• Authors:
    • Agenbag, G. A.
    • Louw, P. J. E.
    • Fourie, J. C.
  • Source: South African Journal of Enology and Viticulture
  • Volume: 28
  • Issue: 2
  • Year: 2007
  • Summary: The trial was conducted over a period of ten years (1993/94 to 2002/03) on a sandy soil in a Sauvignon blanc/Ramsey vineyard near Lutzville (31degrees35′S, 18degrees52′E), situated in the semi-arid Olifants River Valley of the Western Cape. Fourteen treatments, consisting of three grain species and four legumes, managed according to two cover crop management practices, were included. One management practice consisted of cover crops which were sown annually and full surface, post-emergence chemical control which was applied before bud break and when the berries reached pea size (BB). The second management practice consisted of cover crops which were sown biennially. Post-emergence chemical control was applied to the vine row before bud break and full surface when the berries reached pea size (AB). From 1999/2000 to 2002/03 the cover crops were sown annually, while the full surface post-emergence control applied at the end of November was advanced to mid-October. Two treatments in which Avena sativa L. v. Saia ('Saia' oats) and Vicia dasycarpa Ten. (grazing vetch) were sown annually, controlled mechanically in the work row and chemically in the vine row from bud break to harvest (MC), were also applied. These treatments were compared to a control, in which no cover crop was sown and MC was applied. A treatment in which no cover crop was sown and BB was applied (weedchem), was also included. During the third growing season of the vines (1994/95), the grapevine shoot mass of the BB treatments of grazing vetch and Medicago truncatula Gaertn. v. Paraggio ('Paraggio' medic) was significantly more than that of the AB and MC treatments, with the exception of Secale cereale L. v. Henog (AB) and grazing vetch (MC). The first harvest (1994/95) from the grapevines in the BB treatments was significantly higher than that of weedchem and the MC treatments. The grape yield of the BB treatments, grazing vetch (AB) and Ornithopus sativus L. v. Emena (pink Seradella) (AB) was significantly more than that of weedchem and the control during the 1997/98 season. The NO 3-N concentration in the leaf petioles in all the cover crop treatments was, with the exception of the AB treatments of rye, M. truncatula Gaertn. v. Parabinga ('Parabinga' medic) and grazing vetch, significantly higher than that in weedchem and the control, as measured during the 1994/95 season. The NO 3-N concentration in the leaf petioles of the BB and AB treatment of a species differed significantly. The N concentration in the juice of the cover crop treatments during the 1995/96 season was, with the exception of 'Saia' oats (MC) and 'Parabinga' medic (AB), significantly higher than that of weedchem and the control. During the 1998/99 season, the N concentration of the juice in the BB and AB treatments of grazing vetch and pink Seradella was significantly higher than that of the MC treatments, two rye treatments, weedchem and the AB treatments of the other cover crops. The concentration of Ca in the juice of the cover crop treatments was, with the exception of the pink Seradella treatments, significantly higher than that of weedchem and the control. Wine quality did not differ between treatments.
  • Authors:
    • Castillo Gonzalez, F.
    • Perez Olvera, M. A.
    • Navarro Garza, H.
  • Source: Revista Fitotecnia Mexicana
  • Volume: 30
  • Issue: 2
  • Year: 2007
  • Summary: In this study we compared the plant coverage ability and main agronomic characteristics of five plant species in Nonoalco (2250 masl) and Ixayoc (2500 masl) in north eastern State of Mexico. The populations were: Scarlet runner bean ( Phaseolus coccineus), two faba bean varieties ( Vicia faba, var 'Purepecha' and 'V-35'), common vetch ( Vicia sativa), and oat ( Avena sativa var 'Saia'), in an experimental design in random blocks with three replications, in 6*4 m experimental plots. The scarlet runner and faba beans were planted in rows, while the vetch and oat were thrown sowed. The main variables evaluated were: percentage of area coverage and plant height, on four dates; biomass production at 70 d and at harvest, and grain yield. The results showed differences among populations in ground coverage and agronomic characteristics. Oat and vetch had the best ground cover in both sites. Oat showed the highest growth in both sites, and vetch had the second best behavior. The 'Purepecha' faba bean showed the lowest growth in both sites. The highest production of biomass for all populations in both periods, were obtained in Nonoalco because of its physical-chemical soil characteristics.
  • Authors:
    • Marais, G. F.
    • Pakendorf, K. W.
    • Pretorius, Z. A.
    • Prins, R.
    • Komen, J. S.
