Crop & Pasture Science 

About: Crop & Pasture Science is an academic journal published by CSIRO Publishing. The journal publishes majorly in the area(s): Plant nutrition & Population. It has an ISSN identifier of 1836-0947. Over the lifetime, 7363 publications have been published receiving 217193 citations. The journal is also known as: agricultural crop & agricultural crops.

The analysis of adaptation in a plant-breeding programme

Abstract: The adaptation of barley varieties was studied by the use of grain yields of a randomly chosen group of 277 varieties from a world collection, grown in replicated trials for several seasons at three sites in South Australia For each variety a linear regression of yield on the mean yield of all varieties for each site and season was computed to measure variety adaptation In these calculations the basic yields were measured on a logarithmic scale, as it was found that a high degree of linearity was thereby induced The mean yield of all varieties for each site and season provided a quantitative grading of the environments; and from the analysis described, varieties specifically adapted to good or poor seasons and those showing general adaptability may be identified The study of the adaptation of the whole population of varieties was facilitated by the use of a two-dimensional plot (scatter diagram), with mean yield and regression coefficient as coordinates for each variety Though wide variation was evident in both mean yield and sensitivity to environment as characterized by the regression coefficient, the variation in sensitivity was proportionately less among varieties with higher mean yield, and the varieties with highest mean yield exhibited, within very narrow limits (regression coefficients close to 08), a similar degree of adaptation to all environments over the wide range, especially of seasonal conditions, typical of the South Australian cereal belt Varieties from particular geographic regions of the world showed a similarity in type of adaptation, which provides a useful basis for plant introduction Phenotypic stability and physiological and morphological characteristics of groups of varieties with specific or general adaptability are discussed in relation to plant introduction and breeding

Drought resistance in spring wheat cultivars, 1. Grain yield responses.

Abstract: With a view to understanding the basis of cultivar differences in yield under drought, a wide range of cereal cultivars representing durum wheats (Triticum turgidum L.), triticales (X Tritosecale Wittmack), barleys (Hordeum vulgare), and especially tall and dwarf bread wheats (T. aestivum L.) were studied in field experiments in north-western Mexico over three seasons. Drought was created in this rain-free environment by permanently terminating irrigation at various stages before anthesis. Control treatments were well watered throughout the growing period. Detailed measurements of plant water status, leaf area and dry matter production, anthesis date, yield components and grain yield were made. This paper presents primarily the grain yield data. Drought levels were such that the mean yield of all cultivars under drought ranged from 37 to 86% of control yield, corresponding to irrigation cut-offs varying from 69 days before mean anthesis date to only 10 days before. In each experiment the grain yield under drought showed highly significant cultivar differences, which appeared consistent between years. Yields were adjusted for drought escape by using a correction factor which ranged from 2.9 to 8.5 g/m2 per day advance in flowering, being greater in experiments with less severe drought. The demonstration of linear relationships between cultivar yield and drought intensity, as indicated by the mean yield of some or all cultivars, prompted the consideration of cultivar yield under drought as the function of yield potential (Yp, yield without drought), drought susceptibility index (S), and intensity of drought. The cultivar groups showing lowest S values (most droughtresistant) were tall bread wheats and barleys; dwarf bread wheats were intermediate, and durum wheats and triticales were the most susceptible. However, because dwarf wheats have a higher yield potential (Yp) than tall bread wheats, it is suggested that, as a group, tall bread wheats would outyield dwarf wheats only under very severe drought. Also there was considerable within-group variability of S and Yp. Cultivar S values were consistent across experiments. Yield responses of tall and dwarf bread wheat groups obtained in these experiments agreed with those seen in extensive international trials under dryland conditions.

