• Authors:
    • Stewart,B. A.
    • Blaser,B. C.
    • Mohammed,S.
  • Source: Journal of Crop Improvement
  • Volume: 26
  • Issue: 1
  • Year: 2012
  • Summary: Water for dryland grain production in the Texas panhandle is limited. Agronomic practices such as reduction in plant population or change in sowing time may help increase maize ( Zea mays L.) yield potential. Tiller formation under dryland conditions leads to more vegetative growth and reduced yield. We hypothesized that clump planting dryland maize would reduce environmental stress, tillering, and vegetative growth, and increase harvest index by having more soil water available during grain filling. Clump planting was studied during 2008 at Bushland, Texas. Two plant populations - 30,000 and 40,000 plants ha -1 - and three plant geometries - clumps of three or four plants (3 PPC or 4 PPC) and equally spaced single plants (ESP) - were grown in 75 cm rows. Growing season precipitation was 209 mm. Harvest index (HI) 200-seed mass and harvested ears were higher in 3 PPC and 4 PPC compared with ESP. Three PPC planted at 40,000 plants ha -1 had the highest harvest index of 0.46. The ESP produced 27% more unproductive ears compared with 3 PPC and 4 PPC. Leaf area index (LAI) was 14% more in ESP than in 4 PPC. The lower population produced higher HI and seed mass than the higher population, regardless of geometry. Grain yields were not significantly higher for clumps, yet increased number of productive ears, seed mass, and HI values, suggesting clump geometry may be a good strategy for dryland maize production.
  • Authors:
    • Mukhwana, E. J.
    • Norton, U.
    • Norton, J. B.
  • Source: Soil Science Society of America Journal
  • Volume: 76
  • Issue: 2
  • Year: 2012
  • Summary: Soils typically show 20 to 40% decline in soil organic carbon (SOC) due to cultivation, most of it in the first 10 yr, but studies on SOC depletion may actually underestimate losses of the original SOC. Starting 40 to 50 yr ago, expanding use of non-inversion tillage, fertilizers, and herbicides lead to reduced disturbance and increased residue production that undoubtedly began recovery of SOC depleted during previous decades when farmers used only intensive tillage to control weeds and stimulate release of nutrients from crop residues. We measured SOC and total N stocks, density fractions, and labile C and N at 10 study sites in two rain-fed production areas in southeastern Wyoming. Systems evaluated include historic inversion-tillage-based winter wheat ( Triticum aestivum L.)-fallow with no inputs, conventional winter wheat-fallow, minimum- and no-till continuous rotations and permanent grass cover. Results were then compared to SOC under nearby native grasslands. Soils beneath historic wheat-fallow were the most depleted in SOC, with 13.8 and 17.6 Mg C ha -1 in the upper 30 cm at the two study areas, or 37% of the SOC under the two native sites. Soil OC contents were statistically similar across conventional, minimum-till, and no-till systems, ranging from 64 to 78% of native SOC levels, and significantly higher under permanent grass, with both sites having 90% of native SOC levels. Free light fraction organic carbon (LFOC) contents were lowest beneath the historic system, but increased in systems with fewer disturbances. When normalized by SOC and total N, the labile C and N pools generally increased with increasing disturbance, especially microbial biomass carbon (MBC) and dissolved organic carbon (DOC). Soil OC contents under the historic, inversion tillage system were much lower relative to native grasslands than found in other studies, which, together with other findings, suggest that SOC levels have begun to recover under the modern conventional system. Free LFOC and labile pool C and N contents indicate that conservation tillage systems in place for a relatively short time are facilitating further recovery of SOC.
  • Authors:
    • Presley, D. R.
    • Sindelar, A. J.
    • Buckley, M. E.
    • Mengel, D. B.
