Productivity of single-culm and multi-culm plants of winter wheat cultivars in field conditions

Summary The productivity of 1-, 2-, and 3-culm plants of three winter wheat cultivars was studied under field conditions in three spatial arrangements. The treatments with 2- and 3-culm plants produced higher grain yield per unit area than the treatments with 1-culm plants. This was explained as the result of a higher interplant than intraplant competition. It seems that the interplant competition is lower with dwarf than with tall cultivars. The secondary culms may be as productive as the primary ones if there are only a few of them per plant and if they develop before the beginning of winter. If the tillering takes place mainly in spring, the differences in productivity between the primary and secondary culms are considerable. Under conditions of dry autumns and late planting not the tillering must be taken as the main factor which regulates the optimal number of spikes/m², but the high planting rate.     

An estimation of homogeneity in crop plants,with special reference to genetic vulnerability in the dry bean,Phaseolus vulgaris L.

Summary A general method of quantitatively assessing genetic similarity among a set of cultivars of a given crop is proposed, and its application to dry beans in the United States is demonstrated. The method is based upon the multi-variate technique of Principal Components Analysis. Using this method it was possible to calculate a distance metric between any two cultivars in the set and to show that such distances were highly inversely correlated with genetic relationship estimated from a knowledge of breeding ancestry.On the basis of distances among cultivars within given production regions (states in the US in this case) and knowledge of the acres of each cultivar grown in the region, an average weighted distance metric appropriate to each was calculated. Each derived distance metric serves as an index of genetic homogeneity for the crop in that region. Arguments are presented for relating the degree of vulnerability to a disease epidemic to the distance index. Indexes are calculated for nine of the major bean producing states in the US from which it is concluded that, from the standpoint of genetic vulnerability, Colorado is most vulnerable and California least vulnerable to a region-wide epidemic affecting the bean crop. It is suggested that the method demonstrated here is of nearly universal applicability, and particularly meaningful with respect to self-fertilizing crops.     

A comparison of apple and pear seedlings with reference to the juvenile period I. Seedling growth and yield

Summary Several thousand apple and pear seedlings of many progenies were studied in connection with their juvenile period (J.P.). The initially significant inverse relation between the vigour (stem diameter) and the J.P. of the seedlings became insignificant as the trees grew older, due to a retardation of growth occurring when the seedlings become generative. This relation can be used effectively in pre-selecting for vigour in the nursery. Cumulative yields were higher when the J.P. was shorter, but there was no evident link between the J.P. and annual yield in full bearing, that is to say, precocity and preductivity are not directly connected. Better growing conditions and pre-selection have shortened the mean progeny J.P. of either crop by three years since the 1950's. Generally, the pear seedlings appear to grow faster, to become generative slower and to yield lower than comparable apple seedlings. The mean J.P. of apple and pear progenies averaged 4.2 and 6.0 years respectively. The difference between apple and pear may be attributable to a greater selection pressure on both precocity and productivity with apple than with pear.This possibly also led to a smaller tree in the productive phase on the assumption that tree size at first flowering-small at a short, large at a long J.P.-expresses reproductive efficiency and as such is reflected in the size of the adult tree.Also presented at the Juvenility Symposium held at West-Berlin, November 1976.     

Intragenic vectors for gene transfer without foreign DNA

The intragenic vector system involves identifying functional equivalents of vector components from the genome of a specific crop species (or related species to which it can be hybridised) and using these DNA sequences to assemble vectors for transformation of that plant species. This system offers an attractive alternative to current genetic engineering strategies where vectors are based on DNA sequences that usually originate from bacteria. The construction of intragenic vectors enables the well-defined genetic improvement of plants with all transferred DNA originating from within the gene pool already available to plant breeders. In this manner genes can be introgressed into elite cultivars in a single step without linkage drag and without the incorporation of foreign DNA. The resulting plants are non-transgenic, although they are derived using the tools of molecular biology and plant transformation. The use of intragenic vectors for the transfer of genes from within the gene pools of crops may help to alleviate some of the major public concerns over the deployment of GM crops in agriculture, notably the ethical issue associated with the transfer of DNA across wide taxonomic boundaries. This paper reviews the progress toward the development and use of intragenic vectors and the implications of their use for the genetic improvement of crops. Dedicated to the late Hans Sandbrink for his enthusiasm in helping to develop intragenic vectors     

