Increase In Total Dry Matter Research Articles

Forage quality in cereal/legume intercropping: A meta-analysis

ContextMeta-analyses have highlighted several advantages of cereal/legume intercropping for food compared to sole cropping, but none report on fodder quality and yield. In forage production, mixtures may more effectively balance fiber and crude protein concentrations of the forage in view of nutrient requirements of ruminants than sole crops. However, productivity, quality and the trade-off between these in cereal/legume intercropping of fodder species have not been systematically reviewed. ObjectiveThis paper reports on a meta-analysis of a database of global literature on intercropping of forage-producing cereal and legume crops to evaluate the effect of intercropping on dry matter (DM), crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), non-CP non-NDF yields and concentrations of intercrops as compared with the respective sole crops. MethodsA literature search was carried in Web of Science searching in ‘all fields’ with as search terms: (intercrop* OR “mixed crop*” OR “crop mix* ” OR “mixed cultivation*” OR “polyculture*” OR “row crop*”) AND (forage OR fodder) AND (quality OR "nutri* content" OR "nutri* concentration" OR "nutri* value"). Out of the 759 papers further selection yielded a database based on 61 publications on cereal/legume intercropping reporting total biomass and at least one quality component for both sole crops and their intercrops. ResultsThe net effects for DM (1.76 ± 0.38 Mg/ha), CP (0.20 ± 0.05 Mg/ha), NDF (1.01 ± 0.25 Mg/ha), ADF (0.63 ± 0.15 Mg/ha) and non-CP non-NDF (0.76 ± 0.22 Mg/ha) yields showed production of all increased upon intercropping. The difference in relative increase in total DM and the four components did not lead to any change in %CP, %NDF, %ADF and %non-CP non-NDF. The change in DM yield was due to enhanced cereal yield. Moreover, the cereal %CP in the intercrops was higher than expected and the cereal %NDF and %ADF in the intercrops was lower than expected, while the overall quality of the legume in the intercrops did not change. ConclusionIntercropping cereal and legume species will neither improve nor reduce the quality of produced feed, but it makes more effective use of the land through a higher production per unit area. SignificanceThis study reports the combined forage quality and quantity in cereal/legume intercropping. The quantity/quality balance of forage production with cereal/legume intercrops is necessary to design intercropping for forage production. The results can be utilized to establish cereal/legume intercropping systems with different forage production aims.

Straw Mulching under a Drip Irrigation System Improves Maize Grain Yield and Water Use Efficiency

ABSTRACTReasonable use of water is required for the sustainable development of maize production in the North China Plain (NCP). In this study, straw mulching (SM) was evaluated in a 2‐yr field experiment to determine whether its effect on maize (Zea mays L.) yield and water use efficiency (WUE) differed under different irrigation systems. Compared with no mulching (NM) treatment, SM increased maize yield by 10.6 and 12.5% under a drip irrigation system in 2016 and 2017, respectively, which was mainly attributed to an 11.7 and 13.5% increase in total dry matter (DM). The increased soil water content in the 0‐ to 40‐cm layer at the six‐leaf (V6), silking (R1), and maturity (R6) stages for SM improved the soil mineral N content (Nmin) in that layer and then increased the N accumulation from V6 to R1 and post‐silking by 7.6 and 21.1% averaged over 2 yr compared with NM, respectively. The enhanced N accumulation for SM increased the leaf area index and DM accumulation rate, which increased the DM accumulation from V12 to R1 and post‐silking by 16.2 and 16.4% averaged over 2 yr compared with NM, respectively, and then the grain number and grain weight. Straw mulching also improved the WUE under the drip irrigation system due to the greater grain yield and 6.1% lower water consumption. This demonstrated that SM combined with the drip irrigation system effectively improved the yield and WUE of maize due to improved DM and N accumulation promoted by the increased water content and Nmin in the upper soil layers.

