Effect of soil compaction in the sub-humid cropping environment in Pakistan on uptake of NPK and grain yield in wheat (Triticum aestivum): I. Compaction

Soil compaction is a major cause of decrease in crop yield. The most serious cause of soil compaction is continuous ploughing at the same depth which affects bulk density, porosity and root proliferation, consequently affecting concentration and uptake of nutrients by plants. The effects of soil compaction on concentration and uptake of Nitrogen, Phosphorus and Potassium (NPK) by wheat were studied at the Agriculture Research Institute, Mingora, Pakistan in two separate experiments, conducted during 2002–2003 and repeated in 2003–2004. The treatments in each experiment consisted of four compaction levels arranged in a randomized complete block design replicated four times. Subsoil compaction affected soil bulk density and total porosity. With increasing compaction, bulk density increased in the range of 15–26% while total porosity decreased in the range of 15–27%. Compaction treatments significantly and progressively decreased concentration and uptake of NPK in both years of the experiments. Higher nutrient concentration and uptake was recorded during the second year as compared to first year, probably as a result of higher seasonal rainfall. Concentration of NPK showed reductions of 5–20%, 10–53% and 9–21%, respectively, due to the compaction treatments over control. The uptake of NPK decreased due to the compaction treatments in the range of 7–26%, 11–54% and 11–28%, respectively, over control. Compaction treatments decreased the dry matter accumulation in the range of 2–9% whereas grain yield showed a reduction of 5–48%. Inverse relationships between bulk density, and concentration and uptake of NPK, dry matter accumulation and grain yield were recorded. The implications of these findings for intensive agricultural systems in Pakistan and similar environments are discussed.     

Weed control with pre-emergence herbicides in vegetable soybean (Glycine max L. Merrill)

Field and laboratory experiments were conducted in the early and late rainy seasons in Thailand to evaluate the effect of pre-emergence application of herbicides and determine the herbicide residues on vegetable soybean (Glycine max L. Merrill cv. No. 75) production. No visible crop injury was observed after application of alachlor 469 g a.i./ha, clomazone 1080 g a.i./ha, metribuzin 525 g a.i./ha, pendimethalin 1031.25 g a.i./ha, tank-mixed clomazone 960 g a.i./ha + pendimethalin 928 g a.i./ha, or tank-mixed metribuzin 350 g a.i./ha + pendimethalin 928 g a.i./ha. However, acetochlor 1875 g a.i./ha, isoxaflutole 75 g a.i./ha, and oxadiazon 1000 g a.i./ha caused visible crop injury. Plant bioassay of herbicide residues in the soil after harvest showed no phytotoxic effect on baby corn (Zea mays Linn. cv. Suwan 3), cucumber (Cucumis sativus L. cv. Pijit 1), pak choi (Brassica chinensis Jusl. cv. Chinensis), and soybean (G. max L. Merrill cv. CM 60). Gas Chromatography-Mass Spectrometry (GC–MS) analysis showed no significant herbicide residues on crop yield (or MRLs < 0.01 ppm) for all herbicides used in this study. The application of metribuzin at 525 g a.i./ha was sufficient to provide satisfactory full-season control of several weed species and gave the highest crop yield. In addition, pendimethalin at 1031.25 g a.i./ha, and tank-mixed metribuzin at 350 g a.i./ha + pendimethalin at 928 g a.i./ha can provide a similar level of weed control as an alternative to reduce herbicide dosage thereby increasing food and environmental safety in vegetable soybean production.     

