Effects of spatial and temporal regulation of drip emitters and tube configurations on water productivity of juvenile macadamia trees in the tropics

Macadamia in Australia is traditionally grown in semi-arid climates with hot and humid summers and cool winters supporting rainfed cultivation. Recent industry expansion into more northern, drier production areas of Queensland, Australia, requires supplementary irrigation for successful macadamia production. However, ever-increasing demand for irrigation water in these areas is both competitive and regulated. Limited information is available to optimize water use efficiency for field-grown macadamia trees. We trialled a technique that employs specially designed drip tubes with push-in emitter plugs to close emitters so that transplanting can start with emitters closed distant from tree bases and open next to the trunks of each tree. Additional emitters are then gradually opened (i.e., plugs are removed) as tree canopy size increases over subsequent years. This technique was tested on single and double in-line irrigation tube configurations per row of macadamia. Temporal regulation of emitter closure significantly reduced irrigation input by 75, 50 and 25% in the first, second and third year of treatment. Hence, irrigation over the three-year establishment period was reduced to one-half that of the non-regulated crop. These early reductions of irrigation in juvenile trees had no significant negative effects on plant growth (height, canopy spread, leaf chlorophyll and leaf photosynthetic rates), nor on nut counts. Control of emitter discharge between the plants along the row in the earlier stage (i.e., before complete within-row canopy cover) also reduced weed growth between the trees in the row. Notable growth advantages of the single in-line over the double in-line tube configuration were evident, with a non-significant but sizeable benefit on nut counts too. Effects of the temporal regulation of emitters and of in-line tube configurations must be validated on cultivars with differing water requirements and for the longer-term reproductive performance and nut quality

Leaf Litter Decomposition and Mitigation of CO₂ Emissions in Cocoa Ecosystems

Studies simultaneously quantifying litter weight losses and rates of CO2-C evolved are few, though essential for accurate estimates of forest carbon budgets. A 120-day dry matter loss and a 130-day carbon emission experiments were concurrently conducted at the soil laboratory of the University of Reading, UK. Leaf litters of tree species comprising cocoa (Theobroma cacao), Newbouldia laevis (dominant shade tree in Eastern region (ER)) and Persea americana (dominant shade tree in Western region (WR)) of Ghana were incubated using a single tree leaf litter and/or a 1:1 mixed species leaf litters to determine and predict the litter decomposition and C dynamics in cocoa systems with or without the shade trees. Decomposition and C release trends in the ER systems followed: shade > mixed cocoa-shade = predicted mixed litter > cocoa; and in the WR, the order was: cocoa = mixed cocoa-shade > predicted mixed > shade. Differences between released C estimated from litter weight loss and CO2-C evolution measurement methods were not consistent. Regression analysis revealed a strong (R2 = 0.71) relationship between loss of litter C and the CO2-C evolution during litter decomposition. The large C pool for shaded cocoa systems indicates the potential to store more C and thus, its promotion could play a significant role in atmospheric CO2 mitigations

Tradeoffs between pasture production and plant diversity and soil health attributes of pasture systems of Central Queensland, Australia

The clearing land of trees and introduction of exotic pastures to enhance pasture production and associated monetary gains has been a common practise in Queensland. Previous studies on tree clearing emphasised the gains in pasture production, but over periods of less than 10–15 years after clearing, thus potentially misleading land managers who plan to continue grazing beyond that time. The present research follows an integrated approach to quantify the pasture yield and the effects of tree clearing on pasture species composition, soil properties (organic carbon, available N (NO3−), pHw and microbial biomass (C and N)), and litter production over time-since-clearing on a grazing property in central Queensland, and to evaluate the implications of our findings for the region. The cleared pasture systems were taken at <5, 11–13 and >33 year age of clearing in comparison to their paired uncleared pastures for three major tree communities representative of the region: Eucalyptus populnea, Eucalyptus melanophloia and Acacia harpophylla. The paper evaluates the effects of clearing on individual attributes as well as an integrated effect of these attributes, i.e. overall ecological services. Pasture production generally increased with clearing but plant diversity, litter production and potential return of N and P through litter decreased. Among soil attributes, clearing of trees adversely impacted upon soil pH and microbial biomass, which play an important role in nutrient availability and mineralisation. This, the initial gains in pasture production are not sustainable over time. The multivariate analysis for such ecological attributes suggests that at the >33 year age of clearing, the ecological state of pasture systems changed compared to that at 5 year or 11–13 year or to the uncleared system. A disturbed pasture system will most likely take longer to revert to the original state compared to the time that would have taken to harvest the benefits. The results are important for landholders and policy makers to comprehend the real gains and losses following tree clearing for pasture development over the long term

Carbon storage in Ghanaian cocoa ecosystems

Background: The recent inclusion of the cocoa sector as an option for carbon storage necessitates the need to quantify the C stocks in cocoa systems of Ghana. Results: Using farmers’ fields, the carbon (C) stocks in shaded and unshaded cocoa systems selected from the Eastern (ER) and Western (WR) regions of Ghana were measured. Total ecosystem C (biomass C + soil C to 60 cm depth) ranged from 81.8 to 153.9 Mg C/ha. The bulk (~89 %) of the systems’ C stock was stored in the soils. The total C stocks were higher in the WR (137.8 ± 8.6 Mg C/ha) than ER (95.7 ± 8.6 Mg C/ha). Conclusion: Based on the cocoa cultivation area of 1.45 million hectares, the cocoa sector in Ghana potentially could store 118.6–223.2 Gg C in cocoa systems with cocoa systems aged within 30 years regardless of shade management. Thus, the decision to include the cocoa sector in the national carbon accounting emissions budget of Ghana is warranted

