Influence of harvest time and frequency on light interception and biomass yield of festulolium and tall fescue cultivated on a peatland

In this study, we report efficiencies of light capture and biomass yield of festulolium and tall fescue cultivated on a riparian fen in Denmark under different harvesting managements. Green biomass targeted for biogas production was harvested either as two cuts (2C) or three cuts (3C) in a year. Three different timings of the first cut in the 2C systems were included as early (2C-early), middle (2C-mid) and late (2C-late) cuts corresponding to pre-heading, inflorescence emergence and flowering stages, respectively. The fraction of intercepted photosynthetically active radiation (f_PAR) was derived from the canopy reflectance measured on 61 dates throughout a year, and cumulative interception of PAR (IPAR) and radiation use efficiency (RUE) was calculated. The dynamics of f_PAR and biomass accumulations was similar for both crops before the first cuts in all managements. Festulolium f_PAR in 2C-early and 2C-mid managements declined faster than in 2C-late and 3C managements in the second growth period and thus growing period IPAR of 2C-early and 2C-mid declined by 8% as compared to 3C management where IPAR was 925 MJ m⁻². Annual festulolium dry matter (DM) yield in 2C-early and 2C-mid managements (average 14.1 Mg DM ha⁻¹) decreased by 22% compared to 3C management (18.2 Mg DM ha⁻¹). The highest and the lowest RUE of festulolium were observed in 3C and 2C-mid managements as 1.97 and 1.59 g MJ⁻¹, respectively. For tall fescue f_PAR declined rather slowly in the second growing period in all 2C managements, which contributed to similar IPAR (908–919 MJ m⁻²), total biomass yield (16.4–18.8 Mg DM ha⁻¹ yr⁻¹) and RUE (1.80–2.07 g MJ⁻¹) for all managements. Whereas both crops were highly productive under both 3C management and 2C management with first harvest after flowering (i.e., 2C-late), the 2C-late strategy is recommended as the least intensive of the two management systems.     

Response of giant reed (Arundo donax L.) to nitrogen fertilization and soil water availability in semi-arid Mediterranean environment

The aim of the present work was to evaluate the effect of soil water availability and nitrogen fertilization on yield, water use efficiency and agronomic nitrogen use efficiency of giant reed (Arundo donax L.) over four-year field experiment.After the year of establishment, three levels for each factor were studied in the following three years: I₀ (irrigation only during the year of establishment), I₁ (50% ETm restitution) and I₂ (100% ETm restitution); N₀ (0 kg N ha⁻¹), N₁ (60 kg N ha⁻¹) and N₂ (120 kg N ha⁻¹).Irrigation and nitrogen effects resulted significant for stem height and leaf area index (LAI) before senescence, while no differences were observed for stem density and LAI at harvest.Aboveground biomass dry matter (DM) yield increased following the year of establishment in all irrigation and N fertilization treatments. It was always the highest in I₂N₂ (18.3, 28.8 and 28.9 t DM ha⁻¹ at second, third and fourth year growing season, respectively). The lowest values were observed in I₀N₀ (11.0, 13.4 and 12.9 t DM ha⁻¹, respectively).Water use efficiency (WUE) was significantly higher in the most stressed irrigation treatment (I₀), decreasing in the intermediate (I₁) and further in the highest irrigation treatment (I₂). N fertilization lead to greater values of WUE in all irrigation treatment.The effect of N fertilization on agronomic nitrogen use efficiency (NUE) was significant only at the first and second growing season.Giant reed was able to uptake water at 160–180 cm soil depth when irrigation was applied, while up to 140–160 cm under water stress condition.Giant reed appeared to be particularly suited to semi-arid Mediterranean environments, showing high yields even in absence of agro-input supply.     