Is barley yield in the UK sink limited?: II. Factors affecting potential grain size

In the absence of serious post-anthesis stress, the potential supply of assimilates for grain filling in barley appears to exceed the storage (sink) capacity of the grains. The sink capacity is a function of the number of grains per unit land area and their potential size. In order to investigate the contribution of pre and early post-anthesis factors in the control of potential grain weight, regression analysis has been used to analyse data from field experiments conducted on winter barley crops cv. Pearl grown at six sites across the UK between 2002 and 2004. Crops were grown under a comparable husbandry regime with a full crop protection, growth regulator and fertilizer programme. The mean grain weight (MGW) varied from 35 to 46 mg at 100% dry matter over 17 site/year combinations. The variation in MGW between site/years was associated with differences in the rate rather than the duration of grain filling. MGW did not relate well to any measure of above ground growth or crop structure at ear emergence (Zadoks GS59). There was a significant positive linear relationship between MGW and the amount of radiation (PAR) intercepted per unit grain number between ear emergence and the start of rapid grain filling (r² = 0.32, P = 0.023), but not over the whole grain filling period. This is consistent with the view that MGW is determined by potential grain size. A multiple regression model comprising five explanatory variables accounted for a much larger proportion of the total variation in MGW (r² = 0.72, P = 0.013) than PAR interception on its own. There were significant positive associations of MGW with post-anthesis radiation use efficiency and PAR intercepted from GS59 to the start of rapid grain growth (RGG), and significant negative associations with the shoot number per plant, mean air temperature from GS39–59 and mean daily rainfall from GS59-RGG. The results suggest that both pre and post-anthesis conditions operate in concert to determine the potential grain weight of barley in temperate climates. The dry weight and water content of grains and ears followed a common pattern during grain growth for all site/years when the percentage moisture content was used as an index to normalise different rates of development. Use of the above data for predicting potential grain weight of barley prior to harvest is discussed.     

Genetic variability of transpiration response to vapor pressure deficit among soybean (Glycine max [L.] Merr.) genotypes selected from a recombinant inbred line population

Limited observations of soybean plant response of transpiration rate (TR) to vapor pressure deficit (VPD) have indicated the existence of genotypes with nearly constant TR at high VPD. The range of expression of this trait in a given population within a species has not been explored. To initiate study of this possibility, 22 genotypes from a RIL population derived from a cross of PI 416937 and Benning were characterized for their VPD response. Genotype PI 416937 has been shown to reach a maximum TR at a VPD as low as 2 kPa. Surprisingly, Benning was not found to have a continually increasing TR with VPD, but rather it had a two-segment TR response very similar to PI 416937. Unexpectedly, only one of the studied RILs had a TR response similar to the parents. Thirteen RILs had a continually increasing TR with increasing VPD. Eight RILs reached a maximum TR occurring at VPD of about 1.3 kPa, significantly lower value than that of the parents. While the inheritance of the maximum TR trait is clearly complex, these results offer encouragement that the VPD at which plants limit TR might vary so that the trait can be tailored to maximize potential yield increase in different water-deficit environments.     

Determinants of ruminant nutritional quality of pearl millet [Pennisetum glaucum (L.) R. Br.] stover: I. Effects of management alternatives on stover quality and productivity

The paper investigates management and cultivar type effects on pearl millet stover yield and fodder quality. Sixteen pearl millet cultivars available to farmers in India were selected to represent three cultivar types: (1) traditional landrace germplasm from the arid/semi-arid millet production zones, (2) improved dual-purpose (grain and stover) open-pollinated varieties incorporating differing amounts of traditional landrace germplasm and (3) commercial, grain-type F1 hybrids, bred for use in the arid/semi-arid zone. The cultivars were grown for 2 years (2000 and 2001) at high fertility (HF: 65 kg N ha⁻¹ and 18 kg P ha⁻¹) and low fertility (LF: 21 kg N ha⁻¹ and 9 kg P ha⁻¹). Within each fertility level high (HP) and low (LP) plant population densities were established by varying sowing rate and then thinning to the target populations (HP: 11 plants m⁻² and LP: 5 plants m⁻²). Stover fodder quality traits (nitrogen concentration, sugar content, in vitro digestibility and metabolizable energy content) were analyzed using a combination of conventional laboratory analysis and near infrared spectroscopy. In general, fertility level and cultivar type had strong effects on grain and stover yields, and on a range of stover nutritional quality traits, but with significant year interactions. In contrast, the effect of population density on these variables was largely insignificant. Higher fertilizer application significantly increased grain and stover yields and stover nitrogen concentration, in vitro digestibility and metabolizable energy content. As a result, fertilization resulted in significant increases in the yields of both digestible and metabolizable stover. Landrace cultivars as a group produced higher quality fodder than modern hybrids, but at a significant cost in grain yield. Dual-purpose, open-pollinated cultivars were generally intermediate between the landraces and hybrids, in terms of both stover quality and grain yield, but produced the highest yields of both digestible and metabolizable stover. The paper discusses the implications of these findings for Indian pearl millet farmers with various resource levels and farming objectives.     

