Implications For Crop Production Research Articles

Reduced tillage with residue retention improves soil labile carbon pools and carbon lability and management indices in a seven-year trial with wheat-mung bean-rice rotation

Soil total organic carbon (TOC) is a composite indicator of soil quality with implications for crop production and the regulation of soil ecosystem services. Research reports on the dynamics of TOC as a consequence of soil management practices in subtropical climatic conditions, where microbial carbon (C) loss is high, are very limited. The objective of our study was to evaluate the impact of seven years of continuous tillage and residue management on soil TOC dynamics (quantitative and qualitative) with respect to lability and stratification under an annual wheat-mung bean-rice cropping sequence. Composite soil samples were collected at 0-15 and 15-30 cm depths from a three-replicate split-plot experiment with tillage treatment as the main plots and crop residue levels as the sub-plots. The tillage treatments included conventional tillage (CT) and strip tillage (ST). Residue levels were high residue level (HR), 30% of the plant height, and low residue level (LR), 15%. In addition to TOC, soil samples were analyzed for particulate organic C (POC), permanganate oxidizable C (POXC), basal respiration (BR), specific maintenance respiration rate (qCO2), microbial biomass C (MBC), potentially mineralizable C (PMC), and TOC lability and management indices. The ST treatment significantly increased the TOC and labile C pools at both depths compared with the CT treatment, with the effect being more pronounced in the surface layer. The HR treatment increased TOC and labile C pools compared with the LR treatment. The ST + HR treatment showed significant increases in MBC, metabolic quotient (qR), C pool index (CPI), C lability index (CLI), and C management index (CMI), indicating improved and efficient soil biological activities in such systems compared with the CT treatment. Similarly, the stratification values, a measure of soil quality improvement, for POC and MBC were > 2, indicating improved soil quality in the ST + HR treatment compared with the CT treatment. The ST + HR treatment not only significantly increased the contents of TOC pools, but also their stocks. The CMI was correlated with qCO2, BR, and MBC, suggesting that these are sensitive indicators of early changes in TOC. The qCO2 was significantly higher in the CT + LR treatment and negatively correlated with MBC and CMI, indicating a biologically stressed soil condition in this treatment. Our findings highlight that medium-term reduced tillage with HR management has profound consequences on soil TOC quality and dynamics as mediated by alterations in labile C pools.

Increasing wild bee richness and abundance on sequentially flowering cultivars of a pollinator-dependent crop

Many insects have a crucial role as pollinators in both natural ecosystems and agricultural systems. Reports of declining pollinator populations highlight the question how we can support them. Next to semi-natural habitat, different land use types can provide resources for pollinators. However, whether and how different cultivars of pollinator-dependent crops support pollinator populations has not been studied to date. This preliminary study investigated how the abundance of Osmia cornuta and the richness, abundance and community composition of wild pollinators (i.e. wild bees and hover flies) fluctuates throughout the bloom period of three sequentially flowering sweet cherry (Prunus avium) cultivars. Total pollinator richness and abundance increased throughout the bloom period of the different cherry cultivars. This increase was driven by an increase of wild bee richness and abundance, coupled with a decrease of nest-searching bees. The abundance of O. cornuta was found to increase throughout the bloom period. Furthermore, the composition of the pollinator community was significantly different across the different cultivars. Results of this preliminary study reflect the dynamics of wild bee emergence, mating and nest construction, which results in an increase in pollinator diversity and abundance in spring. This study also provides the first evidence that sequentially flowering cultivars of a pollinator-dependent crop can provide complementary floral resources that support complementary pollinator communities. Given the importance of wild pollinators for crop pollination, these results have implications for crop production and pollinator persistence in agricultural landscapes.