Development of critical nitrogen dilution curve in rice based on leaf dry matter

The critical nitrogen (N_c), defined as the minimum N concentration required for maximum growth, is proposed for diagnosis of the in-season N status in crop plants. It has been established for several crops including rice on whole-plant dry matter (DM) basis but has not been determined for canopy leaf basis. This research was undertaken to develop a new N_c dilution curve based on leaf dry matter (L_DM) and to assess its applicability to estimate the level of N nutrition for Japonica rice in east China. Three field experiments were conducted with varied N rates (0–360 kg N ha⁻¹) and three Japonica rice (Oryza sativa L.) hybrids, Lingxiangyou-18 (LXY-18), Wuxiangjing-14 (WXJ-14) and Wuyunjing (WYJ) in Jiangsu province of east China. Five hills from each plot were sampled from active tillering to heading for growth analysis and leaf N determination. The N_c dilution curve on leaf N concentration was described by the equation N_c = 3.76W^−0.218, when L_DM ranged from 0.67 to 4.25 t ha⁻¹. However, for L_DM < 0.67 t ha⁻¹, the constant critical value N_c = 4.09%L_DM was applied. This N_c dilution curve on L_DM basis was slightly higher than the curves on plant DM basis in Japonica rice, yet both lower than the reference curve of high yielding Indica rice in tropics. The N nutrition index (NNI) and accumulated N deficit (N_and) of leaves ranged from 0.65 to 1.06 and 79.62 to −6.39 kg ha⁻¹, respectively, during main growth stages under varied N rates in 2010 and 2011. The results indicate that the present N_c dilution curve and derived NNI and N_and adequately identified the situations of N-limiting and non-N-limiting nutrition in two rice varieties and could be used as reliable indicators of N status during growth of Japonica rice in east China.     

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.     

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.     

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.     

Alternative strategies for nitrogen fertilization of overwinter processing spinach (Spinacia oleracea L.) in Southern Italy

To identify the best practice for nitrogen (N) fertilization of overwinter processing spinach, two field experiments were carried out in the Foggia plain (Southern Italy), one of the most vocated area for leafy vegetables production. The field trials were aimed to define and suggest the proper fertilizer dose, typology and the right time of application. Experiment 1 evaluated four N fertilizer doses (0, 150, 225, 300 kg ha⁻¹) in a two-year field trial. Experiment 2 was aimed to assess the effect of the split distribution of prilled urea fertilizer in comparison with the application of nitrification inhibitor (DMPP) containing urea fertilizer, broadcasted at sowing.Spinach yield, yield quality (nitrate – NO₃⁻ – and carotenoids content), N-use efficiency and risk of soil nitrate (NO₃⁻-N) leaching were evaluated. The processing spinach yielded 37.8 and 3.6 t ha⁻¹ of fresh and dry yield, respectively (average of the two experiments). Fresh and dry yield among the fertilizing treatments were similar. Also the β-carotene and the lutein content of spinach leaves (19.5 and 38.1 mg kg⁻¹, respectively) were not affected by the N fertilizer dose. Conversely, the N dose strongly influenced the NO₃⁻ content of the leafy vegetable tissues (1286 mg kg⁻¹ on average, 58% lower than the limits imposed by the EC regulation). As expected, the different rainfall pattern influenced both the leaf NO₃⁻ content and the risk of soil NO₃⁻-N leaching. The results achieved demonstrated that, in order to get a favorable trade-off, among yield, yield quality, N-use efficiency and environmental impact, the processing spinach growers of the Foggia plain area should be encouraged to apply 225 kg N ha⁻¹ as maximum fertilization rate. Also, the split urea fertilizer application appeared as the more effective strategy for N fertilization of overwinter spinach in comparison with the use of the nitrification inhibitor containing urea fertilizer, being the last strategy not able to adequately match the N crop demand.     

