Soil organic carbon sequestration as affected by tillage, crop residue, and nitrogen application in rice–wheat rotation system

Despite being a major domain of global food supply, rice?Cwheat cropping system is questioned for its contribution to carbon flux. Enhancing the organic carbon pool in this system is therefore necessary to reduce environmental degradation and maintain agricultural productivity. A field experiment (November 2002?CMarch 2006) evaluated the effects of soil management practices such as tillage, crop residue, and timing of nitrogen (N) application on soil organic carbon (SOC) sequestration in the lowland of Chitwan Valley of Nepal. Rice (Oryza sativa L.) and wheat (Triticum aestivum L.) were grown in rotation adding 12?Mg?ha^?1?y^?1 of field-dried residue. Mung-bean (Vigna radiata L.) was grown as a cover crop between the wheat and the rice. Timing of N application based on leaf color chart method was compared with recommended method of N application. At the end of the experiment SOC sequestration was quantified for five depths within 50?cm of soil profile. The difference in SOC sequestration between methods of N application was not apparent. However, soils sequestered significantly higher amount of SOC in the whole profile (0?C50?cm soil depth) with more pronounced effect seen at 0?C15?cm soil depth under no-tillage as compared with the SOC under conventional tillage. Crop residues added to no-tillage soils outperformed other treatment interactions. It is concluded that a rice?Cwheat system would serve as a greater sink of organic carbon with residue application under no-tillage system than with or without residue application when compared to the conventional tillage system in this condition.     

Pea–barley intercropping for efficient symbiotic N2-fixation,soil N acquisition and use of other nutrients in European organic cropping systems

Complementarity in acquisition of nitrogen (N) from soil and N₂-fixation within pea and barley intercrops was studied in organic field experiments across Western Europe (Denmark, United Kingdom, France, Germany and Italy). Spring pea and barley were sown either as sole crops, at the recommended plant density (P100 and B100, respectively) or in replacement (P50B50) or additive (P100B50) intercropping designs, in each of three cropping seasons (2003–2005). Irrespective of site and intercrop design, Land Equivalent Ratios (LER) between 1.4 at flowering and 1.3 at maturity showed that total N recovery was greater in the pea–barley intercrops than in the sole crops suggesting a high degree of complementarity over a wide range of growing conditions. Complementarity was partly attributed to greater soil mineral N acquisition by barley, forcing pea to rely more on N₂-fixation. At all sites the proportion of total aboveground pea N that was derived from N₂-fixation was greater when intercropped with barley than when grown as a sole crop. No consistent differences were found between the two intercropping designs. Simultaneously, the accumulation of phosphorous (P), potassium (K) and sulphur (S) in Danish and German experiments was 20% higher in the intercrop (P50B50) than in the respective sole crops, possibly influencing general crop yields and thereby competitive ability for other resources. Comparing all sites and seasons, the benefits of organic pea–barley intercropping for N acquisition were highly resilient. It is concluded that pea–barley intercropping is a relevant cropping strategy to adopt when trying to optimize N₂-fixation inputs to the cropping system.     

Effects of organic amendment and water regime on methane emission from rice fields

To evaluate the effects of irrigation and organ-ic matter on methane emission,experimentswere conducted on Aqu-paddy soil with pH6.2,24.16g·kg~(-1) of organic C,2.2g·kg~(-1)of total N,14.4 C mol·kg~(-1) of ECE,53%silt,and 43% clay on CNRRI farm.The plotarea was 5m×5m,and the experiment wasdesigned in a completely randomized block de-sign with 4 treatments and 3 replications.Thefour treatments were:local practice withoutgreen manure (T_1),intermittent irrigation(T_2),applying inorganic fertilizer with greenmanure and local practice irrigation (T_3,con-trol),and continuous irrigation(T_4).     

Are there alternatives to copper for controlling grapevine downy mildew in organic viticulture?

Downy mildew caused by the obligate biotrophic oomycete Plasmopara viticola is one of the most important and devastating diseases of grapevine. Copper-based fungicides are used to control the disease in organic vineyards. However, since 2006, copper use has been limited by an European Commission regulation. In this study conducted from 2004 to 2007, we tested materials that might replace copper in organic viticulture, under controlled greenhouse and field conditions at two locations in Europe (northern Italy and Switzerland). We tested 112 different treatments, including biocontrol agents, materials of animal origin, homeopathic preparations, inorganic materials, microbial extracts, natural derivatives, plant extracts, physical methods and synthetic materials. Good control results were observed for two new copper formulations, but one of them induced phytotoxic effects. Two of the plant extracts provided good control on both leaves and clusters, and six of them controlled the infection on clusters only. One biocontrol agent reduced symptoms on leaves and bunches. Three of the other treatments provided good control on leaves, and four of them provided good control on bunches. Clay was as effective as copper on both leaves and bunches. Currently, even if there is no treatment that is as effective as copper for controlling grapevine downy mildew in organic vineyards, Yucca schidigera and Salvia officinalis extracts and Trichoderma harzianum, could be considered as promising candidates to be developed. This study may help the development of an integrated management program in which a less effective product is applied in combination with copper, to reduce the total quantities of copper applied.     