  • Source: Australian Journal of Agricultural Research
  • Volume: 58
  • Issue: 6
  • Year: 2007
  • Summary: The cultivation of small grain cereals was introduced to South Africa by Dutch settlers in the 17th Century. According to historical records the first documented epidemic of wheat stem rust occurred in the south-western parts of the current Western Cape in 1726. Recurring stem and leaf rust epidemics were associated with expanding wheat production and became particularly severe in the winter-rainfall regions of the Western and Eastern Cape, as well as in the summer-rainfall regions of the Free State. The wheat stripe rust pathogen was first detected in South Africa in 1996. Due to susceptibility of cultivars at the time of this exotic introduction, stripe rust has caused significant losses in commercial wheat production over the past 10 years. Pathotype surveys of Puccinia graminis and P. triticina were initiated in the 1920s, but were discontinued until research on wheat stem rust was resumed in the 1960s. Recent evidence has shown that P. graminis f. sp. tritici continues to evolve. In addition, the annual number of wheat stem rust collections is increasing, emphasising the sustained threat of this damaging pathogen. A stem rust pathotype first detected in 2000, with newly acquired virulence for Sr8b and Sr38, currently constitutes more than 80% of all collections. Leaf and stem rust diseases also occur on barley, oat, triticale, and rye and are important production constraints in several regions. Some studies have described variability in these pathogens but long-term records of pathogenicity changes in barley and oat rust are not available. Cereal rust diseases have clearly played an important role in South African agriculture and many production regions remain favourable for rust development. Current expertise in cereal rusts covers most technologies necessary to study the respective host-pathogen systems. However, a general lack of capacity and fragmentation of research groups prevent a unified approach and remain a challenge for sustainable cereal rust control in South Africa. A national strategy for cereal rust control, with particular emphasis on pathogen and host resources, and breeding for resistance, is urgently needed.
  • Authors:
    • Chauhan, S. K.
    • Baljit, S.
    • Saralch, H. S.
  • Source: Agroforestry: systems and practices
  • Year: 2007
  • Summary: Punjab is the richest state in the country in term of per capita income and has earned the name as food bowl of the country by putting 84-85 per cent of its geographical area under highly intensive, technical and mechanical agriculture with cropping intensity as high as 185 per cent and contributing more than one third of rice and half of its wheat production to the central pool of food reserve. The food grain production in the state has increased approximately twelve times in a span of about 50 years after independence from 20 lac tones in 1950-51 to 234.89 lakh tonnes in 2002-2003. Achieving this high productivity without caring for natural resources has resulted in a considerable loss in the inherent production potential and deterioration of soil health. As a result, man is getting serious warning signals in the form of lowering of water table, drought, high rate of environmental pollution, extremes of climatic parameters, etc. Agriculture in the state has become too intensive, wasteful and reckless and the radical changes are required to maintain the balance. Therefore, there is a strong thinking to diversify farming in the state to maintain the sustainability of the whole system. The state government is stressing hard to save the natural resources through the diversification in traditional crop rotation and adopt resource-conserving measures. With the introduction of fast growing multipurpose tree species in Punjab during sixties, agroforestry has been recognized as a sustainable system of high potential to boost the state's meager forest resources and to check the further degradation of natural resources. Highly productive block planting of poplar intercropped with wheat, sugarcane, turmeric, oats, berseem, mustard, medicinal plants, seasonal flowers, vegetables, etc. has become popular in irrigated tracts of the state. Boundary planting of eucalypts in the wheat- paddy cropping system and scattered trees of kikar, khair, shisham, dek, etc. on cultivated lands under rainfed conditions, especially in the sub-montane foot hill zone, play an important role in soil conservation and boosting the socio-economic status of the farmers. These tree species have inherent potential of increasing the productivity of problematic lands of the state. Therefore, the diversion of farmlands towards agroforestry will not only increase tree cover but also achieve the desired objective of National Forest Policy-1988 and conserve the precious natural resources like ground water, soil, biodiversity, etc. and prove to be a viable alternative sustainable land use system, which is renewable and eco-friendly as compared to sole agricultural crops in the years to come. The profitability of tree plantations on farmers' fields will further improve with the implementation of trading of carbon credits under Kyoto Protocol.
  • Authors:
    • Han, X.
    • Liu, P.
    • Li, L.
    • Huang, J.
    • Sun, O.
    • Zhou, Z.
  • Source: Biogeochemistry
  • Volume: 82
  • Issue: 2
  • Year: 2007
  • Summary: Equilibrium carbon stock is the result of a balance between inputs and outflows to the pool. Changes in land-use are likely to alter such balance, resulting in different carbon stores under different land-use types in addition to the impacts of global climate change. In an agro-pastoral ecotone of Inner Mongolia, northern China, we investigated productivity and belowground carbon and nitrogen stores under six different types of land-uses, namely free grazing (FG), grazing exclusion (GE), mowing (MW), corn plantation (CP), fallow (FL), and alfalfa pasture (AP), and their impacts on litter and fine roots in semiarid grassland ecosystems. We found that there were great variations in aboveground net primary production (ANPP) across the six land-use types, with CP having markedly high ANPP; the FG had significantly reduced soil organic carbon (SOC) and nitrogen stores (SON) to 100 cm depth compared with all other types of land uses, while very little litter accumulation was found on sites of the FG and CP. The top 20 cm of soils accounted for about 80% of the root carbon and nitrogen, with very little roots being found below 50 cm. About 60% of SOC and SON were stored in the top 30 cm layer. Land-use change altered the inputs of organic matters, thus affecting SOC and SON stores accordingly; the MW and GE sites had 59 and 56% more SOC and 61% more SON than the FG. Our estimation suggested that restoring severely degraded and overgrazed grasslands could potentially increase SOC and SON stores by more than 55%; conversion from the native grasses to alfalfa could potentially double the aboveground biomass production, and further increase SOC and SON stores by more than 20%. Our study demonstrated significant carbon and nitrogen storage potential of the agro-pastoral ecotone of northern China through land-use changes and improved management in the context of mitigating global climate change.