Bacterial Formulations in Induction of Resistance and Growth Promotion of Tomato Plants

The objective of this work was to evaluate the effectiveness of seed treatment with fresh suspensions and powder formulations with Bacillus methylotrophicus to promote plant growth and induction of resistance against fusarium wilt (Fusarium oxysporum f. sp. lycopersici) in tomato plants under greenhouse conditions, verifying the occurrence of morphological and biochemical changes in the evaluated plants. Powder formulations based on Cassava (Manihot esculenta), Arrowroot (Maranta arundinacea) and sodium alginate containing Bacillus, in addition to the commercial product Quartz®, were used to microbiolize the tomato seeds of the cultivar Santa Cruz. The formulations promoted plant growth, with a seedling vigor index greater than 50% for all treatments containing B. mthylotrophicus, in addition to a significant increase in total dry matter. The treatments induced systemic resistance, controlling the fusarium wilt with a 75% reduction of the disease and activation of enzymes such as peroxidase and polyphenoloxidase, only β-1,3-glucanase presented less activity than controls (treatments without B. mthylotrophicus). Thus, the use of formulations containing Bacillus are efficient in promoting plant growth of tomato plants and in inducing resistance to the control of fusarium wilt.

Effectiveness of halo-tolerant, auxin producing Pseudomonas and Rhizobium strains to improve osmotic stress tolerance in mung bean (Vigna radiata L.)

Halo-tolerant, auxin producing bacteria could be used to induce salt tolerance in plants. A number of Rhizobium and auxin producing rhizobacterial strains were assessed for their ability to tolerate salt stress by conducting osmoadaptation assay. The selected strains were further screened for their ability to induce osmotic stress tolerance in mung bean seedlings under salt-stressed axenic conditions in growth pouch/jar trials. Three most effective strains of Rhizobium and Pseudomonas containing ACC-deaminase were evaluated in combination, for their ability to induce osmotic stress tolerance in mung bean at original, 4, and 6 dS m(-1) under axenic conditions. Results showed that sole inoculation of Rhizobium and Pseudomonas strains improved the total dry matter up to 1.4, and 1.9 fold, respectively, while the increase in salt tolerance index was improved up to 1.3 and 2.0 fold by the Rhizobium and Pseudomonas strains, respectively. However, up to 2.2 fold increase in total dry matter and salt tolerance index was observed due to combined inoculation of Rhizobium and Pseudomonas strains. So, combined application of Rhizobium and Pseudomonas strains could be explored as an effective strategy to induce osmotic stress tolerance in mung bean.

Crescimento e Rendimento Produtivo do Feijoeiro Submetido à Restrição Hídrica

The bean crop is affected by climate conditions, where plant development is influenced by water stress. One of the ways to meet the needs of the plant is through irrigation. Thus, in this work we sought to investigate the vegetative growth and production yield of the bean subjected to water stress during its cycle. For this purpose, beans of the cultivar Manteiga were cultivated in 5 dm3 pots and subjected to treatments of 50 and 100% field capacity. The parameters analyzed were: plant height, leaf area, number of root nodules, dry weight of the shoots, roots and total, dry mass of the grains and grain number and grain yield. According to the data obtained the following growth indexes were determined: increase of total dry matter and that of the stem, leaf and root. The experiment was conducted in a greenhouse at the Federal University of Vicosa, arranged in a randomized complete block design in a split-plot in time, with four replications. The results showed that there was lower vegetative growth and lower production yield in plants subjected to water restriction, imposed by the treatment of 50% field capacity, indicating the need for adequate control of soil water management as a suitable strategy for production.

East African highland bananas (Musa spp. AAA-EA) ‘worry’ more about potassium deficiency than drought stress

Drought stress, potassium (K) and nitrogen (N) deficiencies are major constraints to rain-fed East African highland banana (EAHB) production in Uganda. It was hypothesised that the reduction in fresh bunch mass and increase in dry matter (DM) allocation to corms with drought stress, K and N deficiency is additive. Individual plant measurements at harvest from two field trials in central and south western Uganda were analyzed to evaluate effects of cumulative rainfall (CRF) received 365 days from sucker emergence, mineral K and N inputs on EAHB bunch yields. Dry matter content in aerial shoot (leaves and pseudostems) relative to that in the subterranean corm was also analyzed to evaluate DM allocation plasticity due to drought stress, K and N deficiency. This was verified with allometric analysis using pre-harvest stage plants from farms of known K and N nutritional status and plants from a screen house drought stress pot trial in Uganda. Dry matter production and yields were mainly driven by K interacting with CRF. Within 12 months, K input (250–600kgKha−1yr−1) increased bunch yield from 8 to 15Mgha−1yr−1 irrespective of whether dry (CRF<1100mm) or wet (CRF≥1100mm) conditions prevailed, possibly due to K-mediated osmotic adjustment under dry conditions. Without K input, wet conditions increased bunch yield from 6 to 8Mgha−1yr−1 while dry conditions decreased it from 6 to 4Mgha−1yr−1 within 12 months. Total DM and its distribution between the biomass structures followed similar trends. Nitrogen input (150–400kgNha−1yr−1) neither affected bunch yield nor DM allocation at harvest stage. At pre-harvest stage, reduction in DM allocation to the corm per unit increase in total DM was 14–22% significantly lower with N and/or K deficiency compared with that under sufficient K and N. Drought stress per se had no effect on DM allocation but enhanced DM allocation shifts due to K deficiency. Drought-stressed EAHB thus increase DM allocation to subterranean structures only if K-deficient, unlike responses reported for other plant species. Potassium nutrition is perhaps a more viable entry point for mitigation of drought stress in EAHB cropping systems than irrigation but this requires further agronomic and economic evaluation. It may be important to account for carbon allocated to osmotic adjustment for realistic simulation of water- and K-limited growth in EAHB.