Is barley yield in the UK sink limited?: I. Post-anthesis radiation interception,radiation-use efficiency and source–sink balance

Source or sink limitation of grain filling in cereals is often inferred from experiments in which the source:sink ratio is manipulated by shading, defoliation or grain removal. However, interpretation of this type of experiment is usually qualitative rather than quantitative in nature and the extent of any imbalance between the source and sink is not known. The objectives of the current work were: (1) to provide a detailed analysis of radiation interception, radiation-use efficiency (RUE) and carbohydrate storage reserves in winter barley in order to quantify the potential supply of photosynthates for grain filling; (2) to estimate the variation in source–sink balance between environments. Field experiments were conducted on cv Pearl at six sites in the UK and over 3 years. Crops were grown under a comparable husbandry regime at each site and received a full fertilizer and crop protection programme. When the cumulative interception of post-anthesis photosynthetically active radiation (PAR) was plotted against the increase in biomass to determine RUE, the pattern of response differed between sites and years; for some site/years the response was linear, for others it was non-linear where RUE decreased during the latter stages of grain filling. The extent and statistical significance of non-linearity was determined from the quadratic term of fitted 2nd order polynomials. There was no significant association between climatic variables, such as temperature, radiation or rainfall, and the value of the quadratic term of RUE. Neither could non-linearity of RUE be explained in terms of the shedding of leaf tissue during canopy senescence. There were weak associations (r² < 0.3) between the extent of non-linearity and green area index (GAI), above-ground biomass, and specific leaf N, at ear emergence (Zadoks GS 59). A much stronger relationship (r² = 0.63) was found between the source:sink ratio (green area per grain) at GS 59 and non-linearity of RUE. These results suggest that a major factor leading to the reduction in RUE during the second half of grain filling at some sites was feedback inhibition from a limited sink capacity. This conclusion is supported by a fairly strong positive association between RUE non-linearity and the apparent contribution of stem carbohydrate reserves to grain yield (r² = 0.47). The potential assimilate supply for grain filling was estimated as (maximum post-anthesis RUE × PAR intercepted) + stem soluble carbohydrate reserves at GS 59. The potential supply exceeded the measured yield at all sites except one implying that crops were predominantly sink limited. The size of the excess, which is a measure of the relative source–sink balance during grain filling, differed widely between site/years.     

Management and cultivar effects on ruminant nutritional quality of pearl millet (Pennisetum glaucum (L.) R. Br.) stover: II. Effects of cultivar choice on stover quality and productivity

The paper investigates the variation in laboratory fodder quality traits in stover of 16 cultivars of pearl millet grown over 2 consecutive years and subjected to two different fertilizer regimes and planting densities. Stover quality traits were nitrogen and sugar content, in vitro digestibility and metabolizable energy content as well as yield of digestible and metabolizable stover. Significant (P < 0.05) cultivar-dependent variations were observed for all these quality traits. Stover nitrogen contents were mostly below the levels (1.2% of dry matter) considered to be the minimum required for efficient feed digestion in the rumen, but choice of cultivar plus nitrogen fertilizer application could raise nitrogen levels to near, equal or above this threshold. Stover sugar contents were below 5% and mostly concentrated in the stems. Across management regimes stover in vitro digestibility varied by about 4% units, and by about 3–5% units within individual management regimes. Stover metabolizable energy contents of cultivars varied such that stover from superior cultivars could provide the energy maintenance requirement of livestock and theoretically moderate levels of live weight gains, while livestock fed on stover from poor cultivars would lose live weight. Yields of digestible and metabolizable stover (yield of stover dry matter times stover in vitro digestibility/metabolizable energy) varied among cultivars by at least 1.7-fold. Stover quality traits and grain yields of cultivars were largely unrelated (P > 0.05) suggesting that high stover quality will not be achieved on the expense of grain yield. Heritabilities for stover quality traits were high (h² > 0.73) except for stover nitrogen content (h² > 0.56).     