  • Authors:
    • Grace,P.
  • Source: Healthy Soils Symposium
  • Year: 2007
  • Authors:
    • Grace, P.
    • Rowlings, D.
    • Peterson, N.
    • Weier, K.
    • Kiese, R.
    • Butterbach-Bahl, K.
  • Source: Non-CO2 Greenhouse Gas Fluxes in Australian-New Zealand Landscapes
  • Year: 2007
  • Authors:
    • McGregor, A.
    • Slattery, B.
    • Ugalde, D.
    • Brungs, A.
    • Kaebernick, M.
  • Source: Soil & Tillage Research
  • Volume: 97
  • Issue: 2
  • Year: 2007
  • Authors:
    • Fan, T.
    • Xu, M.
    • Zhou, G.
    • Ding, L.
  • Source: American-Eurasian Journal of Agricultural and Environmental Science
  • Volume: 2
  • Issue: 5
  • Year: 2007
  • Summary: Grain yield trends and changes in Soil Organic Carbon (SOC) from a 26-yr rainfed fertilization trial in Pingliang, Gansu, China, were recorded. Mean wheat ( Triticum aestivum L.) yields for the 18-yr ranged from 1.72 t ha -1 for the unfertilized plots (CK) to 4.65 t ha -1 for the plots that received Manure (M) annually with inorganic Nitrogen (N) and Phosphorus (P) fertilizers (MNP). Corn ( Zea mays L.) yields for the 6-yr averaged 2.43 and 5.35 t ha -1 in the same treatments. Yields declined with year except the CK for wheat. Wheat yields for the N only declined 117.8 kg ha -1 yr -1 that was the highest among all treatments and that for the NP declined 84.7 kg ha -1 yr -1, similar to that of 77.4 kg ha -1 yr -1 for the treatment receiving straw and N annually and P every second year (SNP). Likewise, the corn yields declined highly for all treatments and the declined amounts ranged from 108 to 258 kg ha -1 yr -1 that was much higher than in wheat. SOC gradually increased with time except the CK and N treatments, in which SOC remained almost stable. The SOC increases of 190.1, 166.8 and 164.5 mg C kg -1 yr -1 occurred in MNP and SNP and M treated soils, respectively. About 24% of the total C-input from manure and root residue and about 14% of the total C-input from straw and root residue remained in the soil as organic matter. Losses of 1 t SOM ha -1 were associated with a decrease in wheat yield of approximately 80 kg ha -1, showing the importance of using management practices that minimize losses of SOC in the China Loess Plateau. Grain yield declines were likely related to gradual dry weather and soil available N decline. It is concluded that C sequestration can be enhanced by increasing manure and straw additions in these dryland soils.
  • Authors:
    • Li, F.
    • Ma, Q.
    • Wang, Z.
    • Li, X.
  • Source: Soil & Tillage Research
  • Volume: 95
  • Issue: 1
  • Year: 2007
  • Summary: The effects of cultivation and overgrazing on soil quality in arid regions have been rarely addressed. This study investigated the roles of cropping and grazing in soil organic C pools and aggregate stability at 0-20 cm depth by comparing conventional grazing (non-fenced ever), intensive grazing (fenced for 22 years) and cropping (cultivated for 40 years) in the arid Hexi Corridor of northwestern China. Total soil organic C (TOC) under non-fenced grazing was 21.6 g kg-1 (or 52.9 Mg ha-1), which was 19.9% (or 13.2% mass per area) lower than that under fenced grazing, because of lower stable organic C fraction (0.25 mm) in total aggregates and mean weight diameter were 15% and 0.28 mm under cropping, significantly lower than 65% and 3.11 mm under non-fenced grazing and 65% and 2.84 mm under fenced grazing. The aggregates of >1 mm were almost entirely demolished under cropping when subjected to wet sieving. Reduction of soil carbohydrates under cropping was closely related to the decline in aggregate water-stability. The negative effects of cropping on soil organic C pool and aggregate water-stability may suggest that cropping on this arid grassland is not sustainable unless no-tillage is adopted. In favor of increasing soil carbohydrates and maintaining soil aggregation, fenced-grazing would be a better option than cropping and non-fenced grazing for the management of arid grasslands.