Development of the nodulated soybean plant after flooding of the root system with different sources of nitrogen

Flooding leads to hypoxia, a stress to which symbiotic N2 fixation is especially sensitive. The response of fully nodulated soybean plants to a 21-day period of flooding was studied by measurements of growth parameters and xylem transport of organic nitrogenous components to the shoot, in the presence and absence of NO3- and NH4+ in the medium. Flooding was found to seriously impair N2 fixation, irrespective of the N source, as indicated by strongly reduced xylem ureide levels. In the absence of a source of N, growth was strongly reduced during flooding while accumulation of N in the shoot was virtually abolished. Flooding in the presence of 5 mM NO3- or NH4+ led to the accumulation of total N in the shoot but only NO3- promoted increases in total dry matter, plant height and leaf area above that found in the absence of N. The accumulation of N, however, was lower than that of the non-flooded control for both NO3- and NH4+. The increases in total dry matter, plant height and leaf area with NO3- was as high as those of the non-flooded control. These data clearly show the beneficial effects of NO3- during a prolonged period of flooding of the nodulated root system of soybean.

Effect of Nitrogen Fertilization on Photosynthetic Characters and Dry Matter Production in F1 Hybrids of Rice (Oryza sativa L.)

This study was carried out to determine heterosis in different photosynthetic and morphological characters, and to observe photosynthetic ability and dry matter production potentiality of two F1 hybrids of rice grown in pots supplied with N fertilizer in the normal or double dose. Photosynthetic rate in terms of CO2 exchange rate (CER), leaf N concentration, SPAD value, soluble protein content and ribulose-l,5-bisphosphate carboxylase (Rubisco) activity was increased significantly by doubling the dose of fertilizer in most parental cultivars and F1 hybrids, but the rate of increase was higher in F1 hybrids than in their parents. Several morphological parameters were also increased significantly by doubling the dose of fertilizer, but not the percentage of dead leaf blades. The rates of increase of plant height, leaf area and dry matter production were higher in F1 hybrids. In particular, the rates of increase of total dry matter and root weight were very high in one of the F1 hybrids. The percentage of dead leaf blades decreased significantly in plants grown with a high dose of fertilizer as a result of higher leaf N concentration. At a normal fertilizer dose, both F1 hybrids failed to show positive heterosis in most photosynthetic characters. However, positive heterosis was found at a high fertilizer dose. Both F1 hybrids showed positive heterosis over mid-parent in dry matter production per plant at both fertilizer doses. One of the F1 hybrids also showed positive heterosis over the better parent. Heterosis in most photosynthetic and morphological characters was increased by increasing the dose of fertilizer. The sufficient supply by doubling the dose of fertilizer increased the leaf N concentration, chlorophyll content, soluble protein content and Rubisco activity in F1 hybrids, which led to higher positive heterosis in CER. A larger leaf area plus higher CER, especially at a high fertilizer dose, contributed to higher dry matter production in F1 hybrids of rice.

Effects of Blue Light and Red Light on Kidney Bean Plants Grown under Combined Radiation from Narrow-Band Light Sources.