The impact of groundwater depletion on agricultural production in India

India relies on groundwater irrigation to produce staple grain crops that provide over half of the calories consumed by its over 1.3 billion people. While groundwater has helped India achieve grain self-sufficiency, aquifers have been overexploited across much of the country and its implications for crop production are unclear. To understand how groundwater depletion affects staple grain (wheat, rice, maize, pearl millet, and sorghum) production in India, we ran district-level panel regressions using agricultural census, groundwater observation, and gridded weather datasets over a ten-year study period (2004–2013). We find that nationally, declining groundwater levels are associated with significant reductions in yield, cropped area, and production for wheat, rice, and maize in the winter season. Despite the negative impacts of groundwater depletion on crop production, we find little evidence that farmers are switching from planting more water-intensive to less water-intensive grains. Using profit-based decision modeling, we further investigated the effects of agricultural energy prices on crop choice in the monsoon season across Haryana and Punjab, which are responsible for over 60% of India’s grain production, have high electricity subsidies, and have rapidly depleting water tables. We find that eliminating energy subsidies for groundwater pumping would likely not encourage farmers to switch to planting less water-intensive crops, though sensitivity analyses suggest that it could encourage the adoption of increased water conservation efforts. In summary, our analyses reveal a discernable impact of groundwater depletion on crop production in India and suggest that reducing or removing energy subsidies may largely affect water use but not crop choice.

High dependency of chilli fruit set on wild pollinators in southern India

Ongoing pollinator declines threaten the production of many entomophilous crops. Recent reports that yields of animal-pollinated crops in India are increasing less than pollinator-independent ones suggest the occurrence of pollen limitation. We experimentally evaluated if production of the common food crop chilli benefits from insect pollination and if crop production is constrained by lack of pollinators under field conditions. Experiments were conducted in eleven chilli fields distributed across a semi-arid agricultural landscape in Andhra Pradesh, India. The experimental treatments included open controls, open pollen-supplemented flowers, and bagged flowers for pollinator exclusion. The fruit set from the two open treatments (control and pollen supplementation) was about three times higher than that from the exclusion treatment, suggesting strong dependence on insect pollination. Control supplementation treatments did not differ, which suggests that there normally is sufficient pollination for chilli production in the area. Bees contributed 98% of flower visits. Flower visitor abundance correlated with higher fruit set, but only significantly so in the pollen supplemented treatment. While previous studies that are mostly conducted in greenhouse settings suggest that chilli reproduction does not depend much on animal pollination, our field study confirms that presence of animal pollinators increases fruit set. Future research should establish if this also applies to fruit quality and total yield. Our study highlights the importance of field-realistic experiments and warrants research on pollinator dependencies of other crops. The results have implications for crop production in an area where pollinator levels may be sufficiently high for crop pollination today but possibly not in the future due to environmental change.

Deep Learning-Based Forecasting of Groundwater Level Trends in India: Implications for Crop Production and Drinking Water Supply

Despite numerous studies in recent times, there is no consensus on the primary drivers for groundwater storage (GWS) changes over India. Thus, predicting future groundwater level trends seems remot...

Winter annual management to increase nutrient recovery and forage production on dairies

AbstractManagement of manure and cereal rye (Secale cereale L.) has implications for crop production and nutrient cycling. This 1‐yr, full‐factorial experiment conducted in Pennsylvania quantified the effects of three management factors—(a) rye management (RyeM; early‐terminated cover crop [CC] vs. double crop harvested a week later [DC]), (b) manure application method (ManM; unincorporated broadcast manure [BM] vs. shallow disk injected manure [IM]), and (c) fall field operation prioritization (priority; manure priority [MP] manure application in late September with rye planting in mid‐October vs. rye priority [RP], rye planting in late September with manure application in early November)—on rye biomass, nutrient recovery, and forage yield and the effect of ManM and priority on DC forage nutritive value in a rye–corn (Zea mays L.) cropping sequence. This experiment was intended to be a repeated 2‐yr study, but due to MP treatment rye crop failure in the second year, the resulting 1‐yr dataset was analyzed to assess priority effects. Prioritizing rye planting in the fall with DC increased total forage production and apparent N recovery (ANR) when manure was broadcast. These results highlight the value of prioritizing fall rye planting in DC systems to increase rye spring biomass and nutrient recovery when manure is broadcast. More experiments should be conducted on fall field operation timing to develop reliable recommendations.

