Rooting systems of western and southern African Faidherbia albida (Del.) A. Chev. (syn. Acacia albida Del.) —a comparative analysis with biogeographic implications

Faidherbia albida is a well-known and widespread agroforestry species of the Sudano-Sahelian zone of West Africa. Recent collection and testing efforts have included attempts to introduce seed origins from eastern and southern Africa into the Sahel. These have generally met with failure. Despite superior early growth, mortality is severe by the first or second year. Trials conducted at the ICRISAT Sahelian Center in Niger have demonstrated that this is probably due to differences in rooting patterns between southern and western Africa origins. A separation of the species into two ecotypes, i.e., upland (western Africa) and riparian (eastern, southern and southwestern Africa) is proposed. Based on this argument, the Sudan/Ethiopia region is identified as a possible center of origin for the species. Submitted as ICRISAT Journal Article # JA-1107.     

Woody legumes as live support systems in yam cultivation

This paper reports on the use of three leguminous perennials (Leucaena leucocephala, Flemingia macrophylla and Gliricidia sepium) as live support systems in yam cultivation. In a planting arrangement in which yam rows alternated with rows of the woody species the tuber yields per ha were 3.4 (leucaena), 5.3 (flemingia) and 10.1 (gliricidia) ton fresh weight. TUKEY's L.S.D. value equalled 2.9 ton. Leucaena leucocephala is unsuitable as live support since the species shows a strong competitive power expressed in terms of leaf productivity and relative density of the root mass in the upper soil stratum, the zone explored by the yam crop. Flemingia macrophylla is unsuitable as support species mainly because of its structural weakness: Its branches do not sufficiently lignify to carry the yam leaf mass. The significantly higher tuber yield of the yam crop grown with Gliricidia sepium is a function of specific properties of the tree species: Low leaf productivity, a relatively weakly developed root system and an open architecture, which leaves sufficient space for a yam crop grown in association.     

The espinal: agroforestry systems of the mediterranean — type climate region of Chile

The Central Valley of Chile is largely occupied by a pseudo-savanna called espinal consisting of a single dominant tree species, Acacia caven (Mol.) Mol. (Leguminosae), and some 215 annuals, most of which were inadvertently introduced from the Mediterranean Basin. The probable origin and current distribution of the espino (Acacia caven) and the espinales in Chile are described. Predominant production systems of the espinal in both the semiarid and subhumid regions of Chile are outlined, with emphasis on the later region. Causes of the current low levels of productivity are discussed, and various strategies for long-term improvement of the espinal are presented.     

Farmers preferences,uncertainties and opportunities in fruit-tree cultivation in Northeast Luzon

The world production of tropical fruit was estimated at about 65 Mt in 2002, of which developing countries accounted for 98%. Although most commercial fruit tree crops are cultivated by large-scale commercial enterprises, smallholder fruit-tree cultivation receives much attention in projects aimed at rural development, conservation farming and agroforestry in developing countries. In the Philippines, the integration of fruit trees in smallholder upland farming systems has been promoted since the 1970s. The aim of this paper is to investigate farmers’ views on small-scale fruit-tree cultivation based on fieldwork conducted in three upland villages of Northeast Luzon. The factors influencing farmers’ preferences are explored and the costs and benefits of fruit tree cultivation compared with those for seasonal cash crops over a 10-year period. Markets for fruit-tree products are identified, at both local and supra-local levels, and risks, uncertainties and opportunities associated with fruit-tree cultivation are discussed. Despite extensive promotion, the adoption of fruit trees in farming systems has occurred at a relatively low pace. In contrast, the cultivation of seasonal cash crops, particularly high-yielding rice and corn varieties, spread rapidly in the 1970s and 1980s. These crops are planted in monocultures with high inputs of fertilizers and pesticides. Farmers consider fruit trees as a subordinate crop much less profitable than seasonal cash crops, which is in stark contrast with the results of economic analyses of a 10-year production cycle. The Net Present Value (NPV) for citrus (Citrus reticulate) cultivation is at least two times the NPV for irrigated rice and as much as four times the NPV for corn, even at discount rates up to 20%. Farmers’ knowledge of tree management and species selection proved to be inadequate, contributing indirectly to low growth rates and fruit production. Marketing opportunities are not fully utilised as evident from unstable network channels for fruit-tree sales, lack of expertise in fruit-tree marketing and insufficient knowledge on market demands, quality production and market location.     

