Effect of phosphorus management in rice–mungbean rotations on sandy soils of Cambodia

Abstract

Nitrogen (N) and phosphorus (P) deficiencies are key constraints in rainfed lowland rice (Oryza sativa L.) production systems of Cambodia. Only small amounts of mineral N and P or of organic amendment are annually applied to a single crop of rainfed lowland rice by smallholder farmers. The integration of leguminous crops in the pre‐rice cropping niche can contribute to diversify the production, supply of C and N, and contribute to soil fertility improvement for the subsequent crop of rice. However, the performance of leguminous crops is restricted even more than that of rice by low available soil P. An alternative strategy involves the application of mineral P that is destined to the rice crop already to the legume. This P supply is likely to stimulate legume growth and biological N2 fixation, thus enhancing C and N inputs and recycling N and P upon legume residue incorporation. Rotation experiments were conducted in farmers' fields in 2013–2014 to assess the effects of P management on biomass accumulation and N2 fixation (δ15N) by mungbean (Vigna radiata L.) and possible carry‐over effects on rice in two contrasting representative soils (highly infertile and moderately fertile sandy Fluvisol). In the traditional system (no legume), unamended lowland rice (no N, + 10 kg P ha−1) yielded 2.8 and 4.0 t ha−1, which increased to 3.5 and 4.7 t ha−1 with the application of 25 kg ha−1 of urea‐N in the infertile and the moderately fertile soil, respectively. The integration of mungbean as a green manure contributed up to 9 kg of biologically fixed N (17% Nfda), increasing rice yields only moderately to 3.5–4.6 t ha−1. However, applying P to mungbean stimulated legume growth and enhanced the BNF contribution up to 21 kg N ha−1 (36% Nfda). Rice yields resulting from legume residue incorporation (“green manure use”–all residues returned and “grain legume use”–only stover returned) increased to 4.2 and 4.9 t ha−1 in the infertile and moderately fertile soil, respectively. The “forage legume use” (all above‐ground residues removed) provided no yield effect. In general, legume residue incorporation was more beneficial in the infertile than in the moderately fertile soil. We conclude that the inclusion of mungbean into the prevailing low‐input rainfed production systems of Cambodia can increase rice yield, provided that small amounts of P are applied to the legume. Differences in the attributes of the two major soil types in the region require a site‐specific targeting of the suggested legume and P management strategies, with largest benefits likely to accrue on infertile soils.

Hidden miners – the roles of cover crops and soil microorganisms in phosphorus cycling through agroecosystems

“…Despite its many benefits, the use of cover cropping by farmers is often less utilized than is desirable. Barriers to adoption include the following: benefits are siteand soil-specific, establishment and management problems exist, and climatic variability can lead to uncertainty in outcome (Ro et al 2016). Water use by the cover crop may be a problem under drought stress, resulting in lower yields and P uptake (Turmel et al 2011).…”

“…Datasets from a single field experiment that had been published in several articles (e.g., yield and soil microbiology in different papers) were merged into a single dataset when possible. Details of the studies used (Weerakoon et al 1992;Medhi and Datta 1996;Boswell et al 1998;Vanlauwe et al 2000;Kabir and Koide 2002;Somado et al 2003;Jensen et al 2005;Rutunga et al 2008;Wang et al 2008;Eichler-Löbermann et al 2008;Oikeh et al 2008;Takeda et al 2009b Ro et al 2016;Pavinato et al 2017) and the extracted data can be found in supplementary material (S1+S2). The data were extracted from the publications using the shareware-tool DataThief III (Tummers 2006) and the open source software Tabula (Aristarán et al 2017).…”

Seasonal soil nitrogen dynamics affect yields of lowland rice in the savanna zone of West Africa

“…Thus, provided the environmental conditions permit it, growing pre‐rice green manures can be efficient in avoiding the build‐up of soil NO 3 ‐N and improve systems N balances, as has been shown in the present study, and earlier for example from rice‐wheat rotations in Nepal ( Becker et al., 2007). While grasses have been reported to be more effective in trapping and recovering soil N than legumes ( Baldwin and Creamer , 2006), substantial amounts of 35 ( Ro et al., 2016), 40 ( Asante et al., 2017), 60 ( Ladha et al., 2000) and up to 120 kg N ha −1 ( Becker et al., 1995) can be provided additionally every year by biological N 2 fixation when integrating adapted legumes into a rainfed rice rotation. Amounts of native soil N saved by transition season legumes or by a temporary N immobilization following the application of straw have been estimated to range from 10 ( George et al., 1998), over 25–30 ( Yu et al., 2014; Asante et al., 2017), and up to > 60 kg N ha −1 ( Becker et al., 2007).…”

“…Such strategies add substantial amounts of biologically‐fixed N when legumes are grown and incorporated as green manure ( Sullivan et al., 2012). Different concepts of native soil N conservation and N addition by biological N 2 fixation, sole, or in combination, have been shown to enhance grain yields in the short‐term ( Becker et al., 1995) and to maintain soil fertility in the longer‐term in rice‐based production systems of the Philippines ( George et al., 1998), Cambodia ( Ro et al., 2016), and Nepal ( Becker et al., 2007).…”

Beans with Benefits—The Role of Mungbean (<i>Vigna radiate</i>) in a Changing Environment

“…Mungbean as green manure [96] China Relative contributions of N to wheat grain from mungbean: 48.4% -68.1%.…”