White lupine as a beneficial crop in Southern Europe. II. Nitrogen recovery in a legume–oat rotation and a continuous oat–oat

One experiment lasting for two years was carried out at Pegões (central Portugal) to estimate the impact of mature white lupine residue (Lupinus albus L.) on yield of fodder oat (Avena sativa L. cv. Sta. Eulalia) as the next crop in rotation, comparing with the continuous cultivation of cereal, under two tillage practices (conventional tillage and no-till) and fertilized with five mineral nitrogen (N) rates, with three replicates. Oat as a first crop in the rotation provided more N to the agro-ecosystem (63 kg N ha⁻¹) than did lupine (30–59 kg N ha⁻¹). This was at a cost of 100 kg of mineral N ha⁻¹, whereas lupine was grown without addition of N. A positive response of oat as a second crop was obtained per kg of lupine-N added to the system when compared with the continuous oat–oat. The cereal also responded positively to mineral N in the legume amended soil in contrast with the oat–oat sequence where no response was observed, partly due to the fast mineralization rate of lupine residue and a greater soil N immobilization in the continuous oat system. Each kg N ha⁻¹ added to the soil through the application of 73 kg DM ha⁻¹ mature lupine residue (above- and belowground material) increased by 72 kg DM ha⁻¹ the oat biomass produced as the second crop in rotation when 150 kg mineral N ha⁻¹ were split in the season, independent of tillage practice. Mature legume residue conserved in the no-tilled soil depressed the yield of succeeding cereal but less than the continuous oat–oat for both tillage practices, where the application of mineral N did not improve the crop response.     

Improved persistence of red clover (Trifolium pratense L.) increases the protein supplied by red clover/grass swards grown over four harvest years

UK livestock agriculture can significantly reduce its protein imports by increasing the amount of forage based protein grown on-farm. Forage legumes such as red clover (Trifolium pratense L.) produce high dry matter yields of quality forage but currently available varieties lack persistence, particularly under grazing. To assess the impact of red clover persistence on protein yield, diploid red clover populations selected for improved persistence were compared with a range of commercially available varieties. All populations were grown over four harvest years in mixed swards with either perennial ryegrass (Lolium perenne L.) or perennial plus hybrid ryegrass (L. boucheanum Kunth). Red clover and total sward dry matter (DM) herbage yields were measured in Years 1–4, red clover plant survival in Years 3 and 4 and herbage protein (CP) yield and concentration in Years 2 and 4. In general, red clover DM yield in year 4 (3.4 t ha⁻¹) was lower than in year 1 (13.9 t ha⁻¹) but the red clover populations differed in the extent of this decline. Differences in the persistence of the red clover populations in terms of plant survival and yield were reflected in the contribution of red clover to the total sward yield in Year 4, which ranged from 61% for the highest yielding population, AberClaret, to 11% in the lowest yielding, Vivi. Increased red clover DM yield was reflected in a greater CP yield (protein weight per unit area), which ranged from 1.6 t ha⁻¹ year⁻¹ to 2.9 t ha⁻¹ year⁻¹ in Year 2 and from 1.1 t ha⁻¹ year⁻¹ to 1.9 t ha⁻¹ year⁻¹ in Year 4. CP concentration (protein weight per unit herbage weight) of all of the red clover populations was within a range considered suitable for ruminant production. The implication of these results for the future use of red clover in sustainable grassland systems is discussed.     

Biomass production and N balance of giant reed (Arundo donax L.) under high water and N input in Mediterranean environments

This study aimed to evaluate the productivity of Arundo donax under good water and N availability coming from non-conventional sources, in different Italian environments (Padova and Bologna in the north, Reggio Calabria and Catania in the south) in relation to three harvest periods (autumn; mid-winter; late-winter).In the northern locations A. donax had already reached maximum productivity the year after transplanting, with 85 and 98 t ha⁻¹ of dry matter at Padova and Bologna, respectively. At Reggio Calabria and Catania a further biomass increase was obtained from the second to third year of cultivation, when production was 62 t ha⁻¹ and 51 t ha⁻¹, respectively.The average dry matter production was 74, 66 and 65 t ha⁻¹ with autumn, mid-winter and late-winter harvesting, respectively.Under N input ranging from 225 to 329 kg ha⁻¹ year⁻¹ at the different locations, the apparent N balance (input–output) was negative except in Catania indicating a great potential of A. donax to provide high N uptake, which would be a useful feature in environments under the European Nitrates Directive.     