Kidney bean (Phaseolus vulgaris L.) plants were grown at different levels of blue and red light under broad-spectrum radiation over 12 d. Using four kinds of narrow-band fluorescent lamps, blue or red light was increased at the same levels of photosynthetic photon flux density (100μmol m-2 s-1) and red to far-red photon flux ratio (R: FR; 1.1) . Increases in both blue and red light caused increases in total dry matter, but also quite different dry matter distribution. Increasing blue light did not have a significant influence on leaf area but caused a large decrease in stem length. On the other hand, increasing red light caused both increases in leaf area and a small, but consistent, increase in stem length. The data suggest that increases in total dry matter are due to increases in dry matter production per unit leaf area in the case of increasing blue light, and on the other hand, due to increases in leaf area in the case of increasing red light. Besides the growth response caused by R : FR, the results indicate that increases in blue light cause great inhibition of stem extension and thickening of leaf, while increases in red light at constant R : FR accelerates both stem extension and leaf expansion without modifying leaf thickness.

Nutrients in the West African Sudano‐Sahelian zone: Losses, transfers and role of external inputs

AbstractCrop growth on acid sandy soils of the Sudano‐Sahelian zone is primarily limited by the low amounts of organic matter and available mineral nutrients in the topsoil. The shortening of fallow periods with population growth, the exploitation of fire wood, spatial nutrient transfers by wind and water and net nutrient exports with crop yields in the order of 15 kg nitrogen (N) 2 kg phosphorus (P) and 15 kg potassium (K) ha−1 yr−1 for traditional fields planted to pearl millet (Pennisetum glaucum L.) in the southern Sahel have exhausted these resources. Large productivity declines in the prevailing agro‐pastoral systems are the consequence. Data are presented to show bow nutrient exports at the level of individual fields, through grain yields and biomass removal as forage, firewood, construction material, and also through run‐off, wind and water erosion, leaching and volatilisation, are either losses for the ecosystem or sources of nutrients transferred within the ecosystem. Livestock is a vector of nutrients from rangelands to manured fields through forage intake and excretion and helps to shortcut nutrient cycles, but it is also a net consumer of organic matter and minerals. Through the effects of trampling on the soil and of grazing on the vegetation composition and production, livestock also indirectly affects the cycling and transfer of nutrients. Net nutrient inputs by heavy rains causing overland flow, dust deposition and through biological nitrogen fixation, are also unequally distributed and thus aggravate the fertility gradient from large nutrient ‘source’ areas such as rangelands to small ‘sink’ areas such as fallows, low lands, temporary lakes and river benches. At a finer resolution, shrubs and trees with their alternating periods of nutrient storage and recycling in leaves and wood, micro‐depressions, termite mounts and ant nests become localised points of nutrient concentration and high crop productivity. To balance losses of nutrients in these integrated systems and to obtain sustainable increases in production, external inputs of nutrients are necessary. These may be introduced by two different pathways, either via mineral fertilisers applied to croplands or via externally produced supplements fed to livestock. These pathways are complementary and each one has direct effects on the other. Fertiliser application to croplands affect livestock through the increase in available forage and crop residue feed, whereas feed supplementation affects crop production through higher amounts and better quality of manure. The adoption of either strategy by farmers requires a high nutrient use efficiency at low cost. Data from regional field trials revealed increases in total dry matter (TDM) of cereals with broadcast annual P application at 13 kg ha−1 ranging across three years from 19 to 88% for rockphosphate and from 34 to 102% for single superphosphate (SSP). Still, a low‐external input approach seemed more advantageous to farmers. The placement of NPK fertiliser at 4 kg P ha−1 with the seed at or shortly after planting caused average TDM increases of 70% for millet, sorghum, maize, cowpea and groundnut and showed an up to three‐fold higher phosphorus use efficiency than broadcast P. On the other hand, late dry season supplementation of grazing steers with millet bran not only decreased animal weight losses but also increased N and P concentrations in the faeces. The larger nutrient concentrations in the manure increased millet grain yield by 28% and stover yield by 21% on a field manured at a rate of 3 t DM ha−1. However, even with such approaches the current trends of declining soil productivity can only be reversed, if local policy makers are willing to support agricultural change through better terms of trade for agricultural products.