The Impact of Underground Longwall Mining on Prime Agricultural Land: A Review and Research Agenda

Coal mining and agriculture have repeatedly come into conflict when they co‐occur. Although seemingly benign when compared with surface mining, underground coal extraction techniques (including longwall mining) cause subsidence of agricultural land and loss of productivity. Despite growing concerns for global food security and increasing demand for coal resources, there is little peer‐reviewed literature on the impacts of longwall mining in prime agricultural areas. In this paper, we examined the present knowledge of subsidence impacts of longwall mining on agriculture and how this may be interpreted for specific locations such as Australia. The review found that subsidence affects soil properties, hydrology and topography. The main impacts on agriculture are altered soil and groundwater hydrology, modified topography associated with increased erosion or waterlogging risk, and zones of compaction or cracking that cause soil physical and chemical changes. Agricultural productivity is also reduced through altering the types of farming practices that are suited to subsided non‐uniform landscapes, decreasing farming efficiency through increasing paddock heterogeneity and decreasing ease of workability. There is a need to consider these multiple impacts under local conditions, with particular regard to the interaction of mine subsidence‐associated disturbances with farming practices. We conclude by describing future research directions required for Australia and other countries outside of the USA—where most of the research has been conducted. Australia has unique soil and climatic conditions making extrapolation of studies from the USA on subsidence impacts and mitigation problematic. Copyright © 2014 John Wiley & Sons, Ltd.     

柳杉人工林生物量及生产力研究

对广西六万林场31年生柳杉人工林的生物量和生产力进行研究,并建立柳杉不同器官的生物量模型。结果表明:不同径阶单株平均木生物量随着径阶的增大而增大,且不同径阶间生物量差异显著;所拟合的各器官生物量的回归估测模型的决定系数R2值均在0.983以上,达0.01显著水平;不同器官生物量大小依次为:树干>枝条>根蔸>树叶>枯枝>粗根>细根>中根;林分乔木层总生物量达到了239.03 t.hm-2,其中树干的生物量达到了120.24 t.hm-2,占全株的50.30%;林分的年净生产力达7.89 t.hm-2.a-1。     

河南省林业企业全要素生产率的测定

河南省林业企业主要分布于第一产业、第二产业,利用生产函数和索洛增长速度方程法来测算科技对林业企业贡献大小。经测算,河南省林业企业2000-2004年平均全要素生产率为11.74%。科技对河南省林业企业发展贡献较低。     

我国人工林地力衰退与维护研究

本文从育林措施、气候、土壤、人工林群落结构、树种等方面概述了引起地力衰退的主要因素和应对策略。     

油茶林分生物量及生产力的研究

本文对３种不同产量水平的油茶林分生物量和生产力进行了测定和研究。结果表明：产油水平从高到低编号为Ⅲ、Ⅱ、Ⅰ的样地，其林分总生物量分别为７５．７１、４１．５５、３０．４９ｔ／ｈｍ＾２，年平均净生产量分别是５．４９、３．１２、１．１７ｔ／ｈｍ＾２。各样地油茶林分各组分生物量所占比例的排序为干〉根〉枝〉叶〉果〉花。各组分枝叶比，果叶比、非光合与光合部分比值均为Ⅲ号样地最大。     

Sloping Agricultural Land Technology (SALT): a sustainable agroforestry scheme for the uplands

Soil erosion due to deforestation and heavy rains presents an extremely serious problem in many parts of Southeast Asia, particularly in the upland Philippines. The Mindanao Baptist Rural Life Center (MBRLC), a non-government organization based in the southern part, has developed and spread an agroforestry scheme called Sloping Agricultural Land Technology (SALT) to help control soil erosion and increase crop yields. Basically, SALT utilizes nitrogen-fixing trees as soil binder, fertilizer generator, and livestock feed source. The system also includes annual and perennial diversified food crops grown in the spaces between the hedgerows. The SALT model has been tested both in demonstration plots and farmers' fields, and has proven to be appropriate for use by typical hilly-land farmers. The system can reduce soil erosion and restore moderately degraded hilly lands to a profitable farming system.