Stabilizing steep slopes with soil conditioners and plants

The approach in this study of runoff and erosion control on steep slopes was to combine soil stabilizers with the planting of drought-resistant, perennial plants.The effect of 10 t ha⁻¹ phosphogypsum (PG) + 70 kg ha⁻¹ polysaccharide (PS), 10 t ha⁻¹ PG and 20 kg ha⁻¹ polyacrylamide (PAM), and 200 kg ha⁻¹ PS on the erosion of steep slopes (30–60%) was studied in plots 2 m in width and of different lengths (12–20 m), at three of different sites in Israel (semiarid conditions), and under natural rainfall conditions. Likewise, observations on the establishment and development of nonirrigated, drought-resistant, perennial plants on steep slopes (40–60%), combined with 10 t ha⁻¹ PG + 70 kg ha⁻¹ PS, were conducted at two sites in Israel.PS + PG and PAM + PG treatments were very efficient in erosion control in a wide range of soil types, ESP, CaCO₃ level, and weather conditions. These treatments reduced erosion six- to eleven-fold in comparison with the control. No significant difference was found between PS + PG and PAM + PG treatments. However, the application of PAM was problematic due to its very low dissulution rate and its high viscosity in water. Two-hundred kg PS without PG was found efficient only at one experimental site with calcic haploxeralf soil and 300 mm average annual rainfall.The combination of PS + PG, and drought-resistant, perennial plants was very sucessful. The plants developed very well without irrigation throughout the long, dry summer. Only one year later, the creeper plant canopy covered an area of 0.75–1.5 m, and the bushes were 0.8–1.2 m in height.     

Strategies to optimize nitrogen efficiency when fertilizing with pig slurries in dryland agricultural systems

In dryland agricultural systems, pig slurry (PS) is usually applied to cereal crops only at sowing, and slurries accumulate for the rest of the year in pits. In this context, a four-year experiment was established in order to evaluate the feasibility of PS applications at the barley or wheat tillering stage. The main treatments were PS either applied at sowing (25 Mg ha⁻¹) or not, but they alternated after a two-year period. Both were annually combined with eight side-dressing treatments at cereal tillering: mineral N as NH₄NO₃ (M; 60 or 120 kg N ha⁻¹ yr⁻¹), PS from fattening pigs (PSf; 17, 30, 54 Mg ha⁻¹ yr⁻¹), PS from sows (PSs; 25, 45, 81 Mg ha⁻¹ yr⁻¹) and a treatment without N. The combined fertilization treatments were 18 plus a control (no N applied). In the context of crop rotation, the biennial alternation of PS applied at sowing allowed the control of soil nitrate increments, while PS side-dressing improved N recovery compared with a unique application at sowing. The highest yields (>3.6 Mg ha⁻¹ yr⁻¹) were obtained with an annual average (4-yr) N rate close to 173 kg N ha⁻¹ (±40 kg N ha⁻¹). The best overall strategies corresponded to PSs side-dressings of 50–90 kg N ha⁻¹. These PSs rates also recorded the highest values on the five calculated N-efficiency indexes, which were higher than or similar to results from M side-dressings or those recorded in the literature. These similarities (M vs. PSs) were also shown by the reduction of unaccounted-for N inside the overall N balance. Thus, split PS application during the crop cycle is a sound fertilization option in dryland systems.     

Soil loss from road batters in the Karuah state forest,Eastern Australia

Open plot sediment traps 0.8 m wide recorded flux rates up to 56 kg y⁻¹ mwidth⁻¹ for cut batters and 3.2 kg y⁻¹ mwidth⁻¹ for fill batters. The rates for cut batters were ten times higher than the sediment flux rates for hillslopes above them. The actual erosion rates for cut batters and fill batters are probably 100 times and 10 times respectively larger than those for the natural hillslopes. The erosion rates are significantly correlated to batter height and slope; positively correlated for cut batters and negatively correlated for fill batters. The rate of erosion of batters decreases exponentially over time.     

Comparative assessment of maize,finger millet and sorghum for household food security in the face of increasing climatic risk