Maize yield and water balance is affected by nitrogen application in a film-mulching ridge–furrow system in a semiarid region of China

Poor soil and drought stress are common in semiarid areas of China, but maize has a high demand for nitrogen (N) and water. Maize production using the technique of double ridges and furrows mulched with plastic film are being rapidly adopted due to significant increases in yield and water use efficiency (WUE) in these areas. This paper studied N use and water balance of maize crops under double ridges and furrows mulched with plastic-film systems in a semiarid environment over four growing seasons from 2007 to 2010. To improve precipitation storage in the non-growing season, the whole-year plastic-film mulching technique was used. There were six treatments which had 0, 70, 140, 280, 420 or 560 kg N ha⁻¹ applied in every year for maize. In April 2011, spring wheat was planted in flat plots without fertilizer or mulch following four years of maize cultivation. After four years, all treatments not only maintained soil water balance in the 0–200 cm soil layer but soil water content also increased in the 0–160 cm soil layer compared to values before maize sowing in April 2007. However, under similar precipitation and only one season of spring wheat, soil water content in the 0–160 cm soil layer sharply decreased in all treatments compared to values before sowing in April 2011. Over the four years of maize cultivation, average yield in all treatments ranged from 4071 to 6676 kg ha⁻¹ and WUE ranged from 18.2 to 28.2 kg ha⁻¹ mm⁻¹. In 2011, the yield of spring wheat in all treatments ranged from 763 to 1260 kg ha⁻¹ and WUE from 3.5 to 6.5 kg ha⁻¹ mm⁻¹. The potential maximum grain yield for maize was 6784 kg ha⁻¹ with 360 kg N ha⁻¹ applied for four years, but considerable NO₃N accumulated in the soil profile. A lesser application (110 kg N ha⁻¹) to this tillage system yielded in 82% of the maximum, increased nitrogen use efficiency and mitigated the risk of nitrogen loss from the system. This study suggests that double ridge–furrow and whole-year plastic-film mulching could sustain high grain yields in maize with approximately 110 kg N ha⁻¹ and maintain soil water balance when annual precipitation is >273 mm in this semiarid environment.     

Pig slurry fertilization in a double-annual cropping forage system under sub-humid Mediterranean conditions

In areas of Southern Europe with very intensive pig production, most of the pig slurry (PS) is applied as fertilizer. However, in the European Union, no more than 170 kg N ha⁻¹ year⁻¹ can be applied in nitrate vulnerable zones (NVZs) from livestock manures. In this context, a six-year trial was conducted for a maize-triticale double-annual forage cropping rotation under rainfed conditions. Four different N rates were applied (0, 170, 250 and 330 kg N ha⁻¹ year⁻¹), to evaluate their effect on crop yield, N uptake, unrecovered N and soil nitrate content. The corresponding PS rates were defined as zero (PS 0), low (PSL) medium (PSM) and high (PSH). The annual average dry matter (DM) yields (maize + triticale) for the PS fertilization treatments PS0, PSL, PSM and PSH were 12.6, 17.7, 20.2 and 22.0 Mg DM ha⁻¹, respectively. Maize DM yield was influenced mainly by weather conditions, and triticale DM yield was clearly influenced by initial soil NO₃⁻-N and PS fertilization rates. Unrecovered N was affected by PS fertilization rate and initial soil NO₃⁻-N content. A residual effect of the PS when applied to maize had an important effect on soil NO₃⁻-N and subsequent triticale DM yield. Moreover, total annual average unrecovered N, considering the sum of both crops (maize + triticale), were 91, 144, and 222 kg N ha⁻¹ in PSL, PSM and PSH, respectively. In order to avoid part of this unrecovered N, mainly by lixiviation of nitrates, PS fertilization in triticale should be applied as side dressing at tillering. The application of N, in the form of PS, at rates higher than the legally permitted maximum of 170 kg N ha⁻¹ year⁻¹, may result in better yields. However, high rates of PS fertilization may originate in significantly lower N use efficiency and a higher potential environmental impact in double-cropping systems, practiced in rainfed sub-humid Mediterranean conditions.     