Silvicultural management of bamboo in the Philippines and Australia for shoots and timber : Proceedings of a workshop held in Los Baños, the Philippines, 22-23 November 2006 /

"There is a push at the national and international levels to (re)introduce perennial species into cropping and ‘at-risk’ lands, capitalising upon their more notable ecosystem service properties of containing soil and water erosion, protecting soil carbon reserves and sequestering atmospheric carbon dioxide on a real-time basis. ...The peer-reviewed papers contained herein provide an opportunity to fully report on the research. They will act as a valuable resource for people interested in the sustainable production and use of bamboo."--p. 3

The inaugural lecture: Agriculture and the modern society

"Good evening. This is the 6 o'clock news for today June 4th 2017. The eight billionth human was today born in Burkina Faso, to the parents of one child in the village of Donsin. Planet Earth, though, now supports 16% more people than it did at the beginning of this century. The United Nations, marking this occasion, referred to the monumental changes in research and policy implemented at the end of the 20th century which permit the eight billionth human to enjoy the promises of health, education, rural development and ...

Rainfed Agriculture: Unlocking the Potential. Comprehensive Assessment of Water Management in Agriculture Series 7. Edited by S. P. Wani, J. Rockstrom and T. Owels. Wallingford, UK : CABI (2009) : [book review]

The introduction of this book states that water is an important driver to achieve four of the Millennium Development Goals. Using this argument, the book focuses on the challenges of how to deal with extreme rainfall variability in the semi-arid tropics (SAT) for the benefit of agriculture, mainly cereal production. For those who wish to be apprised of the current thinking and practice in the capture of rainfall, and its use as supplemental irrigation for rainfed crops, with emphasis on the SAT of West and South Asia and NorthAfrica, then this is the ideal up-to-date source. The book deserves to be browsed chapter by chapter, although as with most edited texts, the quality and relevance of chapters vary enormously. For the reader wishing to read cover to cover, verbatim duplication between and within chapters and of the repetitions of justification for, and the outcomes of, the research will become tedious. Principles grounded in one area are likely to be similar in another. Major detractions are: from an environmental perspective, the lack of discussion of negative impacts on wildlife due to impounding of overland water flows; from a social perspective, absence of discussion on the impact of reduced availability of water for domestic usage; and from a geographic perspective, the missing yet relevant deliberations from the American and Australian continents. Notwithstanding these, the book presents important contributions towards a more efficient capture and use of rainfall, with a major focus on engineering and agronomic practices, but also elaborating on the necessary genetic enhancement

'Physiology of crop production’ by NK Fageira, VC Baligar and RB Clark, Haworth Press : [book review]

The cover of Physiology of Crop Production states that it provides cutting-edge research and data for the complete coverage of the physiology of crop production. The book is lacking on both accounts. Less than 3 % of the references dating from 2000 onwards can hardly justify the claim as cutting edge, and with examples primarily from cereal and grain legume crops and a focus on inceptisols and oxisols of Brazil, the content may interest only a section of the intended readership.The writing style is inconsistent throughout. Contributions from the three authors quite clearly stand apart and there is little cross-referencing between chapters. The text gives the impression of still being in a draft form, with numerous grammatical and textual errors evident to a perceptive reader. The reproduction of most of the figures is of poor quality – dot-matrix generated legends do not do justice to the data presented. Line spacingis inconsistent, especially on pages with figures and tables. Incorrect usage of some statistical terminology and units will send mixed messages to students amongst the intended readership. Sections repeated, at times verbatim, will be annoying to those who read the complete text. To its credit, the chapter on Carbon Dioxide and Crop Yield is well written, but it is short. Although much published information has been compiled throughout the text, the book on the whole fails to integrate existing knowledge on crop physiology into a clear understanding that will, as the new-book announcement claims, maximize crop production anywhere in the world. That is a tall order for any single book

Intensive organic production systems and issues of sustainability

Sustainability, variously described as a ‘journey rather than a destination’ to a ‘composite quality’ defies exact definition. Differentiation of sustainability into component indicators is somewhat easier to grapple with; sustained productivity, economic viability and guaranteed product quality are a few of the obvious parameters that may be easily quantified. Indeed, organic productions systems (OPS) are recognised as providing produce quantitatively free of agrochemicals, and with high nutritive value, but their impact (ideally positive) on landscapes, ecosystems and environmental quality, the substance of Environmental Management Systems, are less quantifiable. For better or worse, the expected environmental outcomes of OPS are wide-ranging, and possibly not achievable. A recent survey of organic customers (Meldrum 2006) shows that > 75% believe OPS are better for the environment; and it is up to the scientific community to substantiate these beliefs and to develop guidelines to ensure that OPS are better for the environment. With a focus on intensive horticulture in the tropics and subtropics, I consider the contributions to OPS and environmental sustainability of live mulching and organic amendments. Their primary roles as nutrient sources, as conditioners of soil physical quality, as determinants of cation exchange capacity, and as major contributors to the maintenance of soil organic matter are discussed, as too are interactions between these, and their relationships to the topical issues of sequestration of atmospheric carbon. I argue that well defined criteria with respect to expectations for each of these roles must be adhered to in order to ‘journey towards the composite quality of sustainability’