  • Source: Agronomy Journal
  • Volume: 104
  • Issue: 3
  • Year: 2012
  • Summary: Grain sorghum [ Sorghum bicolor (L.) Moench] is an important grain crop grown in both highly productive and marginal areas in the central Great Plains because of the crop's ability to use the erratic precipitation observed in this region. More effective capture and storage of this limited rainfall is needed to improve the productivity and profitability of dryland agriculture. The objective of this study was to determine the effects of long-term tillage and N fertilization on soil physical and hydraulic properties after long-term continuous grain sorghum production. Variables included conventional tillage (CT) and no-till (NT) and four rates of N fertilizer. Selected soil quality indicators included soil organic carbon (SOC), bulk density (BD), wet aggregate stability (WAS), and ponded infiltration. No-till accumulated more SOC in the surface 0 to 5 cm, and was less dense at all depths than CT. When tillage was compared across all N rates, NT contained 30% greater SOC than CT at the 0 to 5 cm. Mean weight diameter (MWD) was larger with increasing N fertilization and eliminating tillage. Ponded infiltration rates were greatest for the high N fertilization rate under NT, and lowest for the 0 kg N ha -1 rate under CT. In this long-term grain sorghum system, increasing N fertilization rate and NT both positively affected soil physical properties. These improvements in hydraulic properties will aid in more effectively capturing unpredictable precipitation, and further underscore the utility of NT management practices for the central Great Plains region.
  • Authors:
    • Seufert, V.
    • Ramankutty, N.
    • Foley, J. A.
  • Source: Nature
  • Volume: 485
  • Issue: 7397
  • Year: 2012
  • Summary: Numerous reports have emphasized the need for major changes in the global food system: agriculture must meet the twin challenge of feeding a growing population, with rising demand for meat and high-calorie diets, while simultaneously minimizing its global environmental impacts. Organic farming - a system aimed at producing food with minimal harm to ecosystems, animals or humans - is often proposed as a solution. However, critics argue that organic agriculture may have lower yields and would therefore need more land to produce the same amount of food as conventional farms, resulting in more widespread deforestation and biodiversity loss, and thus undermining the environmental benefits of organic practices. Here we use a comprehensive meta-analysis to examine the relative yield performance of organic and conventional farming systems globally. Our analysis of available data shows that, overall, organic yields are typically lower than conventional yields. But these yield differences are highly contextual, depending on system and site characteristics, and range from 5% lower organic yields (rain-fed legumes and perennials on weak-acidic to weak-alkaline soils), 13% lower yields (when best organic practices are used), to 34% lower yields (when the conventional and organic systems are most comparable). Under certain conditions - that is, with good management practices, particular crop types and growing conditions - organic systems can thus nearly match conventional yields, whereas under others it at present cannot. To establish organic agriculture as an important tool in sustainable food production, the factors limiting organic yields need to be more fully understood, alongside assessments of the many social, environmental and economic benefits of organic farming systems.
  • Authors:
    • Hoogmoed, W. B.
    • Oenema, O.
    • Cai D.
    • Jin, K.
    • Wu, X.
    • Zhao, Q.
    • Feng, Z.
    • Zhang, D.
    • Dai, K.
    • Wu, H.
    • Wang, X.
  • Source: Field Crops Research
  • Volume: 132
  • Year: 2012
  • Summary: Dryland farming in the dry semi-humid regions of northern China is dominated by mono-cropping systems with mainly maize ( Zea mays L.) or wheat ( Triticum aestivum), constrained by low and variable rainfall, and by improper management practices. Addressing these problems, field studies on tillage and residue management for winter wheat and spring maize were conducted at 4 sites in Linfen, Tunliu and Shouyang (Shanxi province) and Luoyang (Henan province). These studies (a.o.) explored the impacts of different tillage and residue application methods on soil physical conditions, water storage, water use, water use efficiency (WUE) and crop yields of wheat and maize. An analysis of the results of these studies is presented. Conservation tillage, comprising no-till as well as reduced tillage practices (subsoiling, deep ploughing) showed benefits which were more prominent in combination with residue application. Benefits compared to conventional tillage were found in the form of improved soil physical conditions, such as higher topsoil bulk densities but lower subsoil bulk densities. This resulted in a better water storage during the summer fallow or rainy season in winter wheat fields, and a better water conservation and soil protection in spring maize fields. Compared to conventional methods, reduced tillage gave yields around 13-16% higher in spring maize and round 9-37% higher in winter wheat. Yields under no-till were very close to those from conventional methods. Surface application of crop residue for maize was found to increase the risk for delayed seedling emergence, because of low temperatures, leading to a recommendation for incorporation of residue in combination with reduced tillage. For winter wheat, subsoiling in combination with straw mulching after harvest in summer every other two or three year, and no-till seeding is a promising practice for sandier soils and low rainfall conditions. For heavier clay loam soils, deep ploughing with straw mulching after wheat harvest in summer every other two or three year, and no-till seeding practice is recommended. For spring maize, deep ploughing with straw and fertilizers incorporation after harvest in fall, and no-till seeding practices are recommended. Subsoiling or no-till with residue mulching after harvest in fall, and no-till seeding practices in spring are also promising practices, the latter only in situations where low spring temperatures are not a problem. Continuous no-till is not recommended.