Effect of defoliation frequency on an irrigated perennial pasture in northern Victoria. 1. Seasonal production and sward composition

A field experiment was carried out to investigate whether changes in winter and post-winter defoliation frequency would increase the white clover content of an irrigated perennial ryegrass–white clover pasture in northern Victoria. Pastures defoliated every 4 weeks during winter had higher white clover growing point (stolon apices with at least 2 nodes) density at the end of winter than pastures defoliated every 8 weeks or those receiving a single defoliation after 16 weeks, but these differences did not affect the clover content in the spring. Reasons for this are suggested. Pastures defoliated at 8-week intervals in winter were the most productive over winter{early spring. Less frequent defoliation (4 v. 2 weeks) during the post-winter, September–May period reduced white clover growing point and perennial ryegrass tiller densities. However, the white clover growth rate during this period was increased by less frequent defoliation, whereas the ryegrass growth rate was reduced, resulting in an increase of 10% in the white clover content, and a 1·9 t dry matter (DM)/ha increase in total DM produced. This higher clover content and pasture yield during spring–autumn with less frequent defoliation has important implications for the management of irrigated perennial pastures for the dairy industry in northern Victoria.

Comparisons between an Upland and a Pima Cotton Cultivar: I. Growth and Yield

AbstractAmerican Pima cotton (Gossypium barbadense L.) is an extra‐long staple cotton produced in the southwestern USA and in other regions around the world. Pima cotton generally yields less than Upland (G. hirsutum L.), but there have not been any studies conducted to document the basis for these differences. Field trials were conducted at two south‐central Arizona locations from 1990 through 1992 for the purpose of comparing growth and yield between representative cultivars of Upland and Pima cotton. The aboveground portion of Upland ‘Deltapine 90’ (DPL 90) and Pima ‘S‐6’ were harvested and separated into stems, leaves (including petioles), burs (carpel walls), lint, and seeds. The bur fraction also included immature fruiting forms. Dry matter accumulation was modeled as a function of heat units (HU) accumulated after planting (HUAP). Both cultivars exhibited a linear increase of total dry matter over the duration of sampling. By the end of sampling, DPL 90 produced more total, stem, seed, lint, and reproductive (bur + seed + lint) dry matter than Pima S‐6; the dry matter that accumulated in leaves, bur fraction, and vegetative structures (leaf + stem) did not differ. The reproductive/vegetative ratio (RVR) was found to be similar for both cultivars, increasing rapidly with HU accumulation. Comparisons of lint dry matter accumulation as a function of RVR and harvest index (HI) revealed that DPL 90 yields more lint than Pima S‐6 due to a greater total biomass production and more efficient partitioning of dry matter into reproductive organs.

Photosynthetic potential of Thymus vulgaris selections under two light regimes and three soil water levels

A greenhouse experiment was conducted to measure the effects of two light regimes (LR) (supplemental, SL of 200 μmol m −2 s −1 and natural, NL) and three different soil water levels (SWL) (50, 70 and 90% field capacity) on biomass production, relative growth rate (RGR), net CO 2 assimilation ( Pn), stomatal ( g s ) and mesophyll ( g m ) conductance, chlorophyll a and b (chl a and chl b) content and leaf water potential (LWP) on two Thymus vulgaris L. clonal selections. There was a significant increase in total dry matter (DM) production and RGR due to SL and increased SWL. The highest Pn, 24.6 μmol CO 2 m −2 s −1, was obtained from Selection 1, grown under SL at 70% SWL. The lowest Pn, 6.3 μmol CO 2 m −2 s −1, was obtained from Selection 2, grown under NL at 50% SWL. Selection 1 had higher Pn, g s and g m than Selection 2 under all growing conditions. Thymus vulgaris leaves developed under SL were more quantum-use efficient than those grown under NL. Total leaf chlorophyll concentration per leaf area basis was significantly ( P ⩽ 0.01) higher in plants grown under SL than NL. The lowest LWP was recorded for Selection 2 grown under SL at 50% SWL.

Distribution of Cd and Zn in annual xylem rings of young spruce trees [Picea abies (L.) Karst.] grown in contaminated soil

Concentrations and total amounts of Cd and Zn in individual annual xylem increments of 5-year-old spruce trees (Picea abies) were investigated after one growing season in contaminated soils. The plants had been potted in soils amended with different concentrations of Cd and Zn and kept in open air conditions. In the outer xylem rings formed during the treatment period lowest concentrations of Cd and Zn were found. In inner rings concentrations of both elements increased and were highest at the pith. Total amounts of both elements showed reversed distribution patterns with highest values in the outermost rings. The observed increase of total dry matter of the rings from pith towards the outer rings was stronger than the parallel increase in total element amounts in the rings. Thus, concentrations dropped in younger rings. The time of the soil contamination event cannot be inferred from element concentrations in annual rings. The results challenge the concept of monitoring historical trends in trace element pollution using analytical data of tree rings of conifers.