Soil Carbon Fractions Based on their Degree of Oxidation, and the Development of a Carbon Management Index for Agricultural Systems

Abstract: Increasing population pressure is increasing the demand on agricultural systems in many parts of the world and this has often led to the degradation of the soil resource. Soil carbon (C) is a major determinant of sustainability of agricultural systems and changes can occur in both total and active, or labile, C pools. A procedure is presented to determine the degree of lability of soil C. By treating a ground sample of soil with 333 mM potassium permanganate (KMn04) to oxidize a proportion of the carbon and by determining the total carbon by combustion, two fractions of C can be measured. These fractions represent carbon of different lability, with fraction I representing the Labile C (CL), which is oxidized by 333 mM KMn04, and fraction I1 representing the non-labile C (CNL), which is not oxidized by 333 mM KMn04. On the basis of changes in total carbon (CT), a Carbon Pool Index (CPI) is calculated and, on the basis of changes in the proportion of labile C in the soil between a reference site and those subjected to agricultural practice or research treatments, a Lability Index (LI) is determined. These two indices are used to calculate a Carbon Management Index (CMI), with CMI = C Pool Index (CPI) xLability Index (LI) x 100. Analyses of paired samples (cropped and uncropped) from three sites in northern and central New South Wales, Australia, have shown a decline in CPI, a greater decline in LI and hence a decline in the CMI with cropping. Introduction of a legume into a wheat cropping system restored the CMI from 22 to 37 at the Warialda site. Analyses of paired samples from a sugarcane area in north Queensland have shown a decline in CMI in systems dominated by trash burning, but an increase in CMI in systems dominated by green cane trash management. Similar data from Brazil showed no increase in CT with mulching but a 48% increase in CMI due to an increase in the lability of C in the soil. The fractionation procedure and CMI outlined can be used to determine the state and rate of change in soil C of agricultural and natural systems.

Drought resistance, water-use efficiency, and yield potential-are they compatible, dissonant, or mutually exclusive?

Abstract: This presentation is a concept review paper dealing with a central dilemma in understanding, designing, and acting upon crop plant improvement programs for drought conditions. The association among yield potential (YP), drought resistance (DR), and water-use efficiency (WUE) is often misunderstood, which in turn can lead to conceptual oversight and wrong decisions in implementing breeding programs for drought-prone environments. Although high YP is the target of most crop breeding programs, it might not be compatible with superior DR. On the other hand, high YP can contribute to yield in moderate stress environments. Plant production in water-limited environments is very often affected by constitutive plant traits that allow maintenance of a high plant water status (dehydration avoidance). Osmotic adjustment (OA) is a major cellular stress adaptive response in certain crop plants that enhances dehydration avoidance and supports yield under stress. Despite past voiced speculations, there is no proof that OA entails a cost in terms of reduced YP. WUE for yield is often equated in a simplistic manner with DR. The large accumulation of knowledge on crop WUE as derived from research on carbon isotope discrimination allows some conclusions on the relations between WUE on the one hand, and DR and YP on the other, to be made. Briefly, apparent genotypic variations in WUE are normally expressed mainly due to variations in water use (WU; the denominator). Reduced WU, which is reflected in higher WUE, is generally achieved by plant traits and environmental responses that reduce YP. Improved WUE on the basis of reduced WU is expressed in improved yield under water-limited conditions only when there is need to balance crop water use against a limited and known soil moisture reserve. However, under most dryland situations where crops depend on unpredictable seasonal rainfall, the maximisation of soil moisture use is a crucial component of drought resistance (avoidance), which is generally expressed in lower WUE. It is concluded that the effect of a single 'drought adaptive' gene on crop performance in water-limited environments can be assessed only when the whole system is considered in terms of YP, DR, and WUE.

A method for unbiased selective sampling, using ranked sets

Abstract: A new method of sampling is described Take the largest in the first of n sets, each of n random items, the second largest in the second set, and so on to the smallest in the nth set The sample of n items selected in this way is an unbiased sample of the population For typical unimodal distributions the mean of such a sample is slightly less than (n + 1)/2 times more efficient than the mean of n items taken at random The application of the ranked sample method to pasture measurement is discussed