Questions as to which crop to grow, where, when and with what management, will be increasingly challenging for farmers in the face of a changing climate. The objective of this study was to evaluate emergence, yield and financial benefits of maize, finger millet and sorghum, planted at different dates and managed with variable soil nutrient inputs in order to develop adaptation options for stabilizing food production and income for smallholder households in the face of climate change and variability. Field experiments with maize, finger millet and sorghum were conducted in farmers’ fields in Makoni and Hwedza districts in eastern Zimbabwe for three seasons: 2009/10, 2010/11 and 2011/12. Three fertilization rates: high (90 kg N ha⁻¹, 26 kg P ha⁻¹, 7 t ha⁻¹ manure), low (35 kg N ha⁻¹, 14 kg P ha⁻¹, 3 t ha⁻¹ manure) and a control (zero fertilization); and three planting dates: early, normal and late, were compared. Crop emergence for the unfertilized finger millet and sorghum was <15% compared with >70% for the fertilized treatments. In contrast, the emergence for maize (a medium-maturity hybrid cultivar, SC635), was >80% regardless of the amount of fertilizer applied. Maize yield was greater than that of finger millet and sorghum, also in the season (2010/11) which had poor rainfall distribution. Maize yielded 5.4 t ha⁻¹ compared with 3.1 t ha⁻¹ for finger millet and 3.3 t ha⁻¹ for sorghum for the early plantings in the 2009/10 rainfall season in Makoni, a site with relatively fertile soils. In the poorer 2010/11 season, early planted maize yielded 2.4 t ha⁻¹, against 1.6 t ha⁻¹ for finger millet and 0.4 t ha⁻¹ for sorghum in Makoni. Similar yield trends were observed on the nutrient-depleted soils in Hwedza, although yields were less than those observed in Makoni. All crops yielded significantly more with increasing rates of fertilization when planting was done early or in what farmers considered the ‘normal window’. Crops planted early or during the normal planting window gave comparable yields that were greater than yields of late-planted crops. Water productivity for each crop planted early or during the normal window increased with increase in the amount of fertilizer applied, but differed between crop type. Maize had the highest water productivity (8.0 kg dry matter mm⁻¹ ha⁻¹) followed by sorghum (4.9 kg mm⁻¹ ha⁻¹) and then finger millet (4.6 kg mm⁻¹ ha⁻¹) when a high fertilizer rate was applied to the early-planted crop. Marginal rates of return for maize production were greater for the high fertilization rate (>50%) than for the low rate (<50%). However, the financial returns for finger millet were more attractive for the low fertilization rate (>100%) than for the high rate (<100%). Although maize yield was greater compared with finger millet, the latter had a higher content of calcium and can be stored for up to five years. The superiority of maize, in terms of yields, over finger millet and sorghum, suggests that the recommendation to substitute maize with small grains may not be a robust option for adaptation to increased temperatures and more frequent droughts likely to be experienced in Zimbabwe and other parts of southern Africa.     

Winter Wheat Cultivar Responses to Fungicide Application are Affected by Nitrogen Fertilization Rate

Foliar fungicides are important management inputs for winter wheat (Triticum aestivum L.) in high-yielding areas of Europe, but their effectiveness may interact with cultivar selection and nitrogen (N) fertilization. No information is available on the potential use of fungicides in reducing yield losses from foliar diseases in Croatia, where wheat crop is extensively grown under low N inputs. Field experiments were conducted during 2000–02 to evaluate the agronomic responses of six winter wheat cultivars to fungicide application (tebuconazol around heading) compared with untreated plots at low (67 kg N ha⁻¹) and high (194 kg N ha⁻¹) N fertilization rates. Grain yields tended to increase in all years following fungicide treatment at high N rate by an average of 10.1 % (773 kg ha⁻¹), but improved significantly in one year only at low N rate. When these occurred, yield increases were associated with larger grain weight per ear primarily due to heavier 1000-kernel weight. Cultivars differed in their responses to fungicide application across growing seasons and N fertilization rates. Under low disease pressure in 2000 and 2001, improved yields with fungicide use occurred for few susceptible cultivars only, whereas all cultivars significantly increased yields under higher disease severity in 2002 by an average of 383 kg ha⁻¹ (5.0 %) at low N rate and 1443 kg ha⁻¹ (19.0 %) at high N rate. Following fungicide application at high N rate, some susceptible cultivars outyielded resistant cultivars, whereas opposite responses occurred in untreated plots. High N fertilization rate consistently produced larger grain yields except under high disease severity and no fungicide sprayed in 2002, when it had no benefits at all over low N rate. Fungicide application showed limited importance for wheat performance at low N rate; however, cultivars significantly differed in yield responses as well as in rankings after fungicide use at high N fertilization rate.     

Improving the productivity and profitability of irrigated rice production in Mauritania

