31. Soil organic carbon dynamics in a dryland cereal cropping system of the Loess Plateau under long-term nitrogen fertilizer applications.

• Authors:
  • Liu, W. Z.
  • Li, Y.
  • Zhu, H. H.
  • Coleman, K.
  • Wu, J. S.
  • Guo, S. L.
• Source: Plant and Soil
• Volume: 353
• Issue: 1/2
• Year: 2012
• Summary: Aims: Concerns over food security and global climate change require an improved understanding of how to achieve optimal crop yields whilst minimizing net greenhouse gas emissions from agriculture. In the semi-arid Loess Plateau region of China, as elsewhere, fertilizer nitrogen (N) inputs are necessary to increase yields and improve local food security. Methods: In a dryland annual cropping system, we evaluated the effects of N fertilizers on crop yield, its long-term impact on soil organic carbon (SOC) concentrations and stock sizes, and the distribution of carbon (C) within various aggregate-size fractions. A current version (RothC) of the Rothamsted model for the turnover of organic C in soil was used to simulate changes in SOC. Five N application rates [0 (N0), 45 (N45), 90 (N90), 135 (N135), and 180 (N180) kg N ha -1] were applied to plots for 25 years (1984-2009) on a loam soil (Cumulic Haplustoll) at the Changwu State Key Agro-Ecological Experimental Station, Shaanxi, China. Results: Crop yield varied with year, but increased over time in the fertilized plots. Average annual grain yields were 1.15, 2.46, 3.11, 3.49, and 3.55 Mg ha -1 with the increasing N application rates, respectively. Long-term N fertilizer application increased significantly ( P=0.041) SOC concentrations and stocks in the 0-20 cm horizon. Each kilogram of fertilizer N applied increased SOC by 0.51 kg in the top soil from 1984 to 2009. Using RothC, the calculated annual inputs of plant C (in roots, stubble, root exudates, etc.) to the soil were 0.61, 0.74, 0.78, 0.86, and 0.97 Mg Cha -1 year -1 in N0, N45, N90, N135 and N180 treatments, respectively. The modeled turnover time of SOC (excluding inert organic C) in the continuous wheat cropping system was 26 years. The SOC accumulation rate was calculated to be 40.0, 48.0, 68.0, and 100.0 kg C ha -1 year -1 for the N45, N90, N135 and N180 treatments over 25 years, respectively. As aboveground biomass was removed, the increases in SOC stocks with higher N application are attributed to increased inputs of root biomass and root exudates. Increasing N application rates significantly improved C concentrations in the macroaggregate fractions (>1 mm). Conclusions: Applying N fertilizer is a sustainable practice, especially in carbon sequestration and crop productivity, for the semiarid Loess Plateau region.

32. Alternate furrow irrigation effect on radiation use efficiency and forage quality of foxtail millet ( Setaria italica).

• Authors:
  • Hosseini, S. M. B.
  • Jahansooz, M. R.
  • Heidari, H.
  • Chaichi, M. R.
• Source: Annals of Biological Research
• Volume: 3
• Issue: 6
• Year: 2012
• Summary: The aim of the study was to determine the effect of alternate irrigation method and deficit irrigation on radiation use efficiency and forage quality of foxtail millet ( Setaria italica) under a double cropping system after barley ( Hordeum vulgar). Conventional furrow irrigation (M1) and alternate furrow irrigation (M2) methods and different deficit irrigation levels including 100, 85, 70 and 55% of crop water requirement (V1, V2, V3 and V4) were tested in a field experiment on the west of Tehran, Iran for 2 years (2008 and 2009). Results showed that alternate furrow irrigation with 85% of crop water requirement (M2V2) had the highest Absorption Ratio of Photosynthetically Active Radiation (PARAR) and Cumulative Absorption of Photosynthetically Active Radiation (PARCA) in 2008 (P

33. Partial rootzone drying increases water-use efficiency of lemon Fino 49 trees independently of root-to-shoot ABA signalling.