Fermented Milk–Starch and Milk–Inulin Products as Vehicles for Lactic Acid Bacteria

Formulations using cassava starch or inulin plus milk were fermented with three different lactic acid bacteria (LAB) strains: Lactobacillus plantarum D34, Lactobacillus sp. SLH6, and Streptococcus thermophilus ST4. Growth and acidification were followed in 3% powdered milk (M3), 3% milk–6% starch (M3-S6), and 3% milk–6% inulin (M3-In6). D34 and SLH6 growth was enhanced by starch in M3-S6, when compared to the count (CFU/ml) obtained in M3. Growth of all strains was promoted by inulin. All fermented products showed LAB counts of 8.0 log or higher. Carbohydrate utilization was in agreement with growth and acidification results. The highest increase in CFU in rat feces was observed in M3-S6 fermented with ST4; the D34 fermented product also increased CFU but SLH6 did not, either with starch or inulin. This suggests that ST4 and D34 strains provide a good choice to ferment the proposed formulations in order to obtain a marked improvement of natural intestinal flora.     

Presence of β-glucanase activity in wheat and dairy ingredients and use of organic salts as potential enzyme inhibitors

Depolymerization of mixed linkage cereal β-glucans has been observed during the mixing and fermentation of multigrain breads. To maintain the bioactivity of β-glucans in bread and other foods, control of β-glucanase activity during production is needed. β-Glucanase activity in wheat and dairy ingredients was determined by adding them to β-glucan solutions and following the change in the molecular weight of β-glucan at 50 °C for 60 min. The activities in six wheat and six dairy ingredients ranged from undetectable to a 98% reduction in molecular weight. Calcium propionate, potassium sorbate, and sodium benzoate are salts of organic acids commonly used as food preservatives. Low concentrations of these additives (0.1–1.0%) were found to have an inhibitory effect on the β-glucanases found in wheat flour and whey protein isolate. The depolymerization rate of β-glucan was reduced by up to 76% by the three additives.     

Ring rot survey, 1940–1951

American Journal of Potato Research -     

Potato Crop Nitrogen Status Assessment to Improve N Fertilization Management and Efficiency: Past–Present–Future

Improving nitrogen use efficiency is important for the potato crop, because of its relatively low ability to take up available soil mineral nitrogen (N). Splitting of N fertilizer application is a suitable approach to better match N need and supply. In-season crop N monitoring methods are therefore required to support such strategies. This paper deals with the state of the art and potential development of characteristics, use and implementation of well known and more recent methods aimed to assess in-season potato Crop Nitrogen Status (CNS). A short overview of this concept is given for the potato crop. The most important and available methods for CNS assessment are evaluated for their accuracy, precision, sensitivity, sensibility and feasibility. These are: the petiole sap nitrate concentration test; the leaf chlorophyll concentration measurement using a hand-held chlorophyll meter; the measurement of crop light reflectance through a hand-held radiometer using passive sensors. More recent methods still under investigation based on near, ground-based, air-borne or space-borne remote sensing are discussed for their scientific and practical interest in the near future. The current and potential use and implementation of these methods into decision support systems for potato N fertilization management aimed at improving the potato crop nitrogen use efficiency are analysed by: comparing relative and raw data; establishing threshold values of CNS; and combining or integrating the CNS values into models dedicated to N recommendation or to crop growth simulation.     

Trends in rice–wheat area in China

This paper provides new estimates of area planted to the rice (Oryza sativa L.)–wheat (Triticum aestivum L.) rotation in China by combining the results obtained from two methodologies. One methodology uses official statistics at the province-level for sown area of rice and wheat, which allows construction of annual estimates from 1979 to 2001. The other methodology uses remote sensing data and county level Agricultural Census data on sown area of 17 major crops, which allows for construction of one estimate appropriate for the middle of the 1990s. The first methodology suggests that the area planted to the rice–wheat rotation has declined sharply in recent years. A combination of the two methodologies results in an estimate of rice–wheat area in China in 2001 of 3.4 Mha. This is substantially below other figures in the literature that reach as high as 13 Mha. This estimate, and the reasons for its declining trend over time, is important for setting priorities in crop research and for understanding how farmers might react to possible new productivity-enhancing technologies.     

Report of the Editors over 1996–1998

Reports

Report of the Editors over 1996–1998