The effect of water deficit on inflorescence period at palm oil productivity on peatland

Various factors influence palm oil production, including planting material, environment (climate and soil), and cultivation management. The environment occupies a crucial position that can affect crop production potential even with optimal cultivation management. Unfavorable climatic conditions, for instance, drought, can cause water deficit, which has implications for crop productivity. This paper aims to get a comparative study for the effect of water deficit on the inflorescence period, namely the sex determination phase (29 months before harvesting) and floral abortion (10 months before harvesting). The research was carried out on oil palm plantations on peatland in Riau, Indonesia, with the characteristic annual rainfall of 2000 mm/ year. This study employs a simple regression analysis on panel data of five years and two estates for data analysis. The result highlights that the increase of a 100 mm water deficit on oil palm peatland plantation impacts the decrease in productivity by 6% in the sex determination phase. In contrast, in the floral abortion phase, the decline in productivity is more significant, namely 7%. The analysis also indicated that the research deficit had more impact on the bunch number than the bunch weight.

Functional Dissection of the Chickpea (Cicer arietinum L.) Stay-Green Phenotype Associated with Molecular Variation at an Ortholog of Mendel's I Gene for Cotyledon Color: Implications for Crop Production and Carotenoid Biofortification.

“Stay-green” crop phenotypes have been shown to impact drought tolerance and nutritional content of several crops. We aimed to genetically describe and functionally dissect the particular stay-green phenomenon found in chickpeas with a green cotyledon color of mature dry seed and investigate its potential use for improvement of chickpea environmental adaptations and nutritional value. We examined 40 stay-green accessions and a set of 29 BC2F4-5 stay-green introgression lines using a stay-green donor parent ICC 16340 and two Indian elite cultivars (KAK2, JGK1) as recurrent parents. Genetic studies of segregating populations indicated that the green cotyledon trait is controlled by a single recessive gene that is invariantly associated with the delayed degreening (extended chlorophyll retention). We found that the chickpea ortholog of Mendel’s I locus of garden pea, encoding a SGR protein as very likely to underlie the persistently green cotyledon color phenotype of chickpea. Further sequence characterization of this chickpea ortholog CaStGR1 (CaStGR1, for carietinum stay-green gene 1) revealed the presence of five different molecular variants (alleles), each of which is likely a loss-of-function of the chickpea protein (CaStGR1) involved in chlorophyll catabolism. We tested the wild type and green cotyledon lines for components of adaptations to dry environments and traits linked to agronomic performance in different experimental systems and different levels of water availability. We found that the plant processes linked to disrupted CaStGR1 gene did not functionality affect transpiration efficiency or water usage. Photosynthetic pigments in grains, including provitaminogenic carotenoids important for human nutrition, were 2–3-fold higher in the stay-green type. Agronomic performance did not appear to be correlated with the presence/absence of the stay-green allele. We conclude that allelic variation in chickpea CaStGR1 does not compromise traits linked to environmental adaptation and agronomic performance, and is a promising genetic technology for biofortification of provitaminogenic carotenoids in chickpea.

Spatiotemporal trend analysis of rainfall and temperature, and its implications for crop production

Abstract Global warming is a significant global environmental problem in the 21st century. The problem is high in developing countries, particularly sub-Saharan countries in which the majority of the population live on rainfed agriculture. The present study aimed to undertake spatiotemporal analysis of seasonal and annual rainfall and temperature and its implications. The MK test, Sen's slope and precipitation concentration index (PCI) were applied. Finally, Pearson correlation analysis between climatic variables and crop production was analysed. The Mann–Kendall test results showed that the annual and seasonal rainfall trend was highly variable. The minimum and maximum temperatures have increased by 0.8 and 1.1 °C/year, respectively. Based on PCI results, rainfall during the summer and spring seasons is moderately distributed as compared to annual and winter season rainfall. Based on these observations, the rainfall pattern and distribution of the area could be classified as irregular and erratic distribution. Results of correlation analysis between monthly and seasonal rainfall with crop production were insufficient to conclude the impact of rainfall and temperature on crop production. In view of this, the incidence of food shortage is a common occurrence. Therefore, depending on the historical trend of rainfall variability and prolonged temperature increase, appropriate coping and adaptation strategies need to be encouraged.