Yield, input use, productivity and profitability of irrigated rice in Mauritania were analyzed during the 1997 wet season (July–December) in the Senegal river delta and middle valley, in collaboration with 42 large farmers and extension staff. Objectives were to determine agronomic constraints to rice cropping and to evaluate alternative crop management strategies aimed at overcoming these constraints. Grain yields ranged from 0.9 to 8.5 t ha⁻¹ and averaged 4.4 t ha⁻¹. Based on crop simulations, average yield potential in farmers' fields was estimated at 8.6 t ha⁻¹, indicating considerable scope for increased yields. Our survey identified the following main agronomic constraints: (i) mismatches between timing of nitrogen (N) fertilizer applications and critical N demanding growth stages of the rice plant; (ii) non-use of phosphorus (P) fertilizer on P deficient soils; (iii) largely neglected or inefficient weed management and (iv) late harvesting, often due to non-availability of combine harvesters. Based on these results we tested improved nutrient and weed management practices with farmers during the 1998 wet season. Improved nutrient management (i.e. T1: application of 20 kg P ha⁻¹ and 150 kg N ha⁻¹ in three splits at start tillering, panicle initiation and booting) increased yields by 0.9 t ha⁻¹. Improved weed management (i.e. T2: application of 6.0 L propanil ha⁻¹ and 2.0 L 2,4-d-amine ha⁻¹ at 2–3 leaf stage of weeds) also raised yields by 0.9 t ha⁻¹ as compared to farmers' practice (TP). The combined effect of T1 and T2 (i.e. T3) was additive: improving both nutrient and weed management raised yields by 1.8 t ha⁻¹ over average farmers’ yields of 3.9 t ha⁻¹, i.e. an increase of almost 50%. The improved crop management practices were highly profitable: compared to farmers’ practice, net benefits increased by 40% for T1 and T2 and by about 85% for T3, with minimal additive investments. Inputs used for T3 are relatively easily available in Mauritania. We concluded that increased farmer awareness of the profitability of improved nutrient and weed management may have a tremendous impact on the competitiveness of rice production in Mauritania     

Explaining rice yields and yield gaps in Central Luzon,Philippines: An application of stochastic frontier analysis and crop modelling

Explaining yield gaps is crucial to understand the main technical constraints faced by farmers to increase land productivity. The objective of this study is to decompose the yield gap into efficiency, resource and technology yield gaps for irrigated lowland rice-based farming systems in Central Luzon, Philippines, and to explain those yield gaps using data related to crop management, biophysical constraints and available technologies.Stochastic frontier analysis was used to quantify and explain the efficiency and resource yield gaps and a crop growth model (ORYZA v3) was used to compute the technology yield gap. We combined these two methodologies into a theoretical framework to explain rice yield gaps in farmers’ fields included in the Central Luzon Loop Survey, an unbalanced panel dataset of about 100 households, collected every four to five years during the period 1966–2012.The mean yield gap estimated for the period 1979–2012 was 3.2 ton ha⁻¹ in the wet season (WS) and 4.8 ton ha⁻¹ in the dry season (DS). An average efficiency yield gap of 1.3 ton ha⁻¹ was estimated and partly explained by untimely application of mineral fertilizers and biotic control factors. The mean resource yield gap was small in both seasons but somewhat larger in the DS (1.3 ton ha⁻¹) than in the WS (1.0 ton ha⁻¹). This can be partly explained by the greater N, P and K use in the highest yielding fields than in lowest yielding fields which was observed in the DS but not in the WS. The technology yield gap was on average less than 1.0 ton ha⁻¹ during the WS prior to 2003 and ca. 1.6 ton ha⁻¹ from 2003 to 2012 while in the DS it has been consistently large with a mean of 2.2 ton ha⁻¹. Varietal shift and sub-optimal application of inputs (e.g. quantity of irrigation water and N) are the most plausible explanations for this yield gap during the WS and DS, respectively.We conclude that the technology yield gap explains nearly half of the difference between potential and actual yields while the efficiency and resource yield gaps explain each a quarter of that difference in the DS. As for the WS, particular attention should be given to the efficiency yield gap which, although decreasing with time, still accounted for nearly 40% of the overall yield gap.     

Production and consumption of tropical seagrass fields in Eastern Indonesia measured with bell jars and microelectrodes

During the Indonesian-Dutch Snellius-II Expedition the production and consumption of tropical seagrass species were measured with bell jars at four sampling stations in eastern Indonesia. Applying a conversion factor of 0.29, the amount of carbon fixed and mineralized was calculated from the recorded oxygen evolution. The gross production of the different seagrass communities was found to be between 1230 and 4700 mg C·m⁻²·d⁻¹. The consumption lay between 860 and 3860 mg C·m⁻²·d⁻¹. From these data a relatively low net production of 60 to 1060 mg C·m⁻²·⁻¹ could be calculated. At one sampling station incubations were carried out at different depths in a sloping Halodule uninervis (Forssk.) Aschers meadow, which indicated that seagrasses above a depth of about 2 m may become subject to photoinhibition. A linear correlation between biomass and measured production was found for Thalassia hemprichii (Ehrenb.) Aschers. Above a biomass of 100 g DW·m⁻² the production per unit of biomass decreased due to self shading.Using microelectrodes the oxygen production of epiphytes was found to be 230 mg C·m⁻² leaf surface·d⁻¹. at 1900 μE·m⁻²·s⁻¹ assuming an epiphyte coverage of 40%. This indicated that up to 36% of the primary production in a seagrass community may be attributed to epiphytes.The seagrass fields in Indonesia were found to be healthy ecosystems with a high primary production, but organisms within the communities use the abundance of organic matter very efficiently, creating net production rates of 100 to 300 mg C·m⁻²·d⁻¹ which are similar to barren areas.     