• Authors:
  • Dodd, I. C.
  • Pérez-Pérez, J. G.
  • Botía, P.
• Source: Functional Plant Biology
• Volume: 39
• Issue: 5
• Year: 2012
• Summary: To determine whether irrigation strategy altered the sensitivity of Citrus leaf gas exchange to soil, plant and atmospheric variables, mature (16-year-old) Fino 49 lemon trees ( Citrus limon (L.) Burm. fil. grafted on Citrus macrophylla Wester) were exposed to three irrigation treatments: control (irrigated with 100% of crop potential evapotranspiration, ET c), deficit irrigation (DI) and partial rootzone drying (PRD) treatments,which received 75% ET c during the period of highest evaporative demand and 50% ET c otherwise. Furthermore, to assess the physiological significance of root-to-shoot ABA signalling, the seasonal dynamics of leaf xylem ABA concentration ([X-ABA] leaf) were evaluated over two soil wetting-drying cycles during a 2-week period in summer. Although stomatal conductance ( gs) declined with increased leaf-to-air vapour pressure deficit (LAVPD), lower leaf water potential and soil water availability, [X-ABA] leaf was only related to stomatal closure in well irrigated trees under moderate (

34. Partial root drying as strategy for water use optimization in a 'Tahiti' lime orchard under the semi-arid of Bahia State.

• Authors:
  • Santana, J. A. D. V.
  • Carvalho, G. C.
  • Machado, V. V.
  • Daniel, R.
  • Coelho, E. F.
  • Coelho Filho, M. A.
  • Sampaio, A. H. R.
  • Santana Junior, E. B.
• Source: Acta Horticulturae
• Issue: 928
• Year: 2012
• Summary: The management of irrigation using partial root drying (PRD) was tested in an orchard of 'Tahiti' lime in the semi-arid conditions of Iacu, BA. Six treatments were evaluated: T1, T2, T3 (50% ETc PRD) with plants irrigated by a microsprinklers with its position alternating every 7, 14 or 21 days, respectively, and wetting on opposite sides of the root system; T4 (DI 50% ETc) irrigation was fixed on one side using one emitter per plant, T5 (100% ETc) was the control treatment using two microsprinklers per plant in a fixed position. In T6, at each interval of 21 days, one and two micro-sprinklers were alternatively used per plant. Results demonstrated significant differences in fruit production by the Scott Knott test (p

35. Soil Carbon Dioxide Emissions from Sorghum-Sunflower Rotation in Rainfed Semi-arid Tropical Alfisols: Effects of Fertilization Rate and Legume Biomass Incorporation

• Authors:
  • Sharma, K. L.
  • Venkateswarlu, B.
  • Ramesh, V.
  • Wani, S. P.
• Source: Communications in Soil Science and Plant Analysis
• Volume: 43
• Issue: 14
• Year: 2012
• Summary: The long-term effects of plant legume [horse gram (Macrotyloma uniflorum)] biomass incorporations were assessed in terms of carbon dioxide (CO2) emissions, soil quality parameters, and climatically influenced soil parameters in a dryland Alfisol under varying soil fertility conditions. Six selected treatments consisted of off-season legume incorporation (I) and no incorporation/fallow (F), each under three varying nitrogen and phosphorus fertilizer levels (viz., N0P0, N25P30, and N50P30). Soil moisture, soil temperature, soil surface carbon dioxide emission, soil dehydrogenases, and microbial biomass carbon (MBC) were monitored at three different crop situations [viz., Kharif period (KP), legume/fallow period (LP), and no crop period (NP)] at 14 different periods of the year. Incorporation practices resulted in greater rates of CO2 emission over fallow conditions during the Kharif and legume periods, whereas the emission rate was greater in fallow soils during the end of the legume and no crop periods. The increased rates of fertilizer doses also significantly increased the soil CO2 flux during the majority of the measurements. Beneficial effects of incorporation practices were observed in terms of high soil moisture (5-11%), low soil temperature (3-7%), and high content of MBC over without incorporations. Correlation studies indicated that the soil property MBC was found to be the greatest significant variable with CO2 emission in all the fertilizer treatments under biomass-incorporated soils. These results indicated the undesirable (in terms of CO2 fluxes) and desirable (soil biological and other parameters) effects of legume biomass incorporation and fertilizer application and their significance in improving soil quality and greenhouse gas (GHG) emissions in dryland Alfisols of semi-arid tropics.