Recent warming across the North Atlantic region may be contributing to an expansion in barley cultivation

Although grass dominates most agricultural systems in the North Atlantic region (NAR), spring barley is the most important cereal and is used for animal feed and food and drink products. Recent changes in climate have resulted in warmer conditions across the NAR which have major implications for crop production. In this paper, we investigate the thermal requirement of spring barley in the region and use the results to examine the effects of recent trends in temperature and rainfall on barley cultivation, based on 11 regional meteorological sites. At these sites, between 1975 and 2015, we found significant warming trends for several months of the cropping season and significant trends for increases in the cropping season degree days (CSDD). In recent years, this has resulted in an increased proportion of years when the estimated minimum thermal requirement for barley has been met at sites above about 60°N. However, annual variations in CSDD are large and years still occur at these sites where this is insufficient. While warming could potentially allow an earlier start and later end to the cropping season, it is likely that high rainfall at maritime sites, and low rainfall at continental sites, will limit the ability of growers to benefit from this. Warming is considered to have been one of the main factors contributing to the large expansion of the area of barley cultivated in Iceland since the 1990s.

Spatial distribution of soil chemical properties in an organic farm in Croatia.

Soil pH, electrical conductivity (EC), organic matter (OM), available phosphorus (AP), and potassium (AK) are some of the most important indicators of soil fertility. These soil parameters are highly variable in space and time, especially in agricultural areas, with implications for crop production. The aim of this work was to study the spatial variability of pH, EC, OM, AP and AK using kriging and co-kriging methods in the Rasa River Valley (Croatia). As co-variates for each variable we considered the distance from the sea (DFS), distance from the river channels (DFC), pH, EC, OM, AP and AK. Only the variables with a significant correlation with the predictor were used as predictor variables. The results showed that soils of the study area had high pH, EC, OM and AK values and a low concentration of AP. The spatial variability was high for EC and low for pH levels. pH, EC, OM and AK had significant positive correlations. All these variables had significant negative correlations with AP. The exponential model was the best to model OM, AK and AP. Spherical and Gaussian models were the most accurate to model pH and EC. Spatial dependence was high for soil AK, EC and pH, and moderate for soil OM and AP. The incorporation of auxiliary variables increased the precision of the estimations. CoK_DFS was the best method to predict soil EC and AP, while Cok_EC, was better to estimate soil pH and Cok_pH and Cok_OM predicted soil OM and AK with the best accuracy. The maps produced with the best predictors showed that pH, EC, OM and AK had high levels in the northern and eastern parts of the study area. The opposite trend was identified in relation to the AP spatial pattern.

Intensity of heat stress in winter wheat—phenology compensates for the adverse effect of global warming

Higher temperatures during the growing season are likely to reduce crop yields with implications for crop production and food security. The negative impact of heat stress has also been predicted to increase even further for cereals such as wheat under climate change. Previous empirical modeling studies have focused on the magnitude and frequency of extreme events during the growth period but did not consider the effect of higher temperature on crop phenology. Based on an extensive set of climate and phenology observations for Germany and period 1951–2009, interpolated to 1 × 1 km resolution and provided as supplementary data to this article (available at stacks.iop.org/ERL/10/024012/mmedia), we demonstrate a strong relationship between the mean temperature in spring and the day of heading (DOH) of winter wheat. We show that the cooling effect due to the 14 days earlier DOH almost fully compensates for the adverse effect of global warming on frequency and magnitude of crop heat stress. Earlier heading caused by the warmer spring period can prevent exposure to extreme heat events around anthesis, which is the most sensitive growth stage to heat stress. Consequently, the intensity of heat stress around anthesis in winter crops cultivated in Germany may not increase under climate change even if the number and duration of extreme heat waves increase. However, this does not mean that global warning would not harm crop production because of other impacts, e.g. shortening of the grain filling period. Based on the trends for the last 34 years in Germany, heat stress (stress thermal time) around anthesis would be 59% higher in year 2009 if the effect of high temperatures on accelerating wheat phenology were ignored. We conclude that climate impact assessments need to consider both the effect of high temperature on grain set at anthesis but also on crop phenology.

Crop diversification as a smallholder livelihood strategy within semi-arid agricultural systems near Mount Kenya