  • Authors:
    • Qiu, G.
    • Geng, S.
    • Tsuji, W.
    • Moritani, S.
    • Inoue, M.
    • Wang, S.
    • Zhang, Q.
    • Xie, Q.
  • Source: Journal of Food, Agriculture & Environment
  • Volume: 10
  • Issue: 1 part 2
  • Year: 2012
  • Summary: Determination of the threshold of soil water potential (psi) at which point irrigation should be considered in horticultural plants is important for efficient water use, especially in drylands. The purpose of this study was to determine the threshold for scheduling irrigation during the last week of stage 1 of berry development. Pione grapevine ( Vitis vinifera L., cv. V. labrasca) was allowed to experience decreasing psi monitored by tensiometers after an irrigation event. Berry diameters were measured every hour for 5 days using photogrammetry, a new methodology for monitoring berry size. Net photosynthesis and transpiration rates were measured at various intervals by a portable photosynthesis system. The results showed that after irrigation, the psi decreased slowly during the first 2 days, but started decreasing rapidly when it decreased -6.2 kPa at 10 cm soil depth. Berry diameters increased at night and decreased during the day, and were sensitive to soil moisture status. Berry diameter increased rapidly after irrigation till psi became -3 kPa. In the psi range of -3 to -5.4 kPa, the growth rate decreased, and as psi decreased beyond -5.4 kPa, the berry started shrinking and the shrinkage showed a strong linear relationship with decreasing psi. However, photosynthesis and transpiration rates were unaffected until psi became -9.3 kPa or less. Thus, berry diameter was a more sensitive indicator of water stress than photosynthesis and transpiration. The value of -5.4 kPa should be considered as the threshold psi for scheduling irrigation in the last phase of stage 1 of berry development in grapevines.
  • Authors:
    • Li, F.
    • Gan, Y.
    • Li, X.
    • Si, J.
    • Xiong, Y.
    • Liu, C.
    • Jin, S.
    • Zhou, L.
  • Source: Field Crops Research
  • Volume: 126
  • Year: 2012
  • Summary: Understanding plant-soil relationships may help maximize crop productivity while maintaining and improving soil quality. Field experiments were conducted in 2006 and 2007 at the Dryland Agricultural Experimental Station of the Loess Plateau, Lanzhou University, China, to determine the effects of various ridge-furrow and plastic-mulching techniques on the growth and yield of maize ( Zea mays L.) and soil biochemical properties. Five treatments were designed: (1) flat-plot sowing without ridge-furrow mulching (CK), (2) large (80 cm) and small (40 cm) ridges alternated and fully mulched with plastic (DRM), (3) on-furrow sowing with plastic mulch applied only on the ridge at a row spacing of 60 cm and 40 cm alternatively (RM), (4) flat-plot sowing with plastic mulch at a row spacing of 60 cm and 40 cm alternatively (NM), and (5) flat-plot sowing with plastic mulch at a row spacing of 80 cm and 40 cm alternatively (WM). The results showed that film mulching enhanced soil microbial biomass; where microbial biomass carbon (MBC) in the DRM treatment reached 633 mg kg -1 at harvest in 2007, three times the MBC of the CK. The MBC:SOC ratios were 8.8%, 7.1%, 5.7% and 5.4% in DRM, RM, NM and WM, respectively. The ridge-furrow with plastic-mulching increased soil light fraction carbon (LFOC) in both years, averaging up to 1.04 g kg -1 at harvest. Underground plant biomass increased substantially in the mulching treatments, especially in DRM. Positive correlations were found between total biomass and LFOC, between MBC and LFOC, and between MBC and available phosphorus (AP), but a negative correlation between SOC and soil mineral nitrogen (MN). The carbon to phosphorus (C/P) ratio was highest in DRM among treatments, but the content of SOC, MN, and C/N ratio in DRM was lowest, suggesting that the DRM treatment strengthened the interactions between maize and soil, and that the increased content of LFOC with time provides a basis for increasing productivity in future years. In conclusion, the ridge-furrow and plastic-mulching technique brought about a challenge in maintaining soil fertility, but this technology provides a potential opportunity of substantially increasing crop yields in semiarid rainfed regions.
