Growth of Legume Cover Crops under Cassava and Its Effect on Soil Properties

Background: Low soil organic carbon is a constraint to cassava tuber formation. Some legume cover crops could be an alternative to provide organic matter on the cassava field as a source of soil organic carbon. The study was aimed to evaluate the growth of some legume cover crops under cassava and their effects on soil properties. Methods: During September 2017-July 2018 legume cover crops (Calopogonium mucunoides, Centrosema pubescens, Pueraria javanica and the mixed) were planted under cassava variety of Mangu and UJ-5. The land coverage by the legume cover crops was measured monthly from 2 to 10 months after planting. Cassava growth was observed weekly from 8 to 32 weeks after planting. Soil properties were analyzed before planting and at harvesting of cassava. Result: Pueraria javanica was tolerant toward cassava shading. The land coverage was linearly increased along with the growth of cassava. At the end of cassava growth, the land area coverage by this legume cover crop was 98.08%. It produced more organic matter and could maintain soil moisture content than other legume cover crops. P. javanica could consider being a suitable legume cover crop under cassava to improve soil quality.

Introduction of legume cover crops practice in intensive grain corn crop system to mitigate soil threats in the Mediterranean region

<p>In Portugal, grain corn is the main cereal produced, comprising 56% of total cereal yield. It is grown in intensive monoculture cropping systems that may have negative effects on soil quality, affecting long-term fertility and productivity, and therefore the sustainability of production. A promising management practice to mitigate soil degradation is to grow a cover crop during the usual fallow period. This study examined in which extend six species of legume cover crops (forage pea (pisum sativum L), yellow lupin (lupinus luteus), crimson clover (trifolium incarnatum), balansa clover (trifolium michelianum), persian clover (trifolium suaveolens), and arrowleaf clover (trifolium vesiculosum) are suitable to mitigate soil threats in grain corn systems specifically in the Mediterranean region. Specific objectives were to identify the effectiveness of the legume 6 species in improving soil fertility (i.e., soil organic matter content), mitigating nutrient leaching, nutrient recycling, and weed control. The study was performed in the lower Mondego valley in central Portugal. It covered two autumn to spring periods of cover crop cultivation, and assessed changes in soil fertility, dry biomass yield of legumes and weeds, and their associated nutrient content (total nitrogen-phosphorus-potassium).</p><p>In general, the six legume cover crops (LCC) species showed good adaptation to Mediterranean conditions, yielding large amounts of biomass (up to 8 ton/ha for clovers species). At the short term, LCC incorporation into the soil had no clear effect in soil organic matter content. The median uptake of NPK macronutrients for all species was high respectively 176-20-172 kg/ha, due to their generally high biomass production, highlighting their great potential to mitigate nutrient leaching. The capacity of the LCC to provide green manure services enabled a median reduction of 40% of N, 60% of P, and 100% of K supplied by mineral fertilizers necessary to attain a corn grain yield of 12t/ha. LCC showed a good effectiveness in weeds control, although only in the second year of the study. Three clover species (crimson, balansa, arrowleaf) performed best in terms of weed control maintaining weed production below 0.5 ton/ha, vs 3-4 ton/ha in control plots, due to early establishment and/or high biomass production in later growth stages, and avoiding the first application of herbicide in pre-emergent herbicide for grain corn cultivation.</p>

Impact of Ambient and Elevated [CO2] in Low Light Levels on Growth, Physiology and Nutrient Uptake of Tropical Perennial Legume Cover Crops

At early stages of establishment of tropical plantation crops, inclusion of legume cover crops could reduce soil degradation due to erosion and nutrient leaching. As understory plants these cover crops receive limited irradiance and can be subjected to elevated CO2 at ground level. A glasshouse experiment was undertaken to assess the effects of ambient (450 µmol mol−1) and elevated (700 µmol mol−1) levels of [CO2] on growth, physiological changes and nutrient uptake of six perennial legume cover crops (Perennial Peanut, Ea-Ea, Mucuna, Pigeon pea, Lab lab, Cowpea) under low levels of photosynthetic photon flux density (PPFD; 100, 200, and 400 µmol m−2 s−1). Overall, total and root dry biomass, total root length, specific leaf area, and relative growth rates were significantly influenced by levels of [CO2] and PPFD and cover crop species. With few exceptions, all the cover crops showed significant effects of [CO2], PPFD, and species on net photosynthesis (PN) and its components, such as stomatal conductance (gs) internal CO2 conc. (Ci), and transpiration (E). Increasing [CO2], from 450 to 700 μmol mol−1 and increasing PPFD from 100 to 400 μmol ּm−2 ּs−1 increased PN. Overall, the levels of [CO2], PPFD and species significantly affected total water use efficiency (WUETOTAL), instantaneous water use efficiency (WUEINST) and intrinsic water use efficiency (WUEINTR). With some exceptions, increasing levels of [CO2] and PPFD increased all the WUE parameters. Interspecific differences were observed with respect to macro-micro nutrient uptake and use efficiency. With a few exceptions, increasing levels of [CO2] from 450 to 700 μmol mol−1 and PPFD from 100 to 400 μmol m−2 s−1 increased nutrient use efficiency (NUE) of all nutrients by cover crop species.