Crop diversification is one strategy that smallholder farmers may employ to reduce their vulnerability in the face of global environmental change. Diversification not only expands the number of potential crop types for market, it also improves agroecosystem functioning by building redundancy into the agricultural system and allowing for innovation in areas exhibiting impacts of climate variability. While the driving forces behind and impacts of crop diversification have been extensively investigated, there are particular issues for the prospects of crop diversification to reduce household vulnerability within semi-arid agricultural systems. The decision to diversify crops is a particularly challenging one for farmers in semi-arid systems. Semi-arid systems can exhibit greater variability in annual precipitation in areas that are marginal for agricultural production. Changes to the timing of the growing season (onset of rains) and mid-season dry periods in particular pose significant challenges to farmers in semi-arid ecosystems. This paper examines the spatial diversification of crop types across an upland-lowland gradient on Mount Kenya's northwestern slopes. We perform regression analyses using household-level survey data collected during the summer of 2012 to investigate the factors contributing to varying levels of crop diversification and implications for crop production in a semi-arid irrigated agricultural system. We hypothesize that the study area locations at higher elevations will be able to grow a greater variety of crops due to climate suitability. Our analysis demonstrates that household-level income, field size, exposure to agricultural extension officers, and suitability of environmental conditions are related to the likelihood of smallholder crop diversification. More favorable growing conditions appear to outweigh limitations posed by inaccessibility and financial constraints, which has implications for adaptation to climate change in semi-arid ecosystems. We discuss the results in the context of challenges posed by global environmental change.

Tinkering on the periphery: Labour burden not crop productivity increased under no-till planting basins on smallholder farms in Murehwa district, Zimbabwe

No-till planting basins are promoted using seed and fertiliser inputs as incentives for their widespread uptake in Zimbabwe. The short term effects of planting basins on crop yields and labour requirements were evaluated in an on-farm experiment over two seasons (2009/2010 and 2010/2011) in Murehwa district, Zimbabwe. The experiment was established on clay (Luvisols) and sandy soils (Lixisols), in two field types; outfields (degraded) and homefields (better managed fields). Fields closest to homesteads (homefields) typically receive most nutrients and preferential management, and are more fertile than outlying fields (outfields), with implications for crop production and nutrient use efficiencies. The fertiliser sub-treatments consisted of (a) no fertiliser (control), (b) 60kg N+3tmanureha−1, (c) 60kgNha−1+10kgPha−1 (SSP) and (d) 60kgNha−1+20kgPha−1 (SSP). In addition, a socio-economic survey was carried out to understand the diversity in resource ownership among farmers and to explore whether there was a relationship with uptake of planting basins. Results showed that field type, nutrient application and season had a significant effect on crop yields (p<0.001); there was no significant effect of tillage practice. The largest maize grain yield of 5.6tha−1 was obtained with a combination of manure (3tha−1) and 60kgNha−1 under conventional tillage; the equivalent treatment under planting basins yielded 4.6tha−1 in the 2009–2010 season. Rainfall was poorly distributed in 2010–2011 season and the same treatment gave the largest grain yield of 1.6tha−1 under conventional tillage and 1.2tha−1 under no-till planting basins. Land preparation under conventional tillage required 6mandaysha−1 while planting basins construction required 76.5mandays’ha−1 for the clay soils and 51.5mandaysha−1 for the sandy soils. Weeding in planting basins required 40% more labour compared with conventional tillage (12mandaysha−1) due to greater weed densities associated with early years of no-tillage. Planting basins did not enhance moisture conservation in a the 2010–2011 season when rainfall was poorly distributed as shown by the smaller yields. The increased labour requirements suggested a major impediment to the uptake of planting basins even for farmers without livestock. Farmers differed greatly in resource ownership; four resource groups were identified based on land size, cattle ownership, labour availability and land utilisation. However, the practice of planting basins did not relate to resource ownership due to the incentives provided by the NGOs. Given that planting basins increased the labour burden but not crop yield, and that incentives cannot go on forever, widespread adoption by smallholder farmers seems unlikely.