Recurrent Selection for Maize Grain Yield: Dry Matter and Nitrogen Accumulation and Partitioning Changes

Recurrent full‐sib family and reciprocal recurrent selection have resulted in significant increases in grain weight of crosses between the varieties of maize (Zea mays L.) Jarvis Golden Prolific and Indian Chief. The objectives of this study were to (i) compare increases due to 14 cycles of recurrent full‐sib family selection, and reciprocal recurrent selection for yield in maize and (ii) determine whether increased grain weights were accompanied by parallel increases in total dry matter and total N accumulation. Unless total dry matter acquisition increases in parallel with grain weight during selection, sustained root and shoot functions would be restricted by excessive diversion of carbohydrates to grain. After 14 selection cycles on sandy soils of the North Carolina coastal plain, grain weight, dry matter accumulation, and N accumulation in the population hybrid increased 23, 12, and 4%, respectively, with full‐sib family selection and 27, 21, and I0%, respectively, with reciprocal recurrent selection. Greater proportions of the dry matter and N accumulated were partitioned to grain after full‐sib family selection than after reciprocal recurrent selection. Therefore, photosynthate production after full‐sib family selection was not sufficient to fully satisfy both the demand by grain and the requirements for root and shoot processes. Reciprocal recurrent selection resulted in a greater increase in photosynthate production, so that the hybrid population was able to meet the demand for carbohydrate by higher grain yield and still sustain N acquisition by roots. The conclusions were also supported by heterosis for grain weight, total dry matter, and total N accumulation, which was greater after reciprocal recurrent selection than after full‐sib family selection. Selection to increase grain weight will result in efficient N acquisition only when the greater grain weight is supported by an adequate increase in photosynthate production.

Yield production in two contrasting forms of spring-sown faba bean in relation to water supply

The production and grain yield of a semi-determinate (Minica) and a determinate variety (Ticol) of spring-sown faba bean were compared under five different irrigation treatments during 1986 and 1987 at the University of Nottingham. Although the number of reproductive structures (flowers and pods) was greater in Ticol than in Minica, grain yields were greater in Minica. The harvest index increased less rapidly in Ticol than in Minica for each increase in total dry matter. However, in both varieties grain yield was proportional to dry matter production which was greater in Minica. Since this proportionality was unaffected by irrigation treatment it was concluded that neither variety had a particular moisture-sensitive growth phase. Lower crop growth rates in Ticol than in Minica under non-irrigated conditions suggest that Ticol may be more susceptible to water stress than Minica.

Light Use, Water Uptake and Performance of Individual Components of a Sorghum/Groundnut Intercrop

SUMMARYThe productivity of each component of a sorghum/groundnut intercrop and its constituent sole crops is determined in terms of a ‘Crop Performance Ratio’ (CPR) defined as the productivity of an intercrop per unit area of ground compared with that expected from sole crops sown in the same proportions. The CPR allows productivity, intercepted radiation and seasonal transpiration to be compared so that conversion coefficients for radiation (e; g MJ−1) and dry matter/water ratios (q; g kg−1) can be calculated for each intercrop component and its constituent sole crops. In this experiment, CPR for total dry weight in the intercrop was 1.08 and that for reproductive yield was 1.27. These advantages in overall productivity and yield were typical of those reported elsewhere for sorghum/groundnut intercrops. The proportional increase in total dry matter in the intercrop was largely a result of its greater interception of radiation. The further advantage in reproductive yield was a consequence of an improved harvest index in the sorghum component of the intercrop (0.64) compared with that of its sole crop counterpart (0.55).

Light Use, Water Uptake and Performance of Individual Components of a Sorghum/Groundnut Intercrop

SUMMARYThe productivity of each component of a sorghum/groundnut intercrop and its constituent sole crops is determined in terms of a ‘Crop Performance Ratio’ (CPR) defined as the productivity of an intercrop per unit area of ground compared with that expected from sole crops sown in the same proportions. The CPR allows productivity, intercepted radiation and seasonal transpiration to be compared so that conversion coefficients for radiation (e; g MJ−1) and dry matter/water ratios (q; g kg−1) can be calculated for each intercrop component and its constituent sole crops. In this experiment, CPR for total dry weight in the intercrop was 1.08 and that for reproductive yield was 1.27. These advantages in overall productivity and yield were typical of those reported elsewhere for sorghum/groundnut intercrops. The proportional increase in total dry matter in the intercrop was largely a result of its greater interception of radiation. The further advantage in reproductive yield was a consequence of an improved harvest index in the sorghum component of the intercrop (0.64) compared with that of its sole crop counterpart (0.55).