Light Intensity Effects on the Growth, Physiological and Nutritional Parameters of Tropical Perennial Legume Cover Crops

In the early stages of the establishment of plantation crops such as cacao, perennial legume cover crops provide vegetative cover to reduce soil and nutrient loss by erosion. Light intensity at cover crop canopy levels greatly influences their adaptability and optimum growth. As tree crops mature, understory cover crops suffer from inadequate light intensity. A greenhouse experiment was undertaken with nine perennial legume cover crop species (Calopo, Ea-Ea, Jack Bean, Lab-Lab, Mucuna ana, Mucuna preta, Cowpea, Black Pigeon Pea and Mixed Pigeon Pea) to assess the effects of three photosynthetic photon flux densities (PPFDs, µmol m−2 s−1) 180 (inadequate light), 450 (moderate light) and 900 (adequate light) on growth, physiological and nutrient uptake parameters. PPFD had highly significant effects on leaf, shoot and root growth parameters and increasing the light intensity from 180 to 900 µmol m−2 s−1 increased all growth parameters with the exception of specific leaf area. In all the legume cover crops, increasing the light intensity significantly increased the net assimilation rates (NAR), SPAD index and net photosynthesis (PN) and its components, stomatal conductance (gs), transpiration (E) and vapor pressure deficit (VPD). Cover crop species, PPFD and their interactions significantly affected water flux (Vo) and various water use efficiency parameters (WUETOTAL, WUEINST and WUEINTR). Increasing the PPFD increased the WUE in all of the cover crops. Species and PPFD had highly significant effects on the uptake of macro- and micronutrients. Overall uptakes of all nutrients were increased with increases in the PPFD from 180 to 900 µmol m−2 s−1. With few exceptions, the nutrient use efficiency (NUE) of the nutrients was significantly influenced by species, PPFD and their interactions. Except for Mn, increasing the PPFD from 180 to 900 µmol m−2 s −1 increased the NUE for all the nutrients.

Nitrogen release from shoots and roots of crimson clover, hairy vetch, and red clover

Nitrogen (N) release from legume cover crops is a key N source for subsequent crops in rotation. In this study, chopped fresh shoots or roots (<5 mm) of crimson clover (CC), hairy vetch (HV), and red clover (RC) were incorporated into a 50:50 mixture of air-dried sandy loam soil (<2 mm) and washed builders sand at a rate of 300 mg N kg−1. The mixtures were packed in leaching tubes (four replicates), leached with 100 mL of 5 mmol L−1 CaCl2, and then incubated for 10 wk (22 °C, 0.33 bar matric potential) with weekly leaching. Total N and inorganic N (NH4+ plus NO3−) in leachate were quantified and organic N was determined as the difference between total N and inorganic N. More N was released from shoots (63.4%–70.0% of initial N) than from roots (27.3%–50.7% of initial N). Mineralized organic N and inorganic N followed the first order, single N-pool mineralization model [Nt = N0(1 – e−kt); R2 = 0.94−0.99]. Potentially mineralizable N (N0, as % of initial N) was similar for shoots (CC = 75.1%, HV = 74.2%, and RC = 71.3%), but varied for roots (CC = 36.2%, HV = 52.6%, and RC = 53.0%). The N0 pool in shoots had a half-life (t1/2 = ln 2/k) of 11.0, 9.8, and 15.1 d for CC, HV, and RC, respectively; and a half-life in roots of 23.9, 8.5, and 25.7 d, respectively. Hence, HV released its stored N in both roots and shoots faster than CC and RC. The results in this study would help farmers optimize their choice in legume cover crops and termination times to better synchronize N release with crop uptake.

Reklamasi Lahan Bekas Tambang Timah Berpotensi sebagai Lahan Pertanian di Kepulauan Bangka Belitung