Fertilizers,hybrids, and the sustainable intensification of maize systems in the rainfed mid-hills of Nepal

In the rainfed mid-hill region of Nepal, most fields receive 2–3 t ha⁻¹ of organic compost application every year. Despite efficient recovery and use of organics in the mixed crop-animal systems that predominant in the mid-hills, depleted soil fertility is widely understood to be a significant constraint to crop productivity, with most farmers achieving maize grain yields below 2 t ha⁻¹. Increased use of fertilizer may arrest and even reverse long-term soil quality degradation, but few farmers in the mid-hills use them at present and existing recommendations are insufficiently responsive to site, varietal, and management factors that influence the productivity and profitability of increased fertilizer use. Moreover, policy makers and development practitioners often hold the perception that returns to fertilizer use in the mid-hills are too low to merit investment. In this study, on-farm experiments were conducted at 16 sites in the Palpa district, Nepal to assess the responsiveness of a maize hybrid (DKC 9081) and an ‘improved’ open-pollinated maize variety (‘OPV’, Manakamana-3) to four nitrogen (N) rates, i.e., 0, 60, 120 and 180 kg ha⁻¹, with each N rate response evaluated at 30:30 and 60:60 kg ha⁻¹ rates of phosphorus (P₂O₅) and potassium (K₂O), respectively. With sound agronomy and high rates of fertilizer (180:60:60 kg N:P₂O₅:K₂O ha⁻¹), grain yields observed in the field experiments exceeded 8 t ha⁻¹ with hybrids and 6 t ha⁻¹ with OPV. Yield levels were lower for OPV than hybrid at every level of applied N, but both genotypes responded linearly to N with partial factor productivity for N (PFP_N) ranging from 14 to 19 for OPV versus 26–30 for hybrid, with improved N efficiencies obtained when P and K rates were significantly higher. Averaged across phosphorus (P) and potassium (K) levels, a $ 1 incremental investment in fertilizer increased the gross margin (GM) by $ 1.70 ha⁻¹ in OPV and by $ 1.83 ha⁻¹ in the hybrid. For the full response of N, requires higher rate of P₂O₅:K₂O and vice-versa and full response to P₂O₅:K₂O does not occur if N is absent. These results suggest that, i) degraded soils in the mid-hills of Nepal respond favorably to macronutrient fertilizers – even at high rates, ii) balanced fertilization is necessary to optimize returns on investments in N but must be weighed against additional costs, iii) OPVs benefit from investments in fertilizer, albeit at a PFP_N that is 36–47% lower than for hybrids, and, consequently iv) hybrids are an effective mechanism for achieving a higher return on fertilizer investments, even when modest rates are applied. To extend these findings across years and sites in the mid-hills, crop growth simulations using the CERES-maize model (DSSAT) were conducted for 11 districts with historical weather and representative soils data. Average simulated (hybrid) maize yields with high fertilizer rate (180:60:60 kg N:P₂O₅:K₂O ha⁻¹) ranged from 3.9 t ha⁻¹ to 7.5 t ha⁻¹ across districts, indicating a high disparity in attainable yield potential. By using these values to estimate district-specific attainable yield targets, recommended N fertilizer rates vary between 65 and 208 kg N ha⁻¹, highlighting the importance of developing domain-specific recommendations. Simulations also suggest the potential utility of using weather forecasts in tandem with site and planting date information to adjust fertilizer recommendations on a seasonal basis.     

Evaluation of long-term conservation agriculture and crop intensification in rice-wheat rotation of Indo-Gangetic Plains of South Asia: Carbon dynamics and productivity