Cone and seed production from stone pine (<Emphasis Type="Italic">Pinus pinea</Emphasis> L.) stands in Central Range (Spain)

Natural regeneration of stone pine (Pinus pinea L.) stands in the Central Range of Spain can be difficult to attain. The success of this regeneration is affected by factors such as the total amount of seed available, the short dispersal ability of the pinyon, the conditions required for germination, specific problems associated with the establishment, early survival of the seedlings due to severe summer heat and drought, competition for water and mineral resources and grazing damage. This study focuses on seed availability. The amount of available seeds depends on the number and size of the cones and the number of viable pinyons within the cones. In stone pine stands, both variables show great year to year variability. Both cone and seed production, for a given year, are also conditioned by the vigour and health of the tree, its size, the condition and attributes of the stand and the loss of seed through pests or predation. In this study, the main factors which influence cone and pinyon production are identified and a multivariate model to predict annual cone and viable seed production is developed. To consider the correlation among observations coming from the same tree, stand or year, random components are included in the model. The multivariate random structure allows for future calibration of the model for a given year from a small additional sample of observations. It is important to know the total amount of viable seed produced in a stand for a given year since regeneration cuttings for Stone pine should be concentrated in high crop years.     

Profile Distribution of Carbon Fractions Under Long‐term Rice‐wheat and Maize‐wheat Production in Alfisols and Inceptisols of Northwest India

The knowledge of profile distribution of soil organic carbon (SOC) in long‐term agricultural systems could help to store atmospheric carbon in the soil. We investigated profile distribution of easily oxidisable Walkley–Black SOC pool (SOC_WB) under long‐term rice‐wheat (R‐W) and maize‐wheat (M‐W) cropping systems under soils of different pedogenesis. The soil samples were collected from the characteristic genetic horizons and analysed for carbon fractions. The SOC_WB was the highest in soils under R‐W systems in both Alfisols and Inceptisols. The SOC_WB stock in the deeper profile horizons under R‐W system was significantly (p < 0·05) higher than that under M‐W system especially in Typic Hapludalfs. Long‐term R‐W system could store on average 3·55 Mg ha⁻¹ more SOC_WB than M‐W system in the Ap horizon. The SOC_WB stock in the Ap horizon of all pedons was significantly (p < 0·05) higher in Alfisols than that in Inceptisols. About 60–90% of the total profile SOC_WB stock was contributed by B‐horizon because of its greater extent. Considering the whole profile, clay was negatively correlated with SOC fractions; however, the SOC fractions were closely related to each other. This study reveals that the distribution of SOC_WB is different in long‐term R‐W and M‐W systems not only in surface but also in the deeper horizons and the magnitude of the variation is influenced by the specific pedogenic processes. This indicates the significance of profile SOC_WB stock instead of topsoil SOC_WB stock in quantifying carbon retention potential of the long‐term management practices. Copyright © 2014 John Wiley & Sons, Ltd.     

盐碱地甜菜主要农艺措施数学模型

应用二次旋转设计，研究了大同盆地盐碱地甜菜覆膜和露地栽培中的５项主要因素。结果表明：（１）影响甜菜产量的因素重要性顺序为，施氮量＞施磷量＞密度＞微肥用量＞追肥比例。（２）密度与施氮量，施氮量与施磷量的因素配合对甜菜产量有明显的正的交互作用。（３）覆膜甜菜产量高于露地甜菜产量，但增加投肥量可部分地补偿两者的差异。（４）试验得到的产量函数模型，平均优化方案及不同产量水平的栽培方案可在类似生产条件下推广     

西藏自治区农牧民人均年收入发展趋势的 预测模型研究及应用

应用灰色系统理论并结合近几年的有关统计结果，对西藏自治区农牧民人均年收入建立了预测模型并进行了预测。计算结果表明，该预测模型具有较好的预测精度。     

防腐剂在烟熏火腿中的应用研究

通过正交试验发现,最佳的减菌剂组合为:乙酸2%,乳酸钠3%,VC1%,硫代硫酸钠4%,山梨酸钾1%。筛选了3种有效的防腐剂,并通过3因子二次通用旋转组合设计建立了防腐模型,所得回归方程能有效代表实际情况,最优组合为:Nisin0.038%,EDTA2.005%,乳酸钠2.843%。验证实验显示,组合防腐剂能有效抑制烟熏火腿中微生物的生长,使产品细菌总数不超过10000cfu/g,在温度0￣4℃条件下,烟熏火腿的贮藏期达21d以上,延长保质期10d以上。     

LOAD FREQUENCY CONTROL USING DECOMPOSED DISCRETE MODELS

Decomposed discrete models, can be used to design load frequency' controllers in multi-area power systems.Considering the exchanging real power in tie-lines as a measurable disturbance, the multi-area power system is decomposed into several subsystems.On the basis of generalized minimum variance control principles, an expanded control rule is induced. Using discrete models, the proposed method greatly decreases the number of varialles in be measured and simplifies the control system. The method is illustrated with a two-area power system example and its simulation Jesuits.