  • Authors:
    • Prasad, J.
    • Venkateswarlu, B.
  • Source: Current Science
  • Volume: 102
  • Issue: 6
  • Year: 2012
  • Summary: Carrying capacity (CC) in the context of Indian agriculture, denotes the number of people and livestock an area can support on a sustainable basis. CC is dynamic in nature, varying from time to time based on utilization of resources, technology application and management. In India, rainfed agriculture occupies nearly 58% of the cultivated area, contributes 40% of country's food production, and supports 40% of the human and 60% of the livestock population. The food grains production has increased several fold in the last four decades. During the last decade (TE 1998-99 to TE 2008-09) the production in coarse cereals, oilseeds and pulses increased by 20%, 16% and 3% respectively, primarily due to the yield gains. There is a need to further increase food production substantially for meeting the requirements of the ever-increasing population. This will put tremendous strain on natural resources which are already under stress due to unsustainable utilization. Continuous decline in groundwater levels, growing deficiency of major and micronutrients, declining factor productivity and looming threat of climate change are some of the issues which will have a bearing on food production in the near future. However, the large realizable yield gaps in many rainfed crops, opportunities to increase yields through rainwater harvesting and recycling, soil fertility improvement, crop diversification and effective dissemination of technologies give a hope that future requirements of food can be met, but it requires substantial resources. This article discusses issues constraining rainfed crop production and possible ways to enhance productivity in a sustainable manner.
  • Authors:
    • Berger, P.
    • Santos, D.
    • Silva, T.
    • Aquino, R.
    • Aquino, L.
  • Source: REVISTA BRASILEIRA DE ENGENHARIA AGRICOLA E AMBIENTAL
  • Volume: 16
  • Issue: 4
  • Year: 2012
  • Summary: This work aimed to evaluate the effect of phosphorus application in rainfed and irrigated crop on shoot dry matter, the absorption and nutrient exportation, and yield of cotton crop. The experiment was carried out in a Psament in the northeren part of Minas Gerais State, Brazil. The experimental design was in randomized blocks with four replications in a factorial arrangement of two doses of P 2O 5 * two cropping systems. Two additional treatments in each system without phosphorus application completed six studied treatments. Accumulation of dry biomass, absorption and exportation of nutrients, and yield of seed cotton were evaluated. Phosphorus levels did not influence the accumulation of shoot dry biomass. P supply increased the exportation of P, Ca, Mg, S, and Mn under irrigated and of N, K, and Fe regardless of the cropping system. Irrigation increased the dry biomass of leaves, stems, and shoots at 80 days after emergency, and the absorption of N, P, K, Ca, Mg, S, Cu, Fe, Mn, Zn, and B, as well as their exportation by the crop. There was an increase in the number of bolls per plant, fiber yield and productivity through the irrigation use. Increasing productivity with P application was conditioned to irrigation.
  • Authors:
    • Baraibar, B.
    • Torra, J.
    • Atanackovic, V.
    • Westerman, P.
  • Source: IOBC/WPRS Bulletin
  • Volume: 75
  • Year: 2012
  • Summary: In dryland cereals in NE Spain, the harvester ant, Messor barbarus L., is responsible for a high percentage of seed removal. A direct density dependent response of seed predators to seed patches may help regulate weed populations. In this study, we investigated if seed removal rate by harvester ants is influenced by weed seed density. For this reason, 60 circular areas of 1 m 2 were created inside four 50*50 m blocks after cereal harvest Lolium multiflorum L. seeds were applied at 1000, 2000, 5000, 10000 or 20000 seeds/m 2, in ten randomly selected areas each; the remaining 10 were used to test the methodology used to retrieve the seeds. After 24h, the remaining seeds were collected using vacuum cleaners or a D-vac and seed removal rates were estimated. In three of the four blocks, seed removal was extremely high (99-100%), and the response was therefore density independent Here, nests densities ranged from 468 to 900 nests/ha. In the fourth block seed removal was 91%, and here nest density was lower (284 nests/ha).