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.     

Cassava yield loss in farmer fields was mainly caused by low soil fertility and suboptimal management practices in two provinces of the Democratic Republic of Congo

A better understanding of the factors that contribute to low cassava yields in farmers’ fields is required to guide the formulation of cassava intensification programs. Using a boundary line approach, we analysed the contribution of soil fertility, pest and disease infestation and farmers’ cultivation practices to the cassava yield gap in Kongo Central (KC) and Tshopo (TSH) provinces of the Democratic Republic of Congo. Data were obtained by monitoring 42 and 37 farmer-managed cassava fields during two cropping cycles in KC and one cropping cycle in TSH, respectively. Each field was visited three times over the cassava growing period for the observations. Logistic model was fitted against the observed maximum cassava root yields and used to calculate the achievable yield per field and for individual factor. At field level, the factor that led to the lowest achievable yield (Y_up(i)1) was considered as the dominant yield constraint. Cassava yield loss per field was expressed as the increase in the maximal root yield observed per province (Y_att- attainable yield) compared to Y_up(i)1. Y_att was 21 and 24 t ha⁻¹ in TSH and KC, respectively. With the cassava varieties that farmers are growing in the study areas, pests and diseases played a sparse role in the yield losses. Cassava mosaic was the only visible disease we observed and it was the dominant yield constraint in 3% and 12% of the fields in KC and TSH, respectively. The frequent yield constraints were suboptimal field management and low soil fertility. Cultivation practices and soil parameters led to Y_up(i)1 in 47% and 50% of the fields in KC, and in 47% and 41% of those in TSH, respectively. Individual soil parameters were the yield constraint in few fields, suggesting that large-scale programs in terms of lime application or recommendation of the blanket fertilisers would result in sparse efficacy. In KC, yield losses caused by low soil fertility averaged 6.2 t ha⁻¹ and were higher than those caused by suboptimal field management (5.5 t ha⁻¹); almost nil for cassava mosaic disease (CMD). In TSH, yield losses caused by low soil fertility (4.5 t ha⁻¹) were lower than those caused by suboptimal field management (6.5 t ha⁻¹) and CMD (6.1 t ha⁻¹). Irrespective of the constraint type, yield loss per field was up to 48% and 64% of the Y_att in KC and TSH, respectively. Scenario analysis indicated that the yield losses would remain at about two third of these levels while the dominant constraint was only overcome. We concluded that integrated and site-specific management practices are needed to close the cassava yield gap and maximize the efficacy of cassava intensification programs.     

Evaluation of cover-cropping managements on productivity and N-utilization efficiency of kenaf (Hibiscus cannabinus L.), under different nitrogen fertilization rates and soil types

Biomass productivity, nitrogen recovery fraction and nitrogen utilization efficiency (NUE) of kenaf (Hibiscus cannabinus L.) cultivar Tainung 2 were tested, under three Lens culinaries treatments (incorporated, harvested before the sowing of the energy crop and mono-cropping) and four nitrogen dressings (0, 50, 100 and 150 kg ha⁻¹), in two field experiments carried out on a fertile, clayey to loamy soil, and on a sandy soil of moderate fertility, in central Greece, over the period 2007–2009. The obtained results showed a positive response in L. culinaries cover cropping on kenaf total yield, on both experimental sites. Total dry biomass fluctuated from 16.07 to 21.46 t ha⁻¹ for incorporated plots and from 13.63 to 16.55 t ha⁻¹ for control treatments (relied only on applications of N-fertilization) for sandy soil, and from 14.98 to 19.28 t ha⁻¹ in case of legume incorporation and from 12.34 to 16.69 t ha⁻¹ for control plots, for clayey soil, respectively. The evaluated NUE was 76 kg kg⁻¹, for sandy soil, and 72 kg kg⁻¹, for clay soil. The recovery fraction escalated from 41% in control plots to 70% in plots with previous L. culinaries cultivation for sandy soil, while for clayey soil an increase of 20% was recorded, indicating a prominent effect of legume cover-cropping management.     