In the context of deteriorating soil health, stagnation of yield in rice-wheat cropping system (RWCS) across Indo- Gangetic plains (IGP) and environmental pollution, a long term field experiment was conducted during 2009–2016 taking four crop scenarios with conservation agriculture (CA), crop intensification and diversified cropping as intervening technology aiming to evaluate the sustainability of the systems. Scenario 1 (S1) represented conventional farmers’ practice of growing rice and wheat with summer fallow. In scenario 2 (S2) and scenario 3 (S3), legume crop was taken along with rice and wheat with partial CA and full CA, respectively. Conventional RWCS was replaced with rice-potato + maize- cowpea cropping system with partial CA in scenario 4 (S4). The S3 scenario registered highest total organic carbon (TOC) stock of 47.71 Mg C ha⁻¹ and resulted in significant increase of 14.57% over S1 (Farmer’s practice) in 0–30 cm soil depth after 7 years of field trial. The S4 scenario having intensified cropping systems recorded lowest TOC of 39.33 Mg C ha⁻¹ and resulted in significant depletion of 17.56% in C stock with respect to S3 in 0–30 cm soil depth. The TOC enrichment was higher in S2, S3 and S4 scenario in the surface soil (0–10 cm) compared to S1. At lower depth (20–30 cm), the TOC enrichment was significantly higher in S2 (12.82 Mg C ha⁻¹) and S3 (13.10 Mg C ha⁻¹ soil) over S1 scenario. The S2 and S3 scenario recorded highest increased allocation of TOC (3.55 and 6.13 Mg C ha⁻¹) to passive pool over S1. The S2 (15.72 t ha⁻¹), S3 (16.08 t ha⁻¹) and S4 (16.39 t ha⁻¹) scenarios recorded significantly higher system rice equivalent yield over S1 (10.30 t ha⁻¹). Among the scenarios, S3 scenario had greater amount of total soil organic carbon, passive pool of carbon and higher system rice equivalent yield, thus, is considered the best cropping management practice to maintain soil health and food security in the middle IGP.     

Temporal and lateral fluctuations in production and biomass of bacterioplankton in the western Dutch Wadden Sea

To contribute to the validation of a recently developed ecosystem model of the western Wadden Sea (EON, 1988), data on bacterial biomass and production were acquired. Seven field stations, spread over the two main basins of the estuarine system, were sampled monthly in 1986. Between these basins significant differences were found in counts, biovolume, biomass and production of bacteria (measured by the ³H-thymidine method) with consistently higher mean values of bacterial variables in the Vlie basin. Bacterial production rates of 2 to 175 mg C· m⁻³· d⁻¹ were obtained for the Vlie basin, with an annual production of 10 to 11 g C· m⁻³, while the production in the Marsdiep basin did not exceed 45 mg C·m⁻³ ·d⁻¹, with an annual production of g C·m⁻³. Bacterial biomass varied over the year from 2 to 140 mg C·m⁻³ in the study area, with a mean biomass of 39 mg C·m⁻³ in the Vlie basin and 23 mg C·m⁻³ in the Marsdiep basin. Blooms of bacteria occurred in May and July–August. Spatial and temporal fluctuations in bacterial variables are discussed, taking into account different environmental factors and the availability of food for bacteria in relation to transport and exchange of water masses between the two basins and the North Sea. Results are compared with the results as simulated by the ecosystem model.     

Growth and yield of winter wheat in the first 3 years of a monoculture under varying N fertilization in NW Germany

Different preceding crops interact with almost all husbandry and have a major effect on crop yields. In order to quantify the yield response of winter wheat, a field trial with different preceding crop combinations (oilseed rape (OSR)–OSR–OSR–wheat–wheat–wheat), two sowing dates (mid/end of September, mid/end of October) and 16 mineral nitrogen (N) treatments (80–320 kg N ha⁻¹) during 1993/1994–1998/1999, was carried out at Hohenschulen Experimental Station near Kiel in NW Germany. Single plant biomass, tiller numbers m⁻², biomass m⁻², grain yield and yield components at harvest were investigated. During the growing season, the incidence of root rot (Gaeumannomyces graminis) was observed. Additionally, a bioassay with Lemna minor was used to identify the presence of allelochemicals in the soil after different preceding crops.Averaged over all years and all other treatments, wheat following OSR achieved nearly 9.5 t ha⁻¹, whereas the second wheat crop following wheat yielded about 0.9 t ha⁻¹ and the third wheat crop following 2 years of wheat about 1.9 t ha⁻¹ less compared with wheat after OSR. A delay of the sowing date only marginally decreased grain yield by 0.2 t ha⁻¹. Nitrogen fertilization increased grain yield after all preceding crop combinations, but at different levels. Wheat grown after OSR reached its maximum yield of 9.7 t ha⁻¹ with 210 kg N ha⁻¹. The third wheat crop required a N amount of 270 kg N ha⁻¹ to achieve its yield maximum of 8.0 t ha⁻¹.Yield losses were mainly caused by a lower ear density and a reduced thousand grain weight. About 4 weeks after plant establishment, single wheat plants following OSR accumulated more biomass compared to plants grown after wheat. Plants from the third wheat crop were smallest. This range of the preceding crop combinations was similar at all sampling dates throughout the growing season.Root rot occurred only at a low level and was excluded to cause the yield losses. The Lemna bioassay suggested the presence of allelochemicals, which might have been one reason for the poor single plant development in autumn.An increased N fertilization compensated for the lower number of ears m⁻² and partly reduced the yield losses due to the unfavorable preceding crop combination. However, it was not possible to completely compensate for the detrimental influences of an unfavorable preceding crop on the grain yield of the subsequent wheat crop.     