36. Climate change effects on organic carbon storage in agricultural soils of northeastern Spain.

• Authors:
  • Easter, M.
  • Alvaro-Fuentes, J.
  • Paustian, K.
• Source: AGRICULTURE ECOSYSTEMS & ENVIRONMENT
• Volume: 155
• Year: 2012
• Summary: The interactive effects of climate change and atmospheric CO 2 rise could have potential effects on both soil organic carbon (SOC) storage and the capability of certain management practices to sequester atmospheric carbon (C) in soils. In this study, we present the first regional estimation of SOC stock changes under climate change in Spanish agroecosystems. The Century model was applied over a 80-yr period (i.e., from 2007 to 2087) to an agricultural area of 40,498 km 2 located in northeast Spain under five different climate scenarios. The model predicted an increase in SOC storage in the 0-30 cm soil depth in all the climate change scenarios tested (i.e., ECHAM4-A2, ECHAM4-B2, CGCM2-A2 and CGCM2-B2). Among climate change scenarios, SOC stock changes ranged from 0.15 to 0.32 Tg C yr -1. The Century model also predicted differences in SOC sequestration among agricultural classes. At the end of the simulation period, the greatest SOC stocks were found in the rainfed arable land under monoculture and no-tillage (MC-NT) class and in the grape-olive (GO) class with average stocks greater than 80 Mg C ha -1. On the contrary, both the alfalfa (AF) and the cereal-fallow (CF) classes showed the lowest SOC stocks with predicted values lower than 60 Mg C ha -1. Under climate change conditions, Spanish agricultural soils could act as potential atmospheric C sinks. Nevertheless, both the magnitude of the change in climate and the adoption of beneficial management practices could be critical in maximizing SOC sequestration.

37. Yield and water productivity of Bt cotton ( Gossypium hirsutum) as influenced by temperature under semi-arid conditions of north-western India: field and simulation study.

• Authors:
  • Sood, A.
  • Jalota, S. K.
  • Buttar, G. S.
  • Bhushan, B.
• Source: INDIAN JOURNAL OF AGRICULTURAL SCIENCES
• Volume: 82
• Issue: 1
• Year: 2012
• Summary: Cotton cultivation in semi-arid region of Indian Punjab is considered as most risky crop as its yield is very sensitive to weather parameters like rain and temperature. In future due to global warming increase in the temperature is expected, which is most likely to influence the growth and yield of this fiber crop like other cereal crops. Studies on the effect of temperature on the growth and seed yield of Bt cotton in this region are lacking. The present 2-year field and 15-year simulation studies concern to simulate the effect of temperature on duration of pheno-phases and seed yield of Bt cotton hybrid RCH 134 and also on crop water productivity. Simulations were run for 15 years (1991-2005) using the already customized CropSyst model. The simulated results indicated that with increase in temperature from 28 to 32degreesC, cotton seed yield was reduced to half (from 4 700 to 2 300 kg/ha) following a linear relation with high coefficient of determination (0.97), and the reduction was more with increased temperature during sowing to flowering stage than other pheno-phases. Total evapo-transpiration (ET) during crop period and crop water productivity was also decreased with increased temperature. Relationship of cotton seed yield was linear with ET and quadratic with total water supply (rain+irrigation). Real crop water productivity (yield/ET) and apparent crop water productivity (yield/irrigation water) were 0.3620.129 and 0.4850.120 kg/m 3, respectively.

38. Changes in soil organic matter indices following 32 years of different wheat production management practices in semi-arid South Africa

• Authors:
  • Du Preez, C. C.
  • Kotze, E.
  • Loke, P. F.
• Source: Nutrient Cycling in Agroecosystems
• Volume: 94
• Issue: 1
• Year: 2012
• Summary: Soil organic matter (SOM) degradation is common in semi-arid regions due to frequent and intensive cultivation, removal of crop residues after harvesting and warmer environmental conditions. Therefore, we evaluated the effects of long-term wheat production management practices on organic matter content of a Plinthosol in semi-arid South Africa. The treatments included two methods of straw management (unburned and burned), three methods of tillage (no-tillage, stubble mulch and ploughing) and two methods of weeding (chemical and mechanical). Soil samples were collected in 2010 at various depths and analysed for soil organic carbon (SOC), soil total nitrogen (STN) and soil total sulfur (STS) as organic matter indices. Treatments where straw was not burned had greater STN and STS, but lower SOC levels than those where straw was burned. No-tillage had higher SOC levels than the stubble mulch and ploughing treatments only in the 0-50 mm soil layer. Below 100 mm soil depth, higher SOC levels were recorded in the ploughed plots. No-tillage and stubble mulch enhanced STN throughout the soil profile compared to ploughing. Ploughing and stubble mulch treatments had greater STS levels than no-tillage treatments in the upper 250 mm soil layer, and STS in the 0-450 mm soil layer was higher in mechanically weeded plots than in chemically weeded plots. Treatment combinations also showed some significant interactions on these indices, but lack of consistency made it difficult to single out the combination that was superior to others. However, to maintain or improve SOM of this Plinthosol priority should be given to no-tillage and stubble mulch management practices. Wheat grain yields over the 32 years trial period were significantly influenced by straw management and tillage methods, but not by weeding methods.