Forage production,quality and water-use-efficiency of four warm-season annual crops at three sowing times in the Loess Plateau region of China

Increasing demand for livestock products is driving development of livestock systems worldwide. That requires improved and new forage production options. The Loess Plateau region in central-northern China is an important area for livestock production, as it supports11% and 19% of the country’s cattle and sheep, respectively (China statistical yearbook 2014). The rain-fed semi-arid environment of the Loess Plateau means that maximizing the water-use-efficiency (WUE) of forage production is vital to guarantee enough fodder supply the livestock demand. A three-year field experiment in north-west Loess Plateau compared forage production, water use and water-use-efficiency as well as crude protein (CP) content of forage maize, Sudan grass, foxtail millet and Japanese millet sown at three sowing dates according to the opening rain during 2011–2013. On average, forage maize produced the highest biomass (12.1 t ha⁻¹) and had the highest WUE (43.4 kg DM ha⁻¹ mm⁻¹). This was followed by Sudan grass (7.8 t ha⁻¹; 26.5 kg DM ha⁻¹ mm⁻¹), Japanese millet (6.7 t ha⁻¹; 26.2 kg DM ha⁻¹ mm⁻¹) and foxtail millet (6.7 t ha⁻¹; 24.6 kg DM ha⁻¹ mm⁻¹). Optimizing sowing date played an important role in maximizing forage production and WUE of all tested forages. Compared to the earliest sowing date, a delay of two weeks reduced forage production by 17% in maize, 35% in foxtail millet, and 16% in Japanese millet. A delay of four to six weeks reduced biomass yield by 58% in maize, 57% in foxtail millet, and 56% in Japanese millet. Late sowing also greatly reduced WUE of forage maize and foxtail millet by 33% and 42%, respectively, when compared to early sowing. The middle sowing date maximized forage production and WUE of Sudan grass in two of the three growing seasons, which was 20% and 38% higher than the early and late sowing, respectively. Late sowing in all forages reduced crop water use by 42–57 mm compared to the early sowing. Among four test crops, CP of Sudan grass (7.9%) and forage maize (7.7%) was higher than foxtail millet (6.8%) and Japanese millet (6.7%). Compared with early sowing, CP_f in late sowing significantly increased in Sudan grass and decreased in Japanese millet, in contrast, no evident sowing date effect was found in forage maize and foxtail millet. This study showed that all four warm-season annual grasses had high forage production potential, forage maize was the most reliable and efficient option. Forage maize and the millets could easily be integrated into existing cropping systems and provide opportunities as both grain and forage-producing crop to provide added flexibility for farmers.     

Evaluation of nitrogen management in maize cultivation grows on soil amended with sewage sludge and urea