Restoration of eroded soil with conservation tillage

Eroded Kandhapludult soils occupy more than 40% of the Southern Piedmont region of the USA. The humid-thermic climate associated with the Ultisols permits double crop residue production ranging from 10 to 14 Mg ha⁻¹ yr⁻¹. Long-term conservation tillage into these crop residues is beneficial in ameliorating the effects of soil erosion. During the course of a five-year study, decomposition of these residues increased soil carbon significantly. Restoration processes were initiated by increasing average soil carbon, representing slight, moderate and severe soil erosion classes, from 0.97 to 2.37% in the 0 to 1.5-cm depth. Accompanying soil carbon responses were increases in soil N, water-stable aggregation and infiltration. Runoff coefficients on conservation tilled restored soils was only 6%, compared to 35% for those conventionally tilled. Rill and interrill soil loss rates were also reduced significantly with surface residue provided with conservation tillage.Restoring Ultisol landscapes with variable levels of soil erosion requires differential fertilization. All fertilizer requirements for severely eroded plots were 1.43 to 2.30-fold higher than those of moderately eroded plots. Because biological N fixation by the crimson clover (Trifolium incarnatum L.) cover crop appeared to be retarded on the severely eroded site, observed plant N stress developed on the irrigated/conservation tillage treatment. Cumulative grain yields of severely eroded site, ranged from 15.4 to 30.3 Mg ha⁻¹ 5yr⁻¹, and were statistically equal to or exceeded those of the slightly eroded site. Conservation tillage grain yields were best optimized on the rainfed-moderately eroded site, probably because of the more desirable texture-organic properties of the 13-cm thick Ap horizon. Management of cool-season cover crops with conservation tillage appears essential to restore and sustain crop productivity on eroded Ultisols.     

Tillage,cover crops,and nitrogen fertilization effects on soil nitrogen and cotton and sorghum yields

Sustainable soil and crop management practices that reduce soil erosion and nitrogen (N) leaching, conserve soil organic matter, and optimize cotton and sorghum yields still remain a challenge. We examined the influence of three tillage practices (no-till, strip till and chisel till), four cover crops {legume [hairy vetch (Vicia villosa Roth)], nonlegume [rye (Secaele cereale L.)], vetch/rye biculture and winter weeds or no cover crop}, and three N fertilization rates (0, 60–65 and 120–130 kg N ha⁻¹) on soil inorganic N content at the 0–30 cm depth and yields and N uptake of cotton (Gossypium hirsutum L.) and sorghum [Sorghum bicolor (L.) Moench]. A field experiment was conducted on Dothan sandy loam (fine-loamy, siliceous, thermic, Plinthic Paleudults) from 1999 to 2002 in Georgia, USA. Nitrogen supplied by cover crops was greater with vetch and vetch/rye biculture than with rye and weeds. Soil inorganic N at the 0–10 and 10–30 cm depths increased with increasing N rate and were greater with vetch than with rye and weeds in April 2000 and 2002. Inorganic N at 0–10 cm was also greater with vetch than with rye in no-till, greater with vetch/rye than with rye and weeds in strip till, and greater with vetch than with rye and weeds in chisel till. In 2000, cotton lint yield and N uptake were greater in no-till with rye or 60 kg N ha⁻¹ than in other treatments, but biomass (stems + leaves) yield and N uptake were greater with vetch and vetch/rye than with rye or weeds, and greater with 60 and 120 than with 0 kg N ha⁻¹. In 2001, sorghum grain yield, biomass yield, and N uptake were greater in strip till and chisel till than in no-till, and greater in vetch and vetch/rye with or without N than in rye and weeds with 0 or 65 kg N ha⁻¹. In 2002, cotton lint yield and N uptake were greater in chisel till, rye and weeds with 0 or 60 kg N ha⁻¹ than in other treatments, but biomass N uptake was greater in vetch/rye with 60 kg N ha⁻¹ than in rye and weeds with 0 or 60 kg N ha⁻¹. Increased N supplied by hairy vetch or 120–130 kg N ha⁻¹ increased soil N availability, sorghum grain yield, cotton and sorghum biomass yields, and N uptake but decreased cotton lint yield and lint N uptake compared with rye, weeds or 0 kg N ha⁻¹. Cotton and sorghum yields and N uptake can be optimized and potentials for soil erosion and N leaching can be reduced by using conservation tillage, such as no-till or strip till, with vetch/rye biculture cover crop and 60–65 kg N ha⁻¹. The results can be applied in regions where cover crops can be grown in the winter to reduce soil erosion and N leaching and where tillage intensity and N fertilization rates can be minimized to reduce the costs of energy requirement for tillage and N fertilization while optimizing crop production.     