<p><strong>Abstrak</strong>. Lahan bekas tambang timah berpeluang untuk dimanfaatkan sebagai areal pertanian dalam upaya pemenuhan kebutuhan pangan dan mengatasi persoalan lingkungan pasca penambangan. Tujuan makalah ini adalah untuk mengkaji upaya reklamasi lahan bekas tambang timah untuk dijadikan areal pertanian di Kepulauan Bangka Belitung. Luas seluruh izin usaha penambangan (IUP) yang telah diterbitkan oleh pemerintah pusat dan daerah dan dimiliki oleh perseroan di darat sebesar 327.524 ha, sedangkan luas IUP di laut 183.837 ha. Aspek biofisik lahan sangat menentukan keberhasilan reklamasi lahan bekas tambang timah. Pemanfaatan lahan bekas tambang timah sebagai areal pertanian menemui sejumlah kendala biofisik lahan, seperti bentang lahan (lanskap) yang tidak beraturan, hilangnya lapisan atas tanah (top soil), rendahnya status kesuburan tanah, dan terganggunya kualitas air kolong. Selain aspek biofisik, upaya reklamasi juga patut mempertimbangkan aspek sosial ekonomi, seperti status kepemilikan lahan, pengetahuan dan keterampilan petani, dan kelayakan biaya usaha tani. Penyimpanan tanah pucuk, penataan lahan, penggunaan amelioran, pengembangan Legume Cover Crops, implementasi Integrated Farming Systems, dan perbaikan kualitas air kolong di lahan bekas tambang timah diyakini mampu meningkatkan kualitas dan daya dukung lahan bekas tambang timah untuk areal pertanian. Reklamasi lahan bekas tambang timah juga membutuhkan partisipasi aktif masyarakat, pemerintah daerah, dan perusahaan tambang timah. Kegiatan reklamasi yang mampu memberikan manfaat bagi masyarakat setempat untuk berusaha tani di lahan bekas tambang timah dapat dijadikan sebagai salah satu indikator keberhasilan reklamasi pasca penambangan.</p><p><strong>Abstract</strong>. Abandoned tin-mining lands have the potential to be used as agricultural areas in order to fulfill food demand and solve the environmental problems derived from mining activities. The purpose of this paper is to assess the reclamation measures on abandoned-tin mining areas which could be used as agricultural areas in Bangka Belitung Islands. The total areas of the mining business license (IUP) issued by the central and local government and owned by the company are 327,524 ha in inland and 183,837 ha in the sea. Biophysical aspects largely determines the success of reclamation of abandoned tin-mining areas. Utilization of abandoned-tin mining areas as agricultural areas is facing land biophysical constraints, such as undulating landscape, losses of top soil, low soil fertility status, and disruption of water quality of tin-mining pond. In addition to the biophysical aspects, reclamation efforts should also consider the socio-economic aspects, including land ownership status, knowledge and skills of farmers, and the feasibility of the cost of farming systems. Conservation of top soil, arrangement of land, development of legume cover crops, implementation of Integrated Farming Systems, and improvement of water quality in the area under the former tin mine are believed to improve the quality and carrying capacity of abandoned tin-mining areas to be used as agricultural areas. Reclamation of abandoned tin-mining areas also requires the active participation of the community, local government, and tin mining company. Reclamation activities that can provide benefits to local communities for farming in tin mined land can be used as one indicator of the success of the post-mining reclamation.</p>

Nitrogen recovery from fertilizers and cover crops by maize crop under no-tillage system

Crop rotation associated with the use of cover crops promotes the introduction of crop residues to the soil, with direct and indirect effects on the availability of plant nutrients, especially nitrogen (N). The objectives of this study were to estimate the N utilization from 15N-urea and cover crop residues (labelled with 15N) of maize crops grown in succession, and evaluate the effects of the isolated and combined use of cover crops and urea on maize plant height, yield components, and grain yield, grown under a no-tillage system. Field research was conducted in an Oxisol (Rhodic Haplustox), Cerrado (Savannah) phase. The experimental design was a randomized block with 20 treatments and four replications in a 5x4 factorial scheme. The treatments were four cover crops species: sunn hemp (Crotalaria juncea L.), pigeon pea (Cajanus cajan (L.) Millsp), green velvet bean (Mucuna prurens), and millet (Pennisetum glaucum L.) + spontaneous vegetation (fallow in the off-season), combined with four N rates: 0, 30, 90, and 150 kg ha-1, applied at the sowing and topdressing stages. The results showed that legume cover crops provided maize grain yields equivalent to the application of 80-108 kg ha-1 N as urea. The urea N utilization by the maize was at an average of 43.5 % of the applied amount. The results indicate that cover crops, particularly legume cover crops, are an important source of N to non-legume cereals. Legumes used as cover crops can replace nitrogen fertilizers of more than 80 kg ha, which is both environmentally and economically viable for corn production.

Legume Cover Crop Effects on Temperate Sugarcane Yields and Their Decomposition in Soil

Sugarcane is commercially produced on 340,000 ha in the US and is valued at over $1 billion US annually. Cultural practices that improve sugarcane sustainability are needed to maintain yields in fields with degraded soils. Historically, leguminous rotation crops provided organic matter and biologically fixed nitrogen (N) for subsequent sugarcane crops. Currently, sugarcane is usually grown as a monoculture with only a short, 6-month fallow period. The objective of these field studies was to determine how growing cowpea (Vigna unguiculata (L.) Walp.) and sunn hemp (Crotalaria juncea L.) as cover crops during fallow affected the yield of subsequent sugarcane crops. A companion laboratory study investigated the decomposition rate of cover crops in soil at different temperatures. Cowpea and sunn hemp production produced 12.8 t/ha dry matter and 250 kg N/ha. Cowpea generally improved plant cane yields, but the effects of sunn hemp varied. However, neither cowpea nor sunn hemp reduced cane or sucrose yields consistently, and mineral N additions may have a role in mitigating yield gains or losses. Based on laboratory data, the average half-life for cowpea and sunn hemp would be 3 months. Overall, using legume cover crops should be viewed as an important component of sustainable sugarcane practices.