This paper analyses the data of a 3 years’ research on the agronomical use of sewage sludge, from a urban waste water plan, to grow maize (Zea mays L.). The experiment was conducted in order to test possible combinations of sewage sludge and urea as source of nitrogen for maize. The experiment comprised a randomized block design composed of a control and 8 treatments with four replicates. Three urea rates (0; 100 kg N ha⁻¹ and 200 kg N ha⁻¹) were assigned combined with three sewage sludge rates (0; 5 t ha⁻¹ and 10 t ha⁻¹), exceeding the limits permitted by the law, and the unfertilized control. Maize was sown and harvested for 2 years (April–September 2006 and 2007) and wheat (Triticum vulgare L.) was sown in October 2007 and harvested in May 2008 without adding any fertilizer or sewage sludge, in order to evaluate the residual effects of the organic fertilizer.The batch that gave the highest grain production was the one that received 10 t ha⁻¹ DM of sewage sludge and 100 kg N ha⁻¹ from urea, reaching values of 16.17 ± 0.97 t ha⁻¹ DM in the first year and 17.52 ± 0.68 t ha⁻¹ DM in the second one, while the effect of the organic fertilization was still available where wheat was grown. ANR values showed a significant increase between the first and the second year: the average value for the treatment 3 (exclusive use of sludge in maximum dose) has shown an increase from 24.3% in 2006 to 63.4% in 2007, highlighting the effect of the sewage sludge. Yields and nitrogen uptake during and after the experiment and the nitrate losses by leachates have been evaluated: linear correlations were statistically significant, with an improvement in the second year of the trial, between yields and the nitrogen applied (R² = 0.757) and yields and the nitrogen removal rate (R² = 0.843).     

Yield,water use and radiation use efficiencies of kenaf (Hibiscus cannabinus L.) under reduced water and nitrogen soil availability in a semi-arid Mediterranean area

Kenaf is a warm-season species that recently has been proved to be a good source of biomass for cellulose pulp for the paper industry in Mediterranean countries, where the use of hemp is problematic for legal reasons. A two-year research program aiming at studying the effects of different water regimes and nitrogen fertilization levels, upon plant growth, leaf area index, biomass accumulation, water and radiation use efficiency, was carried out on kenaf under a typically semi-arid Mediterranean climate of South Italy. In cv. Tainung 2, four different water regimes (I₀ = no irrigation, I₂₅, I₅₀ and I₁₀₀ = 25, 50 and 100% ETc restoration, respectively) and three nitrogen levels (N₀ = no nitrogen, N₇₅ and N₁₅₀ = 75 and 150 kg ha⁻¹ of N, respectively) were studied. The amount of water applied strongly affected plant growth (in terms of LAI, plant height and biomass) and final total and stem dry yield, which significantly increased from I₀ to I₁₀₀. Nitrogen did not exert any beneficial effect upon dry yield. Radiation Use Efficiency (RUE), calculated in the second year only, was the highest (1.95 g DM MJ⁻¹) in fully irrigated treatment (I₁₀₀) and the lowest (0.86 g DM MJ⁻¹) in the dry control.Water use efficiency (WUE) was rather similar among water regimes, whilst irrigation water use efficiency (IWUE) progressively increased with the decrease of total volume of water distributed to the crop by irrigation, from 3.47 to 12.45 kg m⁻³ in 2004 and from 4.27 to 7.72 kg m⁻³ in 2005. The results obtained from this research demonstrate that in semi-arid areas of South Italy, irrigation at a reduced rate (50% ETc restoration) may be advantageous, since it allowed a 42–45% irrigation water saving, when compared to the fully irrigation treatment, against a 23% (in 2004) and 36% (in 2005) yield reduction, and a still good efficiency (near that potential) in transforming the solar radiation in dry biomass was maintained (RUE = 1.76 g DM MJ⁻¹, against 1.95 g DM MJ⁻¹ in fully irrigated treatment).     

Phosphorus management in low input stockless cropping systems: Crop and soil responses to contrasting P regimes in a 36-year experiment in southern France