Effect of rate and method of phosphate placement on productivity of durum wheat in mediterranean environments

Cereals grown on calcareous soils in a dry Mediterranean climate have generally responded to P fertilizer. Broadcasting is the common practice used by most farmers. The effects of rate and method of phosphate placement on dry matter production (TDM), grain yield and P uptake by durum wheat (Triticum vulgare L.) were investigated. Factorial experiments with four levels of P (0, 17.5, 35, and 52.5 kg P ha−1) and 2 methods of application (banding by drilling with the seeds, and broadcasting before surface tillage and sowing) were conducted for three consecutive seasons at three experimental sites: Breda (Typic Calciorthid, 281 mm); Tel Hadya (Chromoxeretic Rhodoxeralf, 328 mm) and Jindiress (Palexerollic Chromoxerert, 471 mm). Three levels of P were used in the third season only. Treatments were replicated in three blocks. The average values of NaHCO3-extractable P in the plow layer were 2.8, 3.7 and 2.1 mg P kg−1 at Breda, Tel Hadya, and Jindiress, respectively. Above-ground total dry matter (TDM) was determined at tillering and anthesis. Grain and straw yields were estimated separately at harvest. The P concentration in plant material was determined at both stages. At tillering, TDM and total P uptake (TPU) increased linearly with the rate of P applied. It was found that (i) 17.5 kg P ha−1 banded was as effective in increasing TDM and TPU as 52.5 kg P ha−1 broadcast, and (ii) the average relative percentage increase in TDM at tillering due to P banded as compared to P broadcast was 54%, with significantly less response to banding, by maturity and harvest. The response to P placement was found to be site related. At Breda, banding was found superior to broadcasting in all 3 seasons with a relative increase in grain yields equivalent to 34, 63 and 23% in the 3 successive seasons, when optimum amounts of P were applied. However, in two out of three seasons only banding was found superior to broadcasting at both Tel Hadya and Jindiress. As a result, banding P is recommended for durum wheat grown on the calcareous soils of the Mediterranean regions because it stimulates growth and P uptake early in the season and increases the crop potential for good grain and straw yields especially in dry areas. Given equal rates of P application, banding was found superior to broadcasting in most cases.

Recovery of15N from ammonium nitrate and algal biomass-amended soil

A greenhouse experiment was conducted to compare the effectiveness of blue-green algae (Anabaena flos aquae) produced in a simulated inorganic-wastewater medium and NH4NO3 as sources of N for bermudagrass (Cynodon dactylon L.) on a Decatur silt loam soil (clayey, kaolinitic, thermic Rhodic Paleudult).15N-labeled blue-green algae and15N-labeled NH4NO3 were used as N sources to supply up to 300 mg N per pot (3 kg of soil). Bermudagrass was clipped at 42, 63, and 102 d after planting and dry matter yield, total, and15N were determined at each clipping. Results indicated a highly significant increase in total dry matter (shoots and roots) and N uptake over the control for both algae and NH4NO3 treatments at all N rates. There were no significant effects of N source on bermudagrass yields, but total N uptake was significantly higher with NH4NO3. The net mineralization of N from blue-green algal biomass ranged from 36 to 59% of the total N applied and the corresponding net release for NH4NO3 ranged from 65 to 86%. From 29 to 54% of the total N applied as blue-green algal biomass and from 50 to 75% of the N applied as NH4NO3 were assimilated by bermudagrass plants. For N rates above 100 mg N pot−1, higher proportions of the labeled N in the shoots of the third harvest were derived from algal biomass than from NH4NO3. A large portion of the labeled N remained undecomposed or immobilized in the algae treated soil (41–64%) as compared to NH4NO3 treated soil (14–35%). More loss of N occurred in the NH4NO3 treatments from 3 to 15%, while the corresponding figures for algae treated soil were 2 to 8%.