NITROGEN UPTAKE AND RECOVERY FROM N FERTILIZER AND LEGUME CROPS IN WETLAND RICE MEASURED BY¹⁵N AND NON-ISOTOPE TECHNIQUES

Abstract

2 Intensive rice-based cropping systems rely on nitrogenous fertilizer for optimum grain production and legume crops could be used as an alternative nitrogen (N) source for rice. We investigated the fate of N applied to dual cropping wetland rice in the form of legume residue and 15 N labeled fertilizer. In 2001 -2002, hairy vetch and broad bean accumulated 131 and 352 kg N ha −1 of which 41 and 78% was derived from N 2 fixation. In 2002 -2003, hairy vetch accumulated 64 kg N ha −1 and broad bean accumulated 320 kg N ha −1 of which 21 to 24% was derived from hairy vetch and 31 to 82% N was derived from broad bean by N difference and 15 N-natural abundance method. Our results reveal that hairy vetch and broad bean can supply 50 -100% of N required for intensive wetland rice and can be a viable alternative N source to enhance soil fertility.

Tropical Legume Crop Rotation and Nitrogen Fertilizer Effects on Agronomic and Nitrogen Efficiency of Rice

“…Nitrogen uptake in the different legume species vary according to the influence of biomass production and N content in the plant tissues. Earlier studies have reported that faba bean produced >10 kg biomass m −2 which recorded >35 g N m −2 [ 33 ]. Other studies have also reported that N uptake by cover crops produced 4.5 to 22.5 g of N per m −2 [ 42 – 44 ].…”

“…Our results suggest that legume residues had a positive influence on both rice yield and N uptake when fertilizer was not used. Certainly, the influence of legume residues on rice yield depends on the soil nutrient status, texture, addition of organic matter, amount of residue returned to soil [ 33 ], and timing and levels of fertilizer N used.…”

“…Incorporation of crop residues alters the soil environment that in turn influences the microbial population's activity in the soil and subsequent nutrient cycle [ 23 ] and will sustain rice productivity through replenishing soil organic matter [ 32 ]. The presence of soil organic matter is a key indicator of soil quality, which provides plant nutrients upon mineralization and eventually improves soil properties [ 33 ].…”

Increasing global crop harvest frequency: recent trends and future directions

“…Furthermore, high CHF has been found as a risk aversion and crop productivity boosting strategy under climate change conditions in many sub-Saharan African countries [69]. If the first crop is a nitrogen fixer, and the second non-N-fixing crop, overall yields improve under such increased CHF [70][71][72], at least in the short term. Increasing CHF could also increase farmer incomes, break the life cycle of pathogens and pests [73], and reduce chemical application especially in no-till agricultural practices [29].…”