39. Nitrogen fixation by pea and lentil green manures in a semi-arid agroecoregion: effect of planting and termination timing

• Authors:
  • Zabinski, C. A.
  • Burgess, M. H.
  • Miller, P. R.
  • Jones, C. A.
  • McCauley, A. M.
• Source: Nutrient Cycling in Agroecosystems
• Volume: 92
• Issue: 3
• Year: 2012
• Summary: Crop-fallow systems dominate many semi-arid agricultural regions despite fallow's negative effects on soil and water quality. Annual legumes grown as a fallow-replacement crop, and terminated prior to maturity, can reduce these negative effects without substantially decreasing plant available water for the subsequent crop. Interest in growing legume green manures (LGMs) in synthetically-fertilized systems is increasing in the northern Great Plains of North America, partly due to the N-fixing capabilities of legumes; however, little is known about the effects of planting and termination time on N fixation amounts in the region. A 2-year field study was initiated in southwest Montana to determine the effects of planting time (spring or summer) and termination time (e.g. flower or pod) on the amount of N fixed by field pea (Pisum sativum cv. Arvika) and lentil (Lens culinaris cv. Richlea). Two methods, N-15 natural abundance and N difference, were used to quantify N fixation, with wheat or in-crop weeds as reference plants. In 2009, N fixed by spring-planted lentil was higher by pod than flower (P = 0.03). Termination time did not affect the amount of N fixed by spring-planted pea, despite more biomass by pod than flower. In 2010, both spring-planted crops fixed more N by pod than flower (P < 0.01) and more N was fixed by spring-planted than summer-planted crops (P < 0.01). These results should prove useful to growers interested in selecting management practices that optimize N fixation of LGMs.

40. Sustaining agronomic productivity and quality of a Vertisolic soil (Vertisol) under soybean-safflower cropping system in semi-arid central India.

• Authors:
  • Sharma, S. K.
  • Vittal, K. P. R.
  • Kundu, S.
  • Singh, A. K.
  • Lal, R.
  • Venkateswarlu, B.
  • Srinivasarao, C.
  • Sharma, R. A.
  • Jain, M. P.
  • Chary, G. R.
• Source: Canadian Journal of Soil Science
• Volume: 92
• Issue: 5
• Year: 2012
• Summary: Enrichment of soil organic carbon (SOC) stocks through sequestration of atmospheric CO 2 in agricultural soils is important because of its impacts on improving soil quality and agronomic production, and also for adaptation to and mitigation of climate change. Thus, a 15-yr soil fertility management experiment was conducted in the semi-arid tropical region of central India to evaluate the impact of crop residue C input on soybean ( Glycine max L.)-safflower ( Carthamus tinctorius L.) cropping sequence and SOC sequestration in soils of Vertisolic order (Vertisols). Retention of crop residues of soybean/safflower, and application of farmyard manure (FYM) at 6 Mg (t) ha -1 alone or in combination with 20 kg N and 13 kg P ha -1 supplied through chemical fertilizers or comparatively higher dose of chemical fertilizer (60 kg N and 35 kg P ha -1) either maintained or increased the SOC stock. However, the combination of FYM and chemical fertilizer increased the profile SOC stock (69.9 Mg ha -1), overall SOC build up (37.1%) and also sequestered high amount of SOC (11.9 Mg C ha -1 or 0.79 Mg C ha -1 yr -1) compared with control and chemical fertilizer alone. Higher grain yield (2.10 and 1.49 Mg ha -1 of soybean and safflower, respectively) was obtained through the application of FYM at 6 Mg ha -1+N 20P 13. For every Mg C ha -1 increase in the root zone, there was 0.145 and 0.059 Mg ha -1 increase in grain yield of soybean and safflower, respectively. Stabilization of the SOC stock requires a minimum input of 3.47 Mg C ha -1 yr -1. Application of 40 kg N+26 kg P ha -1 through chemical fertilizer also maintained the SOC stock at the antecedent level based on the SOC stocks in 1992. Therefore, the combined use of organic manure (crop residues and FYM) along with chemical fertilizer is essential to enhancing the SOC sequestration in a soybean-safflower sequence under rainfed conditions on Vertisols in central India.