Abstract
Cover crops (CC) can provide protection from erosion and prevent soil carbon depletion. In many cases CC are fertilized to improve carbon inputs and soil cover, however there are few studies on the residual effect of nitrogen (N) in CC biomass and its contribution to N availability of subsequent crops. In order to elucidate this question, a field experiment with rye as cover crop during fallow for corn was carried out at INTA experimental station Anguil, La Pampa. The four treatments were control (C), and CC fertilized with 0, 40 and 80 kg N ha-1 (N0, N40 and N80), in a completely randomized block design. The fertilized CC treatments were later split at V6 of the corn crop, with applications of 60 and 120 kg N ha-1 for N40 and N80 respectively (N40+60 and N80+120). Dry matter (DM) and nutrient contents of standing CC and their residues was determined at “drying” of CC, planting and harvest of corn. Corn yields were recorded at maturity. Fertilized CC had significantly higher DM and N contents than N0 throughout the sampling period; loss of N from CC residues was 38.1, 43.6, 50.2 kg ha-1 for N0, N40 and N80 respectively, around 90% of this loss occurred between “drying” and planting. Assuming the total N loss from DM, this represented 40, 35 and 22% of total corn N uptake for N0, N40 and N80. The yield response of corn to N40 and N80 was 1.5 and 6.1 Mg ha-1, resulting in N use efficiencies of 0.3 and 0.12 Mg grain per kg N applied, respectively. Fertilizer applied to corn caused yield increases of 5.0 and 1.9 Mg for N40+60 and N80+120, with efficiencies of 0.08 and 0.01 Mg grain per kg N applied, respectively. We concluded that N applied to cover crops could be an efficient practice to enhance N availability for corn.
Highlights
Cover crops have been widely used for weed control (Abdin et al, 2000; Gerowitt, 2003) and have been shown to improve the carbon budget of agricultural production systems (Follett, 2001; Dinesh, 2004; Ding et al, 2006) and improving soil physical properties (Franzluebbers and Stuedemann, 2008)
The treatments consisted in bare fallow 3 levels of nitrogen (N) applied to the Cover crops (CC): 0, 40 and 80 kg ha-1 of N (N0, N40 and N80, respectively) which were applied as a solution of urea and ammonium nitrate (UAN) in the Zadoks 21 stage of the crop
The yield response observed in the N80 treatment represented nitrogen use efficiency (NUE) of 19.9 kg Dry matter (DM) per kg N ha-1
Summary
Cover crops have been widely used for weed control (Abdin et al, 2000; Gerowitt, 2003) and have been shown to improve the carbon budget of agricultural production systems (Follett, 2001; Dinesh, 2004; Ding et al, 2006) and improving soil physical properties (Franzluebbers and Stuedemann, 2008). Preliminary results indicate that in the semiarid Pampa the negative impact of cover crops on water storage would be negligible and no significant yield decrease could be expected (Fernández et al, 2010), coinciding with experiences in other semiarid environments (Fengrui et al, 2000). Under these conditions the efficient management of nutrients in the cover crop cash crop sequence will be crucial to offset the additional cost of cover crop cultivation. Cover crops have been shown to contribute to nitrogen availability of cash crops (Sainju et al, 2006; Mohammadi, 2010; Restovich et al, 2012)ryegrass, oats, barley, vetch, rape seed and forage radish but there are still many uncertainties about the efficiency of nitrogen use that is delivered through the mineralization of cover crop residues, and
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