Cellular Mechanisms in Higher Plants Governing Tolerance to Cadmium Toxicity

Cadmium (Cd) is an inorganic mineral in the earth's crust. Cadmium entry into the environment occurs through geogenic and anthropogenic sources. Industrial activities including mining, electroplating, iron and steel plants, and battery production employ Cd during their processes and often release Cd into the environment. When disseminated into soil, Cd can be detrimental to agro-ecosystems because it is relatively mobile and phytotoxic even at low concentrations. Cadmium's phytotoxicity is due to reductions in the rate of transpiration and photosynthesis and chlorophyll concentration resulting in retardation of plant growth, and an alteration in the nutrient concentration in roots and leaves. In response to Cd toxicity, plants have developed protective cellular mechanisms such as synthesis of phytochelatins and metallothioneins, metal compartmentalization in vacuoles, and the increased activity of antioxidant enzymes to neutralize Cd-induced toxicity. While these direct protective mechanisms can help alleviate Cd toxicity, other indirect mechanisms such as microelements (zinc, iron, manganese, and selenium) interfering with Cd uptake may decrease Cd concentration in plants. This comprehensive review encompasses the significance of Cd, portals of contamination and toxicity to plants, and implications for crop production. Various mitigation strategies with the beneficial effects of zinc, iron, manganese, and selenium in activating defence mechanisms against Cd stress are discussed. Furthermore, this review systematically identifies and summarises suitable strategies for mitigating Cd-induced toxicity in plants.

The effect of total carbon on microscopic soil properties and implications for crop production

Soil structure is a dynamic property affected by physical, chemical, and microbiological processes. Addition of organic matter to soils and the use of different management practices have been reported to impact soil structure and crop production. Moderation in soil temperature and increases in microbial activity and soil water retention are often suggested as reasons for the rise in crop yield when organic matter is added to the soil. Less is known about the direct effect of changes in soil structure on crop production. A field experiment was conducted to study the effect of summer cover crop and in-season management system on soil structure. The experiment was a nested design with summer cover crop as the main plot and management system as the subplot. Summer cover crop treatments included cowpea (Vigna unguiculata L. Walp.) incorporated into the soil in the fall (CI), cowpea used as mulch in the fall (CM), sudangrass (Sorghum vulgare) incorporated into the soil in the fall (S), and dry fallow or bare ground (B). Management systems were organic (ORG) and conventional (CNV) systems. Lettuce (Lactuca sativa L.) and cantaloupes (Cucumis melo L.) were cultivated in rotation in the plots for three consecutive years using the same cover crops and management systems for each plot. Disturbed and undisturbed soil cores were collected at the end of the third year and used for laboratory experiments to measure physical, chemical, and hy- draulic properties. Image analysis was used to quantify soil structure properties using a scanning electron micro- scope on thin sections prepared from the undisturbed soil cores. We found that total soil carbon was correlated with porosity, saturation percentage, and pore roughness. Pore roughness was correlated with crop production in gen- eral and with marketable production in particular. We found that the higher the complexity of the pore space, the more water retained in the soil, which may increase soil water residence and reduce plant water stress.

Climate Impacts on Agriculture: Implications for Crop Production

Changes in temperature, CO2, and precipitation under the scenarios of climate change for the next 30 yr present a challenge to crop production. This review focuses on the impact of temperature, CO2, and ozone on agronomic crops and the implications for crop production. Understanding these implications for agricultural crops is critical for developing cropping systems resilient to stresses induced by climate change. There is variation among crops in their response to CO2, temperature, and precipitation changes and, with the regional differences in predicted climate, a situation is created in which the responses will be further complicated. For example, the temperature effects on soybean [Glycine max (L.) Merr.] could potentially cause yield reductions of 2.4% in the South but an increase of 1.7% in the Midwest. The frequency of years when temperatures exceed thresholds for damage during critical growth stages is likely to increase for some crops and regions. The increase in CO2 contributes significantly to enhanced plant growth and improved water use efficiency (WUE); however, there may be a downscaling of these positive impacts due to higher temperatures plants will experience during their growth cycle. A challenge is to understand the interactions of the changing climatic parameters because of the interactions among temperature, CO2, and precipitation on plant growth and development and also on the biotic stresses of weeds, insects, and diseases. Agronomists will have to consider the variations in temperature and precipitation as part of the production system if they are to ensure the food security required by an ever increasing population.

Effects of level soil bunds and stone bunds on soil properties and its implications for crop production: the case of Bokole watershed, Dawuro zone, Southern Ethiopia