Arthropod communities related to different mixtures of oil (Glycine max L. Merr.) and essential oil (Artemisia annua L.) crops

Plants can host many herbivores and their natural enemies during their growth cycles. For this reason, changes in the relative abundance of crop and weed plants in a monocropping system as well as different crop plants in an intercropping system may produce great bottom up impacts in the specific and functional structure of spontaneous communities of arthropods. The hypothesis of this study was that the combination of two contrasting species, soybean (Glycine max, Fabaceae, N₂ fixing plant) and annual wormwood (Artemisia annua, Asteraceae, VOCs plant), would be related to different spontaneous communities of arthropods depending on the proportion of each species, and this would favor crop biodiversity without compromising crop production. The objectives of the study were: (a) to analyze the differences of spontaneous communities of arthropods related to different soybean (S)-annual wormwood (W) mixtures, using standard crop management for S production in Argentina, (b) to determine S and W total biomass and W essential oil content and yield and, (c) to analyze the relationship between arthropod communities and crop productivity. Factorial field experiments with 3 replications were done during 2006 and 2007. S density was kept constant (40 plants m⁻²) and different W densities (plants m⁻²) were added. Treatments were pure S, S + 2W, S + 4W, S + 8W and pure W (8 plants m⁻²). Arthropods were sampled at soybean full flowering and were classified in functional groups as herbivores and non-herbivores. S and W total and relative biomass and W essential oil content and yield from leaves and inflorescences were estimated in reproductive stage. Arthropod morphospecies abundance and richness were determined for each treatment. Data were analyzed using uni (ANOVA) and multivariate (CCA) techniques. Arthropods belonging to 7 orders presented a total richness of 48 morphospecies in 2006 and 36 in 2007, while total abundance was 379 in 2006 and 318 in 2007. The proportion of non-herbivores was higher than the proportion of herbivores. Different arthropod communities were observed according to each treatment. No differences were found among treatments in S + W and S total biomass production, while W total biomass and essential oil yield were both different among treatments. Relative biomass production of S and W was the main explanatory variable related to the contrast of arthropod communities between pure annual wormwood (W) and the rest of the treatments. Annual wormwood could be used as an accompanying essential oil crop or left as a weed in the densities tested in this work, favoring biodiversity and, eventually, pest management without compromising soybean crop yield.     

Effects of soil compaction in the sub-humid cropping environment in Pakistan on uptake of NPK and grain yield in wheat (Triticum aestivum): II: Alleviation

Alleviation of soil compaction can be achieved through application of appropriate measures which will vary from soil to soil and with the socio-economic factors of the farmers. The effects of alleviation measures applied to artificially compacted soil on yield components, grain yield, dry matter and nutrient uptake by wheat was studied at the Agriculture Research Institute, Mingora, Pakistan, in two separate experiments in 2002–2003 and 2003–2004. The improvement measures included deep ploughing (DP), farmyard manure (FYM) and gypsum (GYP), and comprised a compacted control and four treatments T1 (control), T2 (DP), T3 (DP + FYM), T4 (DP + gypsum) and T5 (DP + FYM + GYP), arranged in completely randomized block design replicated four times. Improvement measures applied to compacted soil significantly decreased soil bulk density and increased total porosity. Bulk density decreased in the range of 12–15% while total porosity showed an increase of 16–23% over the control. Improvement measures significantly increased concentration and uptake of NPK in both years. Higher concentration and uptake was recorded during the second year as compared to the first year, probably as a result of higher seasonal rainfall in the second year. The uptake of NPK by wheat plants increased in the range of 43–51, 25–94 and 11–28%, respectively, over plants in the compacted control. Similarly, improvement treatments increased grains spike⁻¹, thousand grain weight, dry matter accumulation and grain yield in the range of 14–21, 5–14, 3–10 and 21–37% respectively, over the control. This work demonstrates that it is possible to overcome the deleterious effects of compaction induced by wheeled traffic, and improve crop yields and nutrient uptake in intensive cropping systems in rainfed environments in Pakistan and similar environments.     