Polysaccharide and salt effects on infiltration and soil erosion. A rainfall simulation study

Seals forming at the soil surface during rainstorms reduce water penetration and increase runoff in many arid and semi-arid regions. The effect of surface application of an anionic polysaccharide (designated F-Ac), synthesized by the filamentous cyanobacterium Anabaenopsis circularis PCC 6720, on infiltration rate (IR), runoff and erosion of three soils during simulated rainstorms, was studied. The interaction between F-Ac and electrolyte concentration at the soil surface was studied by using distilled water (DW) or tap water (TW) or by spreading phosphogypsum (PG) on the soil surface. F-Ac added at the rate of 3.4 kg ha⁻¹ together with PG at the rate of 5 t ha⁻¹ was the most efficient treatment in improving infiltration and reducing runoff and erosion. This treatment reduced runoff, from the three soils studied, from 65–80% in the control to 14–24%. Soil loss was reduced from 3.6–4.5 Mg ha⁻¹ in the control to 0.5–1.3 Mg ha⁻¹ in the treated soils. DW treatment, singly and in combination with F-Ac, was quite inefficient in preventing seal formation and in reducing runoff and soil loss. Adding F-Ac with TW maintained final IR and runoff levels intermediate between those of F-Ac with PG and those of F-Ac with DW. Electrolytes in the soil surface which flocculated soil clay, enhanced the beneficial effect of F-Ac on aggregate stability and thus greatly reduced water and soil losses. The efficacy of F-Ac as a stabilizing agent (i.e., soil conditioner) wore out during three consecutive storms of 60 mm each.     

Managing Tephrosia mulch and fertilizer to enhance coffee productivity on smallholder farms in the Eastern African Highlands

In Maraba, Southwest Rwanda, coffee productivity is constrained by poor soil fertility and lack of organic mulch. We investigated the potential to produce mulch by growing Tephrosia vogelii either intercropped with smallholder coffee or in arable fields outside the coffee, and the effect of the mulch on coffee yields over two years. Two accessions of T. vogelii (ex. Gisagara, Rwanda and ex. Kisumu, Kenya) were grown for six months both within and outside smallholder coffee fields in the first year. Experimental blocks were replicated across eight smallholder farms, only a single replicate per farm due to the small farm sizes. The accession from Rwanda (T. vogelii ex. Gisagara) grew more vigorously in all experiments. Soils within the coffee fields were more fertile those outside the coffee fields, presumably due to farmers’ long-term management with mulch. Tephrosia grew less well in the fields outside coffee, producing only 0.6–0.7 Mg ha⁻¹ of biomass and adding (in kg ha⁻¹) 19 N, 1 P and 6 K in the mulch. By contrast, Tephrosia intercropped with coffee, produced 1.4–1.9 Mg ha⁻¹ of biomass and added (in kg ha⁻¹) 42–57 N, 3 P and 13–16 K in the mulch. Coffee yields were increased significantly by 400–500 kg ha⁻¹ only in the treatments where Tephrosia was intercropped with coffee. Soil analysis and a missing-nutrient pot experiment showed that the poor growth of Tephrosia in the fields outside coffee was due to soil acidity (aluminium toxicity) combined with deficiencies of P, K and Ca.In the second year, the treatments in fields outside coffee were discontinued, and in the coffee intercrops, two Tephrosia accessions were grown in treatments with and without NPK fertilizer. Tephrosia grew well and produced between 2.5 and 3.8 Mg ha⁻¹ biomass for the two accessions when interplanted within coffee fields, adding 103–150 kg N ha⁻¹, 5–9 kg P ha⁻¹ and 24–38 kg K ha⁻¹. Tephrosia mulch increased yields of coffee by 400 kg ha⁻¹. Combined use of NPK + Tephrosia mulch increased Tephrosia biomass production and in turn yielded an additional 300–700 kg ha⁻¹ of coffee. Over the two years, this was equivalent to a 23–36% increase in coffee yield using Tephrosia intercropping alone and a further 25–42% increase in coffee yield when NPK fertilizer was also added. Agronomic efficiency (AE) of nutrients added were 30% greater when the Tephrosia mulch was grown in situ and the two cultivars of Tephrosia did not differ in AE. The AE of Tephrosia mulch was 87% that of NPK fertilizer, reflecting the rapid mineralization of Tephrosia mulch. There was a synergistic effect of Tephrosia mulch on the efficiency with which NPK fertilizer was used by coffee. The increase in coffee yields was positively related to the amount of nutrients added in the Tephrosia biomass. Tephrosia intercropping required 30 man-days ha⁻¹ less than current farmer management due to reduced labour required for weeding, and benefit–cost ratios ranged between 3.4 and 5.5. The Tephrosia-coffee intercropping system offers great potential for agroecological intensification for smallholder farmers in the East African highlands.     

