was fractionated by sequential extraction with NaHCO₃, NH₄OAc, MgCl₂, NH₄F, NaOH, citrate-dithionite-bicarbonate (CBD), and H₂SO₄, which are referred to as NaHCO₃–P, NH₄OAc–P, MgCl₂–P, NH₄F–P, NaOH–P, CBD–P, and H₂SO₄–P, respectively. Generally, the NaHCO₃–P, NH₄OAc–P, MgCl₂–P, and NH₄F–P were higher in surface horizons, especially wherever there was higher annual precipitation. Results showed that H₂SO₄–P constituted the largest inorganic P fractions in all profiles. For all the soils studied the distribution of P fractions was similar to that of weakly weathered soils under arid and semi-arid regions which represent an early stage of development. Pedogenic P compounds were higher where weathering was higher, i.e., in surface horizons and at higher annual precipitation.     

Effects of sowing date, tillage and residue management on productivity of cotton (Gossypium hirsutum L.)–wheat (Triticum aestivum L.) system in northwest India

In southwestern region of Punjab in north India, sowing dates of cotton crop in cotton (Gossypium hirsutum L.)–wheat (Triticum aestivum L.) system are staggered from last week of April to mid of May depending upon the surface water supply from canal as ground water is not fit for irrigation. Further, farmers practice intensive cultivation for seedbed preparation and burning of wheat straw before sowing of cotton crop. With the present farmers’ practices, yields have become static and system has become non-profitable. Field experiments were conducted on Entisols for two rotations of cotton–wheat system during the years of 2004–2005 and 2005–2006 in split plot design to study the direct and interactive effects of date of sowing and tillage-plus-wheat residue management practices on growth and yield of cotton and wheat and to increase the profitability by reducing the tillage operations, which costs about 50% of the sowing cost. The pooled analysis showed that in cotton crop, there was a significant interaction between year × dates of sowing. Among different tillage-plus-wheat residue management practices yields were 23–39% higher in tillage treatments than minimum-tillage. In wheat, grain yield in tillage treatments were at par. Water productivity amongst the tillage treatments in cotton was 19–27% less in minimum tillage than others tillage treatments. Similar trend was found in wheat crop. Remunerability of the cotton–wheat system was more with a combination of reduced tillage in cotton and minimum tillage in wheat than conventional tillage.