Foaming properties of gluten and acetylated gluten: Studies of the mathematical models to describe liquid drainage

The foaming properties of gluten and acetylated gluten were studied at various concentration values (1%, 5%, 10% and 20%). Acetylated gluten was prepared by acetylation of gluten with acetic anhydride in presence of sodium hydroxide as catalyst. The foaming properties were characterised by measuring foam stability and drainage. It was found that foam made from acetylated gluten is more abundant and stable than the foam made from gluten studied in the whole range of concentration, i.e. 1–20%.     

The high yield of irrigated rice in Yunnan,China: ‘A cross-location analysis’

A number of field trials on rice productivity have demonstrated very high yield, but reported limited information on environmental factors. The objective of this study was to reveal the environmental factors associated with high rice productivity in the subtropical environment of Yunnan, China. We conducted cross-locational field experiments using widely different rice varieties in Yunnan and in temperate environments of Kyoto, Japan in 2002 and 2003. The average daily radiation throughout the growing season was greater at Yunnan (17.1 MJ m⁻² day⁻¹ average over 2 years) relative to Kyoto (13.2 MJ m⁻² day⁻¹). The average daily temperature throughout the growing season was 24.7 °C at Yunnan, and 23.8 °C at Kyoto. The highest yield (16.5 tonnes ha⁻¹) was achieved by the F1 variety Liangyoupeijiu at Yunnan in 2003, and average yield of all varieties was 33% and 39% higher at Yunnan relative to Kyoto in 2002 and 2003, respectively. There was a close correlation between grain yield and aboveground biomass at maturity, while there was little variation in the harvest index among environments. Large biomass accumulation was mainly caused by intense incident radiation at Yunnan, as there was little difference in crop radiation use efficiency (RUE) between locations. Large leaf area index (LAI) was also suggested to be an important factor. Average nitrogen (N) accumulation over 2 years was 49% higher at Yunnan than at Kyoto, and also contributed to the large biomass accumulation at Yunnan. The treatments of varied N application for Takanari revealed that the ratio of N accumulated at maturity to the amount of fertilized N was significantly higher at Yunnan than at Kyoto, even though there was no great difference in soil fertility. The Takanari plot with high N application showed a N saturation in plant growth at Kyoto, which might be related to low radiation and relatively high temperatures during the mid-growth stage. These results indicate that the high potential yield of irrigated rice in Yunnan is achieved mainly by intense incident solar radiation, which caused the large biomass and the N accumulation. The low nighttime temperature during the mid-growth stage was also suggested to be an important factor for large biomass accumulation and high grain yield at Yunnan.     

Effect of water management on dry seeded and puddled transplanted rice: Part 2: Water balance and water productivity