Level soil bunds (LSB) and stone bunds (SB) have been widely implemented in the Bokole watershed since 2000 through support of the World Food Program (WFP). However, the performance of them against the target of the structure has not been studied. This study analyzed the effect of LSB and SB on selected soil properties, when compared with nonterraced cropland. The Bokole watershed was divided into two units. From upper watershed, three croplands with LSB (aged 4, 6, and 9 years) and three nonterraced croplands each adjacent to one of the LSB were selected. Similarly, in lower watershed, SB aged 4, 6, and 8 years and three nonterraced croplands each adjacent to one of the SB were selected. From each cropland with LSB and SB, three composite soil samples (rep licates) were collected systematically in X designed rectangular plot. From each nonterraced cropland, three composite soil samples (replicates) were collected in X designed square plot. A total of 36 soil samples were analyzed for Soil Organic Carbon (SOC), Total Nitrogen (TN), Available Phosphorus (AP), Available Potassium (AK), pH, and Cation Exchange Capacity (CEC) following standard laboratory procedures. Most soil parameters were not significantly different in cropland with LSB and SB compared to nonterraced. However, in LSB aged 4 years and SB aged 6 years AP and pH were significantly less than their adjacent-nonterraced cropland. In SB aged 8 years, SOC, AP, AK, and pH were also significantly less than adjacent-nonterraced cropland. Past erosion, and past land uses are likely factors contributed to the observed result. It was inferred that the mean con tribution of LSB and SB alone for crop production with regard to analyzed soil parameters was not significant in the considered sites. Additional soil fertility management practices should be incorporated for better effect.

Rice root growth and physiological responses to SRI water management and implications for crop productivity

This paper reports on several research findings on rice root responses, in terms of growth and physiology, manifested when applying System of Rice Intensification water management principles under semi-field and field conditions, in conjunction with variations in plant density and microbial density in the soil. The research aimed to learn about causal relationships, if any, between rice root and shoot growth at different growth stages of the rice plant’s development and their cumulative effect on yield, which is affected by both biotic and abiotic influences. It was seen that greater root length density and a higher rate of root activity affected the yield-contributing parameters in all of the trials, whether conducted under semi-field or field conditions. At the same time, both root parameters were significantly affected by the water regime, soil microbial density, and planting pattern, the three main factors considered. The most important finding observed under semi-field conditions was that enhanced microbial density in the soil improved the sink capacity of the rice plants under all water regimes evaluated. Positive correlations were found between the chlorophyll content of the flag leaf and the duration of grain filling, between the chlorophyll content of plants’ lower leaves and their roots’ oxidizing activity rate, and the roots’ oxidizing activity rate at later growth stage and the available soil nitrogen. These relationships can significantly improve rice plants’ physiological efficiency and hence grain yield, provided that soil nutrients are not a limiting factor and when source–sink demand is maintained simultaneously. To realize the highest crop yield per hectare, both planting pattern and spacing are factors that need to be optimized. This paper in its conclusion considers the relevance of exploiting roots’ potential for plasticity to enhance crop productivity in the context of impending water constraints and climate-change effects.

The risk of vegetative water deficit in early-sown faba bean (Vicia faba L.) and its implications for crop productivity in a Mediterranean-type environment

Farmers in Mediterranean-type environments should plant annual crops as early as possible to maximise yield. Greater rainfall variability at the start of the growing season potentially exposes early-sown crops to water deficit, which may be severe enough to cause crop mortality or to reduce potential productivity. This paper shows that in a typical Mediterranean-type environment at Merredin, Western Australia, much longer dry periods between rainfall events are likely in April rather than in May or June, but with a sowing rule based on farmer behaviour the likelihood of damaging water deficit is small. Soil water at sowing is a good indicator of this likelihood. The implications of early water deficit for crop productivity were investigated for faba bean in two experiments at Merredin in 1997 and 1998. In 1997 simulated plant available water in the top 40 cm (PAW40) at sowing was 24 mm and 8-week-old plants displayed severe wilting after 6 weeks without rain. There was no crop mortality even after 8 weeks without rain and plants recovered quickly when rewatered. Water deficit reduced grain yield through lower evapotranspiration since withholding water reduced total supply but also because severely stressed plants could not extract water from as deep in the soil as less stressed plants. In 1998 simulated PAW40 at sowing was 41 mm and no wilting was observed when water was withheld for 8 weeks. Apparent transpiration efficiency was not affected by mild water deficit in either year, but was reduced by 35% by delaying sowing in 1998. This was due to higher atmospheric vapour pressure deficit during reproductive growth of the later-sown crop. These results suggest that delaying sowing in faba bean is more likely to reduce faba bean grain yield unless there is a strong likelihood of severe water deficit soon after sowing. This likelihood can be judged from the amount of soil water at sowing.