Effect of soil-N and urine-N on nitrate leaching under pure grass,pure clover and mixed grass/clover swards

During six annual drainage periods (DP_O to DP₅), the drainage water, the NO₃ concentration of the drainage water and the total leached N were compared under bare soils and under ryegrass/white clover, pure ryegrass and pure white clover stands in 80 deep lysimeters with 3m² area. For each soil cover, the sensitivity of the variables to the soil N supplying capacity at sowing was measured, using a set up of 32 lysimeters. This initial capacity to supply mineral N (SoilN) varied from 90 to 230 kg N ha⁻¹ year⁻¹. The stands were managed in a simulated rotational grazing system, without addition of fertilizer N. During the first drainage period after sowing (DP₀), N leaching increased significantly with the initial SoilN under the bare soils, the pure grass and the mixture, but was not influenced under the pure clover. In the following drainage periods, N leaching increased according to the sequence pure grass (1–5 kg N ha⁻¹ year⁻¹), mixed swards (1–19 kg N), pure white clover (28–140 kg N) and bare soils (84–149 kgN ha⁻¹ year⁻¹). It was only slightly greater under the mixture than under the pure grass, despite the N harvest and the N animal returns were much higher. Under the mixed stands, N leaching became independent of the initial SoilN in DP₁ and DP₂ and decreased with increasing initial SoilN in DP₃, DP₄ and DP₅. This inversion of the SoilN effect in time and the limited amounts of leached N demonstrated that adaptations in the ecosystem tend to counteract the SoilN effect on the N losses. In the mixed stands, the accumulated N leaching represented 12 and 21% of the accumulated N at harvest for the initially rich and poor soils, respectively and 32% of the accumulated N harvest in the mixed clover, whatever the initial SoilN. N leaching also represented 13% of the urine-N above 80 kgN ha⁻¹ year⁻¹. The low values of N leaching under the mixed swards make them sustainable for environment quality. Mechanisms which regulate the N fluxes are discussed, using published data on the soil and some results concerning the harvests in the same experiment.     

江苏机插水稻大面积均衡增产共性特征分析

以江苏26个水稻高产创建示范县为对象,对水稻田产量及群体结构的典型田块进行调查。将水稻生产要素(种植方、品种、播期、种植方式)类型相近或相同的田块按产量分成高产田(I,> 10.5 t hm^-2)、中产田(II,9.0 ~10.5 t hm^-2)、低产田(III,< 9.0 t hm^-2) 3个等级,比较其产量结构、空间分布均衡性等群体指标。结果表明：(1)高产田的颖花数、穗数、穗粒数均有显著优势;不同类型田块在行距、穴距、单位面积穴数等空间配置上差异未达显著水平。(2)不同产量水平田块单穴穗数整齐度差异显著;产量与单穴穗数整齐度呈极显著正相关(r=0.436^**,2009;r=0.441^**,2010)。(3)顶部叶片长度增加有利于总粒数的增加,但易降低结实率,尤其是下位叶。表明提高单穴穗数整齐度和穗粒数整齐度,是协调水稻穗数、穗粒数和粒重三者矛盾的有效途径;也是江苏大面积均衡增产的有效途径。     

Appropriate seeding rate for einkorn,emmer, and spelt grown under rainfed condition in southern Italy

Einkorn (Triticum monococcum L.), emmer (Triticum dicoccum Schübler) and spelt (T. spelta L.) are still cultivated in Italy. These three hulled wheat species are more commonly known as “Farro”. Little is known about agronomic practices that optimise the grain yield of these species.This study has been carried out to establish the appropriate seeding rate for einkorn, emmer and spelt which is grown in southern Italy (Apulia region), a typical Mediterranean environment, where durum wheat is principally cultivated. Two years of experimental field trials were conducted with three seeding rates (100, 150 and 200 viable seeds per square meter).Emmer had the highest hulled grain yield (3.54 t ha⁻¹) followed by spelt (2.80 t ha⁻¹) and einkorn (1.42 t ha⁻¹). Emmer also had a higher kernel weight and was heading earlier than the other species. The bad performance of einkorn can be accountable to the excessive time to reach heading and the natural inclination of plants to lodge, factors that reduce the ability of plant to complete grain ripening, resulting in light and shrivelled kernels. The lower grain yield of spelt in comparison to emmer may be due to later heading.Emmer and spelt performed the best when they were sown at 200 seeds m⁻² (3.85 and 3.09 t ha⁻¹, respectively). In contrast, einkorn showed the highest grain yield (1.69 t ha⁻¹) at the lowest seeding rate (100 seeds m⁻²). Further, additional experimentation is required to confirm this.These results indicate that emmer is the most appropriate hulled wheat species for cropping under southern Italy’s growing conditions, and provide further information about the use of these species in the marginal area preservation or when the cultivation of economically profitable crops is precludes by water deficiency and soil poorness.