Labour and water scarcity in north west India are driving researchers and farmers to find alternative management strategies that will increase water productivity and reduce labour requirement while maintaining or increasing land productivity. A field experiment was done in Punjab, India, in 2008 and 2009 to compare water balance components and water productivity of dry seeded rice (DSR) and puddled transplanted rice (PTR). There were four irrigation schedules based on soil water tension (SWT) ranging from saturation (daily irrigation) to alternate wetting drying (AWD) with irrigation thresholds of 20, 40 and 70 kPa at 18–20 cm soil depth. There were large and significant declines in irrigation water input with AWD compared to daily irrigation in both establishment methods. The irrigation water savings were mainly due to reduced deep drainage, seepage and runoff, and to reduced ET in DSR. Within each irrigation treatment, deep drainage was much higher in DSR than in PTR, and more so in the second year (i.e. after 2 years without puddling). The irrigation input to daily irrigated DSR was similar to or higher than to daily irrigated PTR. However, within each AWD treatment, the irrigation input to DSR was less than to PTR, due to reduced seepage and runoff, mainly because all PTR treatments were continuously flooded for 2 weeks after transplanting. There was 30–50% irrigation water saving in DSR-20 kPa compared with PTR-20 kPa due to reduced seepage and runoff, which more than compensated for the increased deep drainage in DSR. Yields of PTR and DSR with daily irrigation and a 20 kPa irrigation threshold were similar each year. Thus irrigation and input water productivities (WP_I and WP_I+R) were highest with the 20 kPa irrigation threshold, and WP_I of DSR-20 kPa was 30–50% higher than of PTR-20 kPa. There was a consistent trend for declining ET with decreasing frequency of irrigation, but there was no effect of establishment method on ET apart from higher ET in DSR than PTR with daily irrigation. Water productivity with respect to ET (WP_ET) was highest with a 20 kPa irrigation threshold, with similar values for DSR and PTR. An irrigation threshold of 20 kPa was the optimum in terms of maximising grain yield, WP_I and WP_I+R for both PTR and DSR. Dry seeded rice with the 20 kPa threshold outperformed PTR-20 kPa in terms of WP_I through maintaining yield while reducing irrigation input by 30–50%.     

Perennial hybrids of Oryza sativa × Oryza rufipogon: Part II. Carbon exchange and assimilate partitioning

Oryza species differ in their degree of perenniality, which has implications for patterns of carbon distribution in the plant. Interspecific F₁ hybrids of Oryza sativa × Oryza rufipogon were compared with their parental lines to assess whether they differed in assimilate storage and distribution at flowering and after maturity of the first cohort of panicles. The F₁ hybrids varied widely in plant type, but on average they had small plant size and low main tiller weights at anthesis, similar to O. rufipogon, and had intermediate tiller numbers and final single plant weights similar to cultivated rice. O. rufipogon had higher concentrations of starch in stems at anthesis, while interspecific hybrids exhibited comparatively low leaf, stem + sheath, and root sugar concentrations. Near anthesis, substantial ¹⁴C label remained in the source (flag) leaf in O. sativa and F₁ hybrids, while in O. rufipogon more label was exported to sink tissues. The hybrids partitioned more ¹⁴C label to panicles than did cultivated rice and less to leaf sheaths than either parent. Hybrids that had previously been identified as having above-average carbon exchange rates (CER) did not differ consistently from the low-CER hybrids in carbohydrate dynamics. The cultivated species itself maintains some perennial features, and changes in these traits might increase productivity.     

Homogeneous lauroylation of ball-milled bamboo in ionic liquid for bio-based composites production: Part I: Modification and characterization

Ball-milled bamboo meal was completely dissolved under constant conditions (130 °C, 6 h) in the ionic liquid ([C₄mim]Cl) and then the lauroylation was carried out at different conditions. The various factors, such as molar ratio and temperature, were investigated to evaluate the effect of modification. Results showed that the molar ratio played a very important role for the lauroylation. The weight percent gain (WPG) ranged from 167% to 528% when the molar ratio increased from 1.0 to 2.0 for 2 h. It has been shown that the highly substituted bamboo derivatives could be obtained by reacting bamboo meal with lauroyl chloride as the molar ratio is 2.0. All reactions were performed under mild conditions, low excess of reagent and a short reaction time as compared to the heterogeneous chemical modification. The physicochemical properties of the bamboo derivatives were also widely investigated. Results obtained from FTIR and NMR spectroscopies confirmed that the lauroylated derivatives were successfully synthesized in one step. It was also found that thermal stability of the esterified derivatives is lower than that of the unmodified bamboo meal. Moreover, the morphological properties of the esterified bamboo meal were significantly changed by chemical modification. The rough appearance of bamboo meal changed into a relatively homogeneous and smooth surface morphology after lauroylation. Furthermore, the lauroylated bamboo meal had excellent solubility in chloroform, which provides feasibility to electrostatic spinning of modified bamboo meal as biomaterials for industries.