Fertiliser recommendation systems should aim at a finer tuning of non-renewable P inputs for agronomic, environmental and economic reasons. Modern decision support systems should take into account the relevant soil characteristics, the P recycling capabilities of the cropping system, and crop requirements for attainable production in a range of soil/weather conditions. Unfortunately, information is still lacking for low input cropping systems in south-western France. In 1968 INRA Toulouse set up a P experiment, which has been going on for 36 years, on a deep alluvial silty-clay/clay soil with varying CaCO₃. Four P regimes (P0, P1, P2, P4) were arranged in four blocks with periodic changes in the fertiliser dressings. Wheat, maize, sunflower, sorghum and soybean were tested for grain yield (GY) and grain P concentration (GPC) response to soil Olsen P concentration. The highest GY were observed in both P2 and P4, although P1 yields were significantly lower in only 4 years out of 36. P0 resulted 32 times in lower yields than P2–P4 and 27 times in lower yields than P1. Wheat was the crop most sensitive to the absence of P fertilization (GY_P0/GY_Pmax = 0.72); maize and sorghum were intermediate (0.77) and sunflower was the less sensitive on average (0.83). As the highest GPC values were observed in the P4 treatments, P removal was maximum for P4 (21.9 kg P ha⁻¹ year⁻¹) and minimal in P0 (11.7 kg P ha⁻¹ year⁻¹). The critical soil Olsen P values for yield responses were determined using the Cate–Nelson and Mitscherlich approaches. Although the thresholds differ for the two methods (3.3–7.2 mg P kg⁻¹ with Cate–Nelson; 4.4–11.2 mg P kg⁻¹ with Mitscherlich), crops ranked similarly with both methods. Critical soil P values were lowest for maize and highest for sunflower, while wheat, soybean and sorghum had intermediate values. Because of low-input management and frequent water stress, critical values fall within the lower range of published values. Only in the P4 treatment were P-Olsen values potentially hazardous for the environment (>20 mg P kg⁻¹) 8–10 years after the beginning of the experiment. Annual P dressings of 17.5 kg P ha⁻¹ year⁻¹ (P1) were sufficient to achieve good yields but P dressings of 35 kg P ha⁻¹ year⁻¹ (P2) were necessary to stabilize soil P around the critical level in the calcareous part of the experiment.     

Optimized single irrigation can achieve high corn yield and water use efficiency in the Corn Belt of Northeast China

Decreasing the corn (Zea mays L.) gap between the potential yield and farm yield and reducing the risk of grain yield of drought are very important for corn production in the Corn Belt of Northeast China (CBNC). To achieve a high and stable corn yield, the effects of supplementary irrigation on yield, water use efficiency (WUE) and irrigation water use efficiency (IWUE) were studied using a modelling approach. The Root Zone Water Quality Model 2 was parameterized and evaluated using two years of experimental data in aeolian sandy soil and black soil. The evaluated model was then used to investigate responses to various irrigation strategies (rainfed, full irrigation and 12 single irrigation scenarios) using long-term weather data from 1980 to 2012. Full irrigation guarantees a high and stable corn grain yield (12.92 Mg ha⁻¹ and has a coefficient of variation (CV) of 14.8% in aeolian sandy soil; 12.30 kg Ma⁻¹ and CV of 11.1% in black soil), but has a low water use efficiency (19.92 and 21.81 kg ha⁻¹ mm⁻¹) and a low irrigation water use efficiency (10.01 and 11.03 kg ha⁻¹ mm⁻¹). A single irrigation can increase corn yields by 3–35% for aeolian sandy soil and 5–35% for black soil over different irrigation dates compared with no irrigation. The most suitable single irrigation date was during late June to early July for aeolian sandy soil (yield = 10.73 Mg ha⁻¹ and WUE = 27.94 kg ha⁻¹ mm⁻¹) and early to mid-July for black soil (yield = 11.20 Mg ha⁻¹ and WUE = 27.70 kg ha⁻¹ mm⁻¹). The lowest yield risk of falling short of the yield goal of 8, 9, and 10 Mg ha⁻¹ were 9.1%, 18.2%, and 33.33% in aeolian sandy soil and 3.0%, 15.25, and 21.2% in black soil when an optimized single irrigation was applied in late June or early July, respectively. Therefore, an optimized single irrigation should be applied in late June to early July with the irrigation amount to refill soil water storage of